@article { author = {Miri, Parvin and Rashki, Alireza and Sepehr, Adel}, title = {Spatial and Temporal Variability of Aerosol Indices over East Khorasan, Iran based on Satellite Observation}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {1-20}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.54464}, abstract = {1. Introduction Satellite remote sensing provides an undoubtedly unique opportunity to extract spatial patterns of regional, international and seasonal aerosol properties. In order to understand the effects of air particles on climate and human health over the lands, it’s necessary to have spatial and temporal distribution of aerosol. Ground-based measurement data do not provide the spatial pattern of particles and therefore, satellite data are used. Aerosol indices such as Aerosol Index (AI) and Aerosol Optical Depth (AOD) are commonly used to identify the amount of atmospheric particles. East Khorasan is under the influence of dust emission since the strong Levar winds (120-day wind) blow over the region. The aim of this study was to investigate the temporal and spatial variability of aerosol in the East Khorasan, Iran based on satellite data. 2. Study Area East Khorasan with an area of 100,161 km2 is limited from the north and east to Turkmenistan and Afghanistan and from south to Sistan and Baluchistan Province. There are 11 meteorological stations at this region including Sarakhs, Mashhad, Torbat-e-Heydarieh, Torbat-e-Jam, Taybad, Khaaf, Gonabad, Qaen, Birjand, Sarbishe and Nehbandan. 3. Material and Methods The Aerosol indices were obtained from TOMS sensors with a spatial resolution (1^°×〖1.25〗^°) and OMI sensors with a spatial resolution (〖0.25〗^° 〖×0.25〗^°) from http://disc.sci.gsfc.nasa.gov/giovanni. The monthly, seasonal and yearly mean values of the data sets were calculated from all available data. To study atmospheric aerosols, UVAI, AOD and AAOD indices were used. For this purpose, TOMS sensor data from the satellite Nimbus 7 satellite in 1978 and 1993 and in 1996 and 2005 and the Earth probe OMI on Aura satellite were used from 2004 to 2014. 4. Results and Discussion The results indicated that the amount of particulate matter obtained using UVAI/OMI is highest in all cities in June, July and April and lowest in December, November, and October. The AAOD related to each city was quite different from other cities and there was no specific month which showed the highest or the lowest concentration of absorbing particles; it seems that the UVAI index does not follow a specific pattern while the UV index has the highest amount in Mashhad. Therefore, UV seems to be associated with air pollution. AOD index also had the highest value in the city of Mashhad in May and the lowest value occurred in Tayabad and then in Khaaf in December. Maximum UVAI/TOMS index occurred in June. The OMI sensor has the same monthly pattern as the TOMS data. Tayabad had the highest aerosol (UVAI) and Mashhad had the lowest. From 2004 to 2014, the amount of aerosol increased in the region. The concept of AAOD is close to UV-absorbing aerosols such as smoke, dust and minerals in all cities increased in the period of 11 years. 5. Conclusion According to the results, spatial and temporal variabilities of indices are more associated with climate processes and then topography. Low attitude areas have the highest UVAI aerosol value while mountainous areas have the lowest amount of UVAI index.}, keywords = {Aerosol indices,East Khorasan,TOMS sensor,OMI sensor}, title_fa = {بررسی تغییرات زمانی و مکانی شاخص‌های گرد‌و‌غبار در شرق خراسان بر پایۀ داده‌های ماهواره‌ای}, abstract_fa = {ذرات معلق در هوا نقش مهمی در توازن انرژی زمین و جو ایفا می‌کنند و به عنوان یک عامل مهم در تعیین تغییرات آب‌وهوایی شناخته می‌شوند. هرساله طوفان‌های گرد‌و‌غبار اثرات مخربی بر روی سلامت، مزارع، تأسیسات و اکوسیستم‌ها می‌گذارند. خراسان ازجمله مناطقی است که به‌شدت تحت تأثیر این پدیده قرار دارد و بادهای 120 روزه سیستان از عوامل تشدید‌‌کننده این پدیده بخصوص در مناطق شرقی است. یکی از راه‌های مطالعۀ این پدیده روش‌های سنجش‌ازدوری است. این تحقیق با هدف بررسی تغییرات زمانی و مکانی شاخص‌های گرد‌و‌غبار بر پایه داده‌های ماهواره‌ای در منطقۀ شرق خراسان انجام پذیرفته‌ است. در این پژوهش جهت مطالعۀ ذرات معلق جو، از شاخص‌های UVAI،AAOD و AOD استفاده شده است. برای این منظور از داده‌های سنجندۀ TOMS بر روی ماهوارۀ Nimbus 7 در سال‌های 1978 تا 1993 و بر روی ماهوارۀ Earth probe در سال‌های 1996 تا 2005 و از داده‌های سنجنده OMI بر روی ماهوارۀ Aura از سال 2004 تا 2014 استفاده شده است. نتایج این پژوهش روند صعودی این شاخص‌ها را در طی سال‌های‌ 2014-1978 نشان می‌دهد.‌ همین‌طور شاخص UVAI بیشترین میزان ذرات معلق را در سال‌های 2002، 2008 و 2014 و شاخص‌های AAOD و AOD بیشترین میزان ذرات معلق را در سال‌های 2008 و 2014 نشان می‌دهند.}, keywords_fa = {شاخص‌های گرد‌و‌غبار,شرق خراسان,سنجنده‌ی TOMS,سنجنده‌ی OMI}, url = {https://geoeh.um.ac.ir/article_31301.html}, eprint = {https://geoeh.um.ac.ir/article_31301_e1303e4c5365ef423e60ceb7fbd16caf.pdf} } @article { author = {Yarahmadi, Dariush and Sharafi, Siyamack}, title = {The Assessment of Natural Hazards of Khorramabad-Pol-e-Zal Freeway with the Passive Defense Approach}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {21-45}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.57408}, abstract = {1. Introduction Transport network, as a basic infrastructure, is of economic, social, and political importance to any country. Among the various ways of transport (that is, road, rail, air, and sea), road transport, due to its unique features, basically is known to be the most commonly used one. Nowadays, one of the important ways to bring down an under-attack country is to seriously damage its vital arteries (i.e. roads and transportation ways). Therefore, in order to defend a country against such attacks, it is imperative to know how to deal with them. Passive defense, as one of the influential factors in many projects, is one of the most effective and sustainable ways to defend against such threats. It refers to a number of strategies, utilization of which in the design and construction of facilities and biological buildings, automatically increases the defense power of the construction without pressuring the human resources, and, as a result, decreases the possibility of crisis. One of the factors contributing to passive defense is paying attention to geological features when locating and routing facilities and constructions. Slope instabilities are among such phenomena that are related to geological features; in addition to road blockage, these instabilities cause the parts on which facilities and structures are built to move and be displaced. Based on the aforementioned argument, it is imperative to consider the geological features while building infrastructures such as roads; it is also crucial to evaluate active geological forms and phenomena, having passive defense in mind, when locating and routing such infrastructures in order to minimize the risk of damage made by geological movements to them. In this regard, Khorram abad-Pole Zal Freeway as the main south-north road artery of the country that has a diverse range of natural hazards due to its geological characteristics is studied using the passive defense approach. Khorrram abad-Pole Zal Freeway, the area of study, as part of Tehran-Bandar Imam Khomeini’s route, has a length of about 104 km. The freeway extends from some parts of Lorestan Province (that is, Dore-Chegeni and Poldokhtar) to Andimeshk in Khuzestan Province. The path starts from the latitude of 33˚ 25′ and the longitude of 48˚ 12′ east and ends at the latitude of 33˚ 48′ North and the longitude of 48˚ 03′ east. 2. Material and Methods The present study has used an applied research type; moreover, for the research method of the study, the analytical field studies method was employed. Data were gathered using data from both library and field studies methods. Library resources were tapped on in order to make theoretical assessments and to develop a theoretical framework of the research literature. In the field studies that form the fundamentals of the present research, the freeway was firstly studied to identify the natural hazards that endanger the path. Afterwards, using GPS, hazardous places along with places were landslides had occurred were identified. The rest of the qualitative and quantitative data from hazardous points were collected in field studies. In the present study, physical tools such as geological maps of 1: 100000, topographic maps of 1: 25000, digital elevation model with a resolution of 30 meters, satellite images (Landsat-Sensor TM and ETM), images of Google Earth, conceptual tools such as software Arc GIS, ENVI, Google Earth, and other similar software were used to create a database; satellite imagery, spatial analysis and map drawing have also been employed in the study. After providing the basic information, the hazardous places along with the identified hazardous points, according to the data gathered from the field studies, were prioritized using Delphi method and the opinion of experts in Geological Sciences. Finally, the hazards were analyzed after dividing them into different sections according to their risk level. 3. Results and Discussion The survey of Khorram abad-Pole Zal Freeway and its surrounding areas indicated that mass movements, landslides, and collapses occur frequently in the given areas. Based on the field studies, 21 active landslide zones threaten the road. Most landslides occurred in the north side of the freeway in poor resistant limestone formations; the geological formation, trenching, and tilt have been the most important factors in these occurrences. The study of the position of active landslides on the route showed that the most dangerous parts of the freeway in terms of landslide risk are from km 1.5 to km 36 and from km 56 to km 62. Landslides either have not occurred in other parts of the roads or have only had non-threatening volumes. Prioritizing the risks of 21 active landslides, based on the considered factors, indicated that 11 landslides have the highest amount of risk, 3 are highly risky, and 7 are of a moderate risk. These landslides are mainly observed in two sectors of the route – the first part is from km 16 to km 36 and the second is from km 57 to km 60. According to the risk of landslides, the 104 km freeway is divided into 5 sections. The first section has a length of 1.5 km and is located in the area that has no risk. The second section has a length of 36 km and is in a dangerous area. The third section has a length of 19 km and is in an area that, in terms of being risky, ranges from slight to moderate. The forth section has a length of 6.5 km and is in a dangerous area. The fifth, and the last section has a length of 41 km and is located in an area of no risk. Thus, in terms of landslide risk, 42.5 km of the freeway is located in dangerous areas and 42.5 km of it is situated in areas that have no risk of landslide. The risk of rockfall in the freeway was also studied as another natural hazard to the road. Based on the field studies, 30 areas of active rockfalls were identified. Most of the active rockfalls have occurred in the north slopes with weathered, and mixed soil, bedrock and mainly in limestone formations combined with other stones. The identified rockfall areas are of high frequency of occurrence in two parts of the freeway. The first section is located in the distance between km 13 to km 20 of the freeway and includes 12 points of rockfall. In this section, rockfalls mainly consist of big rocks. The second part is located in the distance between km 23 to km 39 of the freeway and includes 12 points of rockfall. Rockfalls occur sporadically in other parts of the freeway. The prioritized areas of active rockfall, based on the hazard level, indicated that 6 points are of great danger, 18 points involve a high risk of rockfall, and 6 points are of medium risk level. Out of the 6 highly dangerous areas, 4 are located in the first part of the route (i.e. from km 30 to km 36), and the other two points are located in the second part of the freeway (i.e. from km 63 to km 93). The area of high risk of rockfall is located in the first part of the freeway (i.e. from km 13 to km 19.5) and in the second part of it (i.e. from km 25 to km 39). The areas with medium risk of rockfall are located in different parts of the road, especially at the beginning of the freeway. 4. Conclusion Based on the passive defense approach, the survey of Khorram abad-Pole Zal Freeway indicated that natural hazards such as landslides and rockfalls have a high frequency of occurrence in the area and that these phenomena are serious threats to the 104 km freeway as well as to structures such as tunnels, electric towers, etc. The study and mapping of landslides along the freeway indicated that the landslides are of more abundance and density in two specific sections of the route. The length of the route, considering active and dangerous landslides, is 42.5 km which includes 21 active landslide zones. Active areas of rockfall are also of serious threat to the freeway. The classification of the route into 7 different sections, based on the risk of rockfalls, showed that 3 sections involve no risk, 2 are of medium risk, and 2 are dangerous and highly risky. Accordingly, 17.2 km of the freeway is located in the risk-free zone, 63.1 km in the zone with moderate risk, and 27.3 km in the danger zone. Moreover, out of the 30 active areas of rockfall along the freeway, 6 points are highly dangerous, 18 have a high risk level, and 6 are of medium risk. Hence there are 24 active areas of rockfall that are of actual risk to the road. The results of the study showed that Khorram abad-Pole Zal Freeway is not in an acceptable condition from a passive defense point of view. The main reason for this is that the geological feature of the area have not been taken into account when designing the freeway. Natural hazards such as landslides and active rockfalls, due to overlooking the geological features of the area, have blocked, and destroyed, parts of the freeway and structures alongside it.}, keywords = {Freeway,Khorram abad-Pole Zal,Landslides,passive defense,Rockfall}, title_fa = {ارزیابی مخاطرات طبیعی آزادراه خرم‌آباد- پل زال با رویکرد پدافند غیرعامل}, abstract_fa = {آزادراه خرم‌آباد- پل زال به عنوان یکی از مهم‌ترین مسیرهای حمل‌ونقل جاده‌ای کشور، با طول 104 کیلومتر در استان لرستان واقع شده است. هدف از این تحقیق که از نوع تحقیقات کاربردی و روش آن توصیفی- تحلیلی و میدانی می‌باشد، بررسی مخاطرات طبیعی آزادراه خرم‌آباد- پل زال با رویکرد پدافند غیرعامل است. در این مطالعه از ابزارهای فیزیکی و مفهومی مانند نقشه‌های توپوگرافی 1:25000، زمین‌شناسی 1:100000، تصاویر ماهواره‌ای، GPS، فرم‌های برداشت اطلاعات میدانی و نرم‌افزارهایی مانند Arc GIS جهت تحلیل داده‌ها و نتیجه‌گیری استفاده شده است. نتایج حاصل از تحقیق نشان می‌دهد که رخداد خطر زمین‌لغزش و ریزش‌های فعال در مسیر مورد مطالعه مهم‌ترین تهدید برای مسیر و تأسیسات احداث شده در طول مسیر بوده و مهم‌ترین عامل در رخداد آن‌ها، ویژگی‌های سنگ‌شناسی است. بررسی و اولویت‌بندی آزادراه ازنظر مخاطرات ذکر شده حاکی از این است که 5/42 کیلومتر از مسیر در معرض زمین‌لغزش و 7/23 کیلومتر در معرض ریزش‌های خطرناک (فعال) قرار دارند؛ بنابراین مسیر آزادراه ازنظر مخاطرات طبیعی با رویکرد پدافند غیرعامل، دارای وضعیت مطلوبی نیست.}, keywords_fa = {زمین‌لغزش,ریزش,آزادراه,پدافند غیرعامل,خرم‌آباد- پل زال}, url = {https://geoeh.um.ac.ir/article_31345.html}, eprint = {https://geoeh.um.ac.ir/article_31345_7ba5faf581e4c1869ca2f2ec54f222d5.pdf} } @article { author = {Heidari, Mohammad Amin and Khoshaghlagh, Faramarz}, title = {Modeling the Relationship between teleconnection indexes with warm season temperature anomalies in Iran Using Multivariate Regression}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {47-66}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.57628}, abstract = {. Introduction Climatic variation is one of the inherent features of the climate system. The components of the climate system are diverse and complex, so that these components interact with each other in a Interweaving way, so that the change in each component eventually changes other components as well. The climate indicators are defined to describe the status of the climate system and its changes. Each climatic index describes some aspects of the climate based on certain parameters. Therefore, various climate indicators have been proposed and used in many studies. Climatic indices are measurable and computable and correlate with some of the elements of the climate in different regions. Some atmospheric variables such as pressure, temperature, precipitation and radiation, as well as non-atmospheric parameters such as sea surface temperature (SST) or ice cover, are among the factors to be considered for climate forcing in different parts of the world. The large water resources, such as seas and oceans, are among the most important climatic operators. These resources are capable of storing a large part of the solar energy and also, due to their fluid nature, are capable of transporting energy to other parts of the planet in various ways (surface flow, subsurface flow, convection, and moisture advection). Changes in ocean behavior, therefore, cause changes in atmospheric patterns, which can further change the short and long-term climatic conditions in different regions. For this reason, ocean surface temperature can be considered as one of the important indicators affecting climatic abnormalities. All patterns of teleconnection as natural phenomena's, are resulting from the turbulent nature of the atmosphere and its internal energy resources. These patterns represent macro-scale variations in atmospheric wave patterns and jetstream flows, and affect the distribution of temperature, precipitation, storm paths, and the status and pattern and speed of the jetstream in large areas. For this reason, the patterns of teleconnection lead to abnormalities that occur simultaneously in very distant areas (Asakere, 2007; 48). In fact, the variability of the behavior of the atmosphere is a result of the set of behaviors and interactions between the ocean and the atmosphere. Hence, indicators that explain the abnormal behaviors of the ocean and therefore the atmosphere can help to identify the causes and nature of the occurrence of short and long-term climate abnormalities in a region. The study of air temperature anomalies in the warm season in Iran in relation to the most important oceanographic and atmospheric indices is the main aim of this research. 2. Material and Methods In this study, two different databases were used including the data of the IRIMO stations and indexes data of oceanographic and atmospheric teleconnection of the NOAA Data Center, affiliated to the U.S. Center for Oceanography Studies. The data of the IRIMO stations consist of 30 synoptic stations with a period of 50 years of data (1961-2010). In the first step, the standardized temperature of each station was calculated per each month during the warm period of the year (from May to September). Then, for the purpose of detecting anomalies, a function was defined in Excel macro as; -0.5 >‌x> +0.5, and from among the 250 months examined the anomalies (at least 20 stations from 30 stations), 57 cases with anomalies among whole months were selected in the study period, and then by the Pearson correlation method, a relation was calculated between the 17 selected atmospheric‌-oceanic indicators and the air temperature. The indicators used in this study are the most important indicators introduced in international studies. Also, by using multivariate regression, optimal parameters and regression functions are presented in order to explain and predict the relationship between indices and temperature anomalies in the warm season in the whole of Iran. 3. Results and Discussion The air temperature of Iran shows a significant relationship with the teleconnection indexes. According to the tests performed in selective stations, in general, NINO3, NINO1‌+‌2, NINO3.4, NINO4, GBI, CAR, PACEFIC WARM POOL and GLOBAL MEAN TEMP indexes were have a significant correlation in 90% confidence level. In terms of time in calculations with monthly synchronous steps at selected stations, the best indexes are GBI, NINO1 + 2, NINO3 and NINO3.4, with correlations of 0.8, -0.8, -0.57 and -0.4, respectively. In terms of a previous step, the GBI, NINO1‌+‌2 and NINO3 indexes had the highest correlation values of 0.8, -0.8 and -0.5, respectively. The temporal pattern of the impact of some indicators, such as NINO, which was mostly strong and inversely in the same month, was directly and significantly in the two and three months earlier. Based on the results obtained from the multivariate modeling, the correlation between the selected teleconnection indexes such as GLOBAL MEAN TEMP, GBI, NINO 1‌‌+‌2 with thermal anomalies in the warm season of Iran are 0.94; as the best temperature predictions, and at the same time a month earlier, the NINO3 index was added to the above-‌mentioned indexes. In general, the indexes of NINO3-4, NINO3, NINO1‌+‌2, NINO4, and GBI are the best atmospheric and oceanographic indicators that predict Iran's temperature anomalies. 4. Conclusion According to numerical correlation analysis between the selective indexes and the temperature anomalies of the selective stations in the warm season in Iran showed that NINO3, NINO1 + 2, NINO3.4, NINO4, GBI and GLOBAL MEAN TEMPERATURE indexes are the most important oceanic-atmospheric predictors. Also, in this paper, linear regression functions for the relationship between indices and monthly temperature anomalies are presented, which can explain and predict the temperature changes in Iran. The correctness of these functions is confirmed by using the actual and modeled data (estimating R correlation values, RMSE and MBE values) with an acceptable error rate. It should be noted as long as the intervals of predicting are prolonged, apparently the importance of atmospheric indexes is reduced and contradictory the number and reliability of ocean indexes are increased. In total, using the above mentioned indices and using multivariate regression method in each step of time (simultaneously, one, two and three months earlier), the linear regression function for the relationship between indexes and monthly temperature anomalies of Iran has been presented, which by using it the Iran's temperature changes can be predicted finally. It should be noted that the functions obtained here are to predict the average temperature of selected stations in Iran, and therefore for each station the calculations must be made individually.}, keywords = {Climate Perdition,Modeling,Multivariate Regression,Temperature Anomaly,climatic teleonnetion Index,Iran}, title_fa = {مدل‌سازی ارتباط شاخص‌های پیوند از دور با ناهنجاری‌های دمایی فصل گرم در ایران با استفاده از وایازی چندمتغیره}, abstract_fa = {در رخداد ناهنجاری‌های آب‌وهوایی، نوسانات جوی و اقیانوسی جوی و اقیانوسی مؤثر هستند. یکی از انواع مهم این ناهنجاری‌ها دماهای ناهنجار و گرماهای کم سابقه به‌ویژه در فصل گرم سال است. برخی از چرخه‌های جوی و اقیانوسی در فزونی و تشدید ناهنجاری دما در این فصل مؤثر هستند. این پژوهش با هدف مدل‌سازی وایازی ارتباط مهم‌ترین شاخص‌های اقیانوسی و جوی با ناهنجاری‌های فراگیر دمای هوا در فصل گرم سال (ابتدای ماه مه تا انتهای ماه سپتامبر) در پهنه ایران انجام شده است. در این پژوهش رابطه همبستگی و توابع بهینه وایازی بین 17 شاخص جوی و اقیانوسی و مقادیر استاندارد شده دما در 30 ایستگاه همدید کشور با دوره آماری بیش از 50 سال داده (1961-2010) و با روش پیرسون و در چهارگام زمانی متفاوت (به ترتیب گام همزمان، یک، دو و سه ماه پیشتر) به‌منظور تبیین و پیش‌بینی ناهنجاری دمای هوا در ایران ارائه شده است. بر این اساس تحلیل همبستگی عددی بین شاخص‌های مورد بررسی و ناهنجاری دمایی ایستگاه‌ها در فصل گرم سال در پهنه ایران نشان داد، شاخص‌های NINO3، NINO1+2، NINO3.4، NINO4، GBI، GLOBAL MEAN TEMPERATURE، از مهم‌ترین شاخص‌های اقیانوسی-جوی مرتبط با ناهنجاری دمایی فصل گرم در منطقه مورد مطالعه هستند. همچنین در این پژوهش توابع وایازی خطی برای ارتباط شاخص‌ها و ناهنجاری ماهانه و متوسط دمای ایران ارائه گردیده، که به‌وسیله آن می‌توان تغییرات دمایی ایران را تبیین و پیش‌بینی کرد. صحت عملکرد این توابع با استفاده از مطابقت داده‌های واقعی و مدل‌سازی شده (برآورد مقادیر r همبستگی، مقدار RMSE وMBE) با میزان اریبی قابل قبولی مورد تأیید قرار گرفته است.}, keywords_fa = {مدل‌سازی آماری,وایازی چندمتغیره,ناهنجاری دما,شاخص‌های پیوند از دور,ایران}, url = {https://geoeh.um.ac.ir/article_31377.html}, eprint = {https://geoeh.um.ac.ir/article_31377_abd301e4766f5260cc34ddc0a6ba1000.pdf} } @article { author = {Behyan Motlagh, Sodabeh and Pajoohesh, Mehdi and Abdollahi, Khodayar}, title = {Assessing the Effect of Watershed Spatial Characteristics on Regional Calibration for a Single Event Flood Model: The Case of Kohsukhteh Catchment}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {67-83}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.58862}, abstract = {1. Introduction Application of hydrological models is one of the common methods for quantitative analysis of watersheds. A class of these models is used to simulate rainfall-runoff processes. A hydrological rainfall-runoff model deals with integration of time series data, operational parameters, local variables and physical governing system laws in order to simulate runoff and other processes of the catchment. The flood hydrograph is an important graphical representation in hydrological analysis. The shape of hydrograph is a direct response to management strategies basin. In fact, watershed management is not possible unless hydrological characteristics of the basin could be fully understood. HEC-HMS model is a rainfall - runoff model with either a simple lump or a quasi-distributed structure. The model was developed by Hydrologic Engineering Center of US Army Corps of Engineers. One important capability of this model is the possibility of its integration with ArcGIS. The HEC-GEOHMS extension automatically calculates most of the geospatial data that needs to be calculated manually. Its user-friendly interface offers several tools/icons such as the basin, reach, junction, etc. to enter the data. The component-based set up of the model makes it possible to modify the structure of the modeling system by the user. Different options for calculating the loss method, transmission, and streaming flow are available in HEC-HMS model. Each element has its own parameters or inputs. This flexible system provides an opportunity to apply the model to the regions with limited access to data. For a similar reason, models like HEC-HMS are useful tools to investigate the effects of changes in some of the spatial and temporal variables. In this study, the effects of the spatial scale on the optimization of HEC-HMS have been investigated. The modeling parameter sets obtained by large scale setting generally outperform local scale hydrologic parameterization. Most research in the field of calibration of hydrological models has focused on the local parameters but if the at larger scales, it can be regionalized to other places. In such procedures, the sensitivity analysis is initially used to identify the most important parameters. The aim of this study was to compare local and large scale calibration. 2. Material and Methods Kohsukhteh watershed is geographically located between 50 °40' to 51 ° 20 ' East longitude and 31° 20' North and 32 ° latitude. The study area covers an area of 2783 square kilometers. The minimum and maximum elevation values in this basin are 1705 and 3398 meters respectively. The average slope of the area is 19%. The mean recorded annual precipitation (Shahrekord synoptic station) is 320 mm. Data preparation for HEC-GEOHMS was the first stage of modeling. Different physical characteristics, base maps and time series data of the basin were introduced to the model. The model set up was implemented by setting Loss, Transform and Base-flow methods for each sub-basin. The necessary steps for meteorological model and control specifications were taken as well. The 6-hour rainfall and 6-hour discharge time series were primarily used for the analyses. The model was parameterized at both local and large scale levels. Parameters related to Loss method, Transfer method and Routing were selected on the basis of model performance. In order to identify the most sensitive parameters, sensitivity analysis was performed. Given that the accuracy of the input parameters is an indicator of the efficiency of modeling and the results of the final simulation, the results depend on this stage. After identifying the sensitive parameters, they were selected to optimize the model locally and in a large scale. Despite the uncertainties and errors of the models, no computer model can expect a complete and accurate prediction. Therefore, they should be calibrated and validated. To evaluate the performance of models with different conditions, six events were chosen for the calibration and two for validation of the model. 3. Results and Discussion Sensitivity analysis on the parameters of the model showed that Lag time parameter and initial abstraction had the highest sensitivity. Calibrated values of the model parameters were obtained for both calibration and validation events. The results of calibration in six events and the observed and simulated runoff volume in the basin were compared. Two events were selected to validate the calibrated model. Runoff discharge and volume for the basin were simulated. The values obtained by simulation were compared against the recorded observational data at the hydrometric stations were compared. After calibration and optimization of the model at local scale, the results showed that both estimated peak discharge and the time to peak flow, was performed better than obtained values for the basin scale simulation. The inter-comparison among the events also show some differences in model performance. Event December 25, 2012 showed the highest accuracy and March 30, 2012 was simulated with the least accuracy. The difference may be due to the change in soil permeability during winter time. In the case of large scale model, the Event December 25, 2012 was simulated with high efficiency. Lag time, initial abstraction, curve number and impervious ratio were identified as the most important factors for calibration. The obtained Nash-Sutcliffe for local calibration was 0.85 while it dropped to 0.65 for large scale calibration. 4. Conclusion Modeling is an indirect method that is much faster than field methods. In order to achieve accurate results in modeling, we need to estimate the model parameters as well as the time and place of variables. Calibration refers to the process of comparing of the measurements against the estimated values. The use of local scale calibration versus large scale calibration has a higher apparent accuracy, and this is in line with Samaniego, Kumar and Attinger (2010) and Hundecha and Bárdossy. (2004). However, the commutated value for Sutcliffe model efficiency is less variable in the case of local calibration. It was demonstrated that the simulated peak runoff was closer to observations in local calibration compared to the large scale calibration. A similar result was found with the simulated runoff volume using local calibration. Although, both calibration settings provided an acceptable response to the estimation of runoff; the obtained parameters at basin scale show less spatial sensitivities. This makes it possible to generalize the calibration results to nearby areas with limited data. The results show that the large-scale parameterization actually has less spatial dependency and therefore may provide more reliable results. This finding is in line with reported advantages of large-scale parameter estimations, in term of saving the time (Troy, 2008; Pokhrel, 2008; Beven, 2001). Sensitivity analysis also showed that parameters such as imperviousness and initial abstraction had a high sensitivity in the study area.}, keywords = {Global-scale optimization,Hydrological modeling,Local-scale optimization,SCS}, title_fa = {بررسی اثر خصوصیات مکانی حوزه آبخیز بر واسنجی وقایع تک رخدادی سیلاب (مطالعه موردی: حوضه آبخیز کوه سوخته)}, abstract_fa = {استفاده از مدل‌های هیدرولوژیکی یکی از روش‌های رایج در تجزیه‌وتحلیل کمی حوضه‌های آبخیز است. پیشرفت‌های اخیر در زمینه‌سازی‌‌های بارش –رواناب که انعطاف بیشتری در حل مسائل و پدیده‌های هیدرولوژیکی دارند، آن‌ها را جایگزین مناسبی به‌جای روابط تجربی کرده است. به‌طور مرسوم در پژوهش‌های صورت گرفته پیشین مبتنی بر بهینه‌سازی مدل در همان مقیاس محلی موردبررسی قرارگرفته که فاقد عمومیت مکانی است. هدف این مطالعه ارائه پارامترهایی با اندازه معین است تا در سطح عمومی‌تری برای تمام زیرحوضه‌ها پاسخ قابل قبولی را ارائه دهد. بدین منظور پارامترهایی از مدل هیدرو گراف سیلاب که در هیدروگراف سیلاب نقش دارند، در مقیاس زیرحوضه‌ای و بزرگ‌مقیاس مورد مقایسه قرارگرفته است. در این مطالعه از مدلHEC-HMSبرای مدل‌سازی رواناب زیر حوضه‌ها و میزان رواناب خروجی از حوضه استفاده‌شده است؛ برای ساختار مدل از عوامل شماره منحنی SCS برای روش تلفات و هیدروگراف واحد SCS جهت روش انتقال استفاده شد. به‌منظور واسنجی ابتدا بهینه‌سازی پارامترها در هریک از زیرحوضه‌‌ها به‌صورت جداگانه انجام گرفت و سپس مقدار عمومی پارامترها با به دست آوردن اندازه ثابتی از پارامترهای حساس که در همه زیر حوضه‌ها پاسخ قابل قبولی ارائه دهند، انجام شد. یافته‌های تحقیق نشان می‌دهد که گرچه کارایی مدل در واسنجی با پارامترهای محلی برتر از واسنجی با استفاده از پارامترهای بزرگ‌مقیاس است، ولی ایستایی پارامترهای عمومی بهتر است. به‌منظور ارزیابی کارایی مدل از شاخص Nash-sutcliffeاستفاده گردید که این شاخص برای کالیبراسیون محلی 85/0 و کالیبراسیون بزرگ‌مقیاس 65/0 به دست آمد که در دامنه مطلوبی برای شبیه‌سازی قرار دارد.}, keywords_fa = {مقیاس محلی,بزرگ‌مقیاس,مدل هیدرولوژیکی,HEC-HMS,SCS}, url = {https://geoeh.um.ac.ir/article_31408.html}, eprint = {https://geoeh.um.ac.ir/article_31408_18a0b46a5190d1c56a3eee90300c2f6b.pdf} } @article { author = {Hemmati, Fariba and Mokhtari, Davoud and Roostaei, Shahram and Zamani Gharechamani, Behzad}, title = {Zoning Tectonic Activities of Banarovan Using Morphotectonic Indices}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {85-107}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i2.59240}, abstract = {1. Introduction There is almost no region in the world that has not undergone tectonic changes during the recent millennia (Keller & Pinter, 2001). For this reason, evaluation and investigation of active tectonic processes and their effects, for example earthquakes, are of vital importance for many human activities including the design and construction of cities, power plants, and dams as it helps minimize their risks and damages (Soleymani, 1999). The Benaravan fault, located on the east of a mountain, is part of the Mianeh-Ardebil fault. The 20 km long Benarvan fault is one of the most significant ones in the region. It is located on the southern skirt of Azerbaijan’s Mount Bozgush and extends in the southwest-northeastern direction. Its route features special attributes concerning domain instabilities and geomorphological phenomena (Monroe & Wicander, 2001). Tectonic and geomorphic activities, relatively low-resistance lithology (Miocene era degenerative sediments), intense faulting of the region and being located in the very high risk region of earthquake (Benarvan fault and adjacent faults), and the high level of subterranean waters result in the possibility of natural risks such as earthquake and other types of mass movement. The significance of such a research is due to the location of numerous residential areas across the Benavran fault. So far, there have been many studies on the behavior of faults based on morphotectonic indicators in Iran and the world, the results of which indicate the potential of these indicators in analyzing the behavior of faults. 2. Material and Methods In this research, the basin was divided into sub-basins initially in order to ease calculations and outcome comparisons. Then, using quantitative indicators, the researchers investigated the effects of tectonic activities on the valleys and riverbeds. The bulk of the data needed for indicators was acquired from 1:25000 scale topographic maps, especially digital and aerial maps (Keller & Pinter, 2002). The morphological indicators used for the region are the following: hypsometric curves and integrals, asymmetry index of the drainage area (asymmetry factor), symmetry factor of the transverse topography, stream length gradient index (SL), valley width to height ratio (VF), the V ratio, and drainage basin shape ratio (BS). After calculating the geomorphic indicators of the studied area, the researchers estimated the tectonic activities using the IAT index. The IAT index is obtained from the mean value of different geomorphic indicator classes. 3. Results and Discussion In this research, the waterways and the basin border were marked using a 1:25000 and 1:100000 scale geologic maps, respectively. 3.1. The hypsometric curve and integral Eight hypsometric curves were produced for the studied basin. According to the curves for sub-basins, sub-basins 1 and 2 had an under-curve area of above 50%, being relatively convex. This indicated the young age of the basin. Moreover, the convex form of the dimensionless curve indicated the prevailing of neo-tectonic activities over eroding ones. 3.2. Calculating the asymmetry index of the basin. The asymmetry index was higher in basins 2, 5 and 6, and lower than 50 in 1, 3, 4, 7 and 8, which points out their deviation. The T index indicated the semi-asymmetric form of the majority of sub-basins that fall into class 2 regarding their tectonic activities. The river gradient index was one of the significant indicators for differentiating between active and non-active tectonic areas. The mean stream length gradient index or SL for the basins varied from 482 for basin 2 to 71 for basin 6. The VF index showed that the bulk of the basin is within the active area; indicating that tectonic activities have not given the stream sufficient opportunity for erosion. The basin shape index for each case indicated that basins 2 and 7 are active and elongated, while the rest are inactive and fall into class 3. 3.3. Relative evaluation of regional tectonic activates according to geomorphic indicators (IAT) In this study, eight morphotectonic indicators were calculated for each of the 8 basins, dividing them into 3 geomorphic levels. Then, the values for geomorphic index (S/n) were measured discretely for each basin; being classified into 4 levels, i.e. the index of relative active tectonics (IAT) of the study’s expanse. The classification for geomorphic indicators proposed by Hamdoni, Irigaray, Fernandez, Chancon & Keller (2008) classified these indicators based on the quantitative value into 4 classes. The class quantities of all indicators were combined, and their mean values were presented as the IAT index, indicating the tectonic activity. According to the results obtained from the IAT index, there is very strong tectonic activity in basin 2, with strong, moderate and weak tectonic activation witnessed in the remaining basins. The results of evaluation showed that the basins’ tectonic activities range from very strong to strong, moderate and weak. 4. Conclusion Quantitative measurement allows geomorphologists to compare different landforms in a factual, rational manner, subsequently calculating morphologic indices. Regarding the hypsometric curve and integral for sub-basins 1 and 2, the under-curve area was above 50%, indicating its young age. Also, the convexity of dimensionless curves indicated the prevalance of neo-tectonic activities over eroding ones. For sub-basins 3 to 8, the under-curve area was below 50%, resulting in a more concave hypsometric curve that indicated eroding activities in these sub-basins. Concavity in the dimensionless curve indicated the dominance of eroding activities over neo-tectonic ones. 4.1. The asymmetry index of the drainage basin In basins 2, 5 and 6, this index was above 50, while for basins 1, 3, 4, 7 and 8, it was below 50. This indicated the deviation of basins. The topographic symmetry index indicated that the majority of basins are semi-symmetric, falling into class 2 regarding their tectonic activities. In the studied region, the SL index for the main waterways of 8 sub-basins was measured. The mean value of the gradient index or SL for the basins varied from 482 for basin 2 to 71 for basin 6. According to the valley width to height index, the bulk of the basin is within the active region. This indicated that tectonic activities have not given the regional stream sufficient opportunity for erosion. The V ration index, called the valley morphology index, was obtained via comparing the transverse area of the actual valley to the area of a hypothetical semicircle with a radius equal to the valley depth. In sub-basin 7, it indicated the existence of a valley with larger width and less depth, the type which incurs higher erosion. The basin shape index indicated that basins 2 and 8 are active and elongated, while the rest are inactive and fall into class 3. The IAT index classified the tectonic activities of the region in the three classes of very strong, strong and moderate. According to this index, there is no basin with weak activities in the region. According to the segmentation map, the highest activity occurred in sub-basin 2, and the least in sub-basins 3, 4 and 7. The study and evaluation of different geomorphic indicators of the region show that it is young and active regarding neo-tectonic activities, yet this activity is not equal in all sectors. In sub-basin 2, young activities were the highest. This could be attributed to the stronger activity of the major and minor faults, resulting in the rise of the area.}, keywords = {Benarvan fault,Neo-tectonic evaluation,Morphological indicators}, title_fa = {ارزیابی فعالیت‌های نئوتکتونیکی محدوده گسل بناروان بر اساس شاخصه‌های ریخت‌سنجی}, abstract_fa = {رشته‌کوه بزغوش در شمال‌غرب ایران و بین استان آذربایجان شرقی و اردبیل با روند شرقی- غربی در مختصات بین َ 00 °48 تا َ 30 °47 درجه طول شرقی و َ 00 °38 تا َ 30 °37 درجه عرض شمالی قرار دارد. در این پژوهش رفتار گسل بناروان مورد بررسی قرار می‌گیرد و هدف از این پژوهش درک بهتری از رفتار تکتونیکی گسل، بررسی اثرات تکتونیک در تکامل چشم‌انداز و تجزیه‌وتحلیل مورفولوژی است. به‌منظور به دست آوردن اطلاعات بیشتر در مورد فعالیت نئوتکتونیک، ویژگی‌های ژئومورفولوژیکی فعالیت گسل بر اساس ارزیابی سیستم زهکشی رودخانه، ژئومورفولوژی پرتگاه‌ها و جبهه‌های کوهستان بر اساس روش‌های ارزیابی حرکات تکتونیکی فعال مورد مطالعه قرار گرفته است. در این مطالعه با استفاده از شاخص Iat، ارزیابی نسبی فعالیت‌های تکتونیکی در محدوده گسل بناروان در دامنه جنوبی رشته‌کوه بزغوش انجام شد. برای برآورد شاخص Iat، هفت شاخص ژئومورفیک شامل: منحنی‌های هیپسومتری و انتگرال هیپسومتری (Hi)، شاخص عدم تقارن حوضه زهکشی (فاکتور عدم تقارن)(AF)، فاکتور تقارن توپوگرافی عرضی (T)، شاخص طول جریان رود به شیب رود (SL)، نسبت پهنای کف دره به ارتفاع (VF)، شاخص نسبت (V) و نسبت شکل حوضه زهکشی (BS) محاسبه شد. شاخص Iat، فعالیت‌های تکتونیکی منطقه را در سه کلاس، فعالیت‌های بسیار زیاد، زیاد و متوسط طبقه‌بندی کرد. بر اساس این شاخص در منطقه، حوضه‌ای که دارای فعالیت‌های کم باشد، وجود ندارد. با توجه به نقشه پهنه‌بندی فعال‌ترین منطقه زیر حوضه 2 و کمترین فعالیت در زیر حوضه‌های شماره 3، 4 و 7 مشاهده می‌شود. مطالعه و ارزیابی شاخص‌های مختلف ژئومورفیک در منطقه مورد مطالعه بر روی 8 زیر حوضه در منطقه مورد مطالعه نشان می‌دهد که منطقه از لحاظ فعالیت‌های نئوتکتونیکی با تکتونیک جوان فعال می‌باشد؛ منتهی میزان فعالیت در همه جای آن یکسان نیست. در زیر حوضه شماره 2 فعالیت‌های جوان بیشتر از سایر زیر حوضه‌هاست. علت آن را می‌توان به فعالیت بیشتر گسل اصلی و گسل‌های فرعی که موجب بالاآمدگی منطقه شده است، نسبت داد.}, keywords_fa = {ارزیابی نئوتکتونیکی,شاخصه‌های ریخت‌سنجی,گسل بناروان}, url = {https://geoeh.um.ac.ir/article_31502.html}, eprint = {https://geoeh.um.ac.ir/article_31502_22b6ad24322e5358ec4aae4ed1d58e9f.pdf} } @article { author = {Asakereh, Hossein and ShahbaeeKotenaee, Ali}, title = {Synoptic Analysis of Productive Patterns of Winter Cold Wave’s in Iran}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {109-124}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.59919}, abstract = {1. Introduction One of the special temperature states in which extreme amounts of minimum temperature are observed, is the cold wave. The extreme cold waves due to the severity and sudden occurrence have an important impact on the ecosystems and human societies. There is a probability of occurrence of cold waves throughout the year and in each season, it creates its own special problems and damages. Because of the low angle of sunshine and the cold weather, these waves are stronger in winter and threaten the life of all living creatures. They also play a decisive role in economic, environmental and developmental issues such as road construction, damping and bridge construction, and can cause damage in various sectors. The intensity and weakness of the cold waves depend on the complex synoptic and dynamics factors, some of which are less well-known and their analysis using a synoptic method can identify features such as the source, track, intensity and frequency of pressure systems and helps to recognize the fundamental factors and their characteristics and to increase our understanding of winter cold waves. 2. Material and Methods The study area in this research includes the whole country of Iran. Iran is a rugged country with an elevation average of about 1250 meters. roughness plays an important role in Iran's temperature; therefore, the temperature decreases wherever height increases. Iran’s average maximum temperature is 18 degrees Celsius and the average minimum temperature is 11 degrees Celsius. In the present study, the effective patterns in creating winter cold waves in Iran were identified using environmental to circulation approach. In order to achieve the specified purpose in this study, two environmental and atmospheric databases were used. Environmental data included the minimum temperature in winter between 1960 and 2011. In this research, it has been attempted to be defined the cold Somehow so that the principle of its relativity is considered in different regions; accordingly and according to Alijani and Hooshyar (2008) and Massoudian (2013) researches, Two conditions for the identification of cold waves were defined in the country. On the basis of the first condition, days were considered as a day with a cold wave that standard Z score for the 10th percentile of minimum temperature data is less than or equal to -1/2. By defining this condition, only very low temperatures were taken into consideration for each of the 7187 cells studied and the concept of relative coldness was considered for different regions of the country. The second condition is the continuity of the cold weather for at least 3 days; based on this condition, the systemic coldness from the local coldness (which is caused by environmental factors or overnight cooling) is separated. According to these conditions, cold days were identified on the ground and related synoptic systems were investigated in different layers of the atmosphere. 3. Results and Discussion In the first pattern, about 45 percent of the country's surface was affected by the cold wave, and the average minimum temperature was -4.4 Celsius degrees. Based on surface temperature maps in the northwestern part of the country, temperatures below -20 ° C was observed. The main factor behind the formation of this pattern is the Azores high pressure system, which has led to cold weather penetration from northern Europe to Iran. Due to the formation of the second pattern, about 21 percent of the Iran’s surface was affected by the cold wave. The average minimum temperature in the country is -2.9 Celsius degrees, which was the highest among other patterns. The lowest temperatures in this pattern were between -14 and -18 Celsius degrees that observed in the northwest, the central parts of the Alborz and northeast of the country. In the third pattern, the daily average of minimum temperature is -2.5 Celsius degrees, which is the lowest at the different patterns. In this pattern, 50 percent of the country's surface was affected by the cold wave. In this pattern, cold weather penetrates the southern parts of the country and its impact was observed in many parts of the country. On the day the representative, the Siberian high-pressure system is located at high latitudes and in the central parts of Russia. The weakening of the Iceland low-pressure and the displacement Azores high-pressure towards the westerner parts, has strengthened the Siberian high-pressure and increased its impact. The minimum temperature average in the fourth pattern was -3.5 Celsius degrees and the cold air coverage in the country was 30 percent. Lowest temperature values were observed in northern parts of the provinces of East Azerbaijan and Ardabil. This pattern is somewhat similar to the first pattern, but contrary to the first pattern, there is a negative pressure anomaly in the northern regions of Europe and throughout Russia. The Siberian high pressure has shifted to the east and the European high pressure is located throughout the region, while in the first pattern, this high pressure was located in Western Europe. The minimum temperature average in the Fifth pattern was -3.4 Celsius degrees and the cold weather coverage in the country was 36 percent. In this pattern, the core of the Siberian high-pressure is located in west of Mongolia, and the Icelandic low-pressure was eastward movement and located in Scandinavia. This system has been located in large parts of northern Europe and central Russia as well as parts of the Atlantic in Western Europe. The expansion of this system and its displacement have caused more impact on Siberian high-pressure. 4. Conclusion Performing synoptic analyzes on atmospheric patterns showed that all the pervasive cold waves in Iran were caused by the formation of massive high-pressure patterns in the country, parts of the Middle East and Asia and South-East Europe. The position of the two Siberian and Azores high-pressure systems has played a very important role in the transfer of cold air to the northern latitudes towards the country. The deployment of a polar low-pressure system in northern parts of Europe and Russia has led to the influx of cold air towards the southern regions. The formation of specific patterns of the intermediate layers of the atmosphere has had a significant effect on the creation and intensification of the winter cold waves. So that the extreme winter cold waves are formed when Blocking systems have been established in Eastern Europe and their eastern Trough has been located on Iran.}, keywords = {comprehensive Cold wave,Cluster analysis,Synoptic climatology,blocking system,Iran}, title_fa = {تحلیل همدید الگوهای جوّی توأم با موج‌های سرمای زمستانه در ایران}, abstract_fa = {در پژوهش حاضر تلاش شده با استفاده از رویکرد محیطی به گردشی، الگوهای همدید توأم با موج‌های سرمای زمستانی در ایران شناسایی شود. براین اساس با استفاده از داده‌های میان‌یابی شدۀ دمای کمینه برای زمستان‌های 1339 تا 1388 ضمن شناسایی روزهای همراه با سرمای فراگیر، داده‌های جوی شامل فشار تراز دریا و ارتفاع ژئوپتانسیل تراز 500 هکتوپاسکال برای شناسایی الگوهای جوی همراه با موج-های سرمای فراگیر زمستانه در ایران بکار گرفته شد. با انجام تحلیل خوشه‌ای بر روی داده‌های فشار تراز دریا طی 487 روز همراه با سرمای فراگیر، درنهایت 5 الگوی همدید تشخیص داده شد. بررسی این الگوها نشان داد که تمامی موج‌های سرمای فراگیر در پهنۀ کشور با تکوین یک الگوی پرفشار گسترده بر روی ایران و مناطق همجوار آن توأم بوده است. برهمکنش سامانه‌های پرفشار سیبری و پرفشارهای اروپایی با کم‌فشارهای جنب قطبی در انتقال هوای سرد از نواحی قطبی و شمال اسکاندیناوی به عرض-های جنوبی نقش مهمی داشته است. همچنین استقرار پشته‌ها و سامانه‌های بندالی تراز میانی جو در بخش‌های مرکزی و شرقی اروپا و استقرار ناوۀ شرقی آن‌ها بر روی ایران با ریزش هوای سرد به قسمت عقب این ناوه توأم بوده و در ایجاد و تداوم موج‌های سرمایی در سطح کشور تأثیر زیادی داشته است.}, keywords_fa = {موج سرمای فراگیر,تحلیل خوشه‌ای,اقلیم‌شناسی همدید,سامانۀ بندالی,ایران}, url = {https://geoeh.um.ac.ir/article_31521.html}, eprint = {https://geoeh.um.ac.ir/article_31521_8384a6f4729c91e540a2ba4ba3169f48.pdf} } @article { author = {Heshmati, Mosayeb and Gheitouri, Mohammad and Sheikhvaisi, Morad and Arabkhedri, Mahmood and Hosini, Majid}, title = {Combating the Forest Mortality Crises in Zagros Regions, Iran through Adaptive Approaches Solutions}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {125-141}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i2.60466}, abstract = {1. Introduction Zagros forests (Quercus sp.) contribute to recharging groundwater, controlling air pollution, ecotourism, by products, livestock grazing, sustaining agriculture, soil conservation and flood control. Due to geological and topographical properties of Zagros area, however, these forests are more vulnerable to deforestation agents mainly drought driven die-off phenomenon. The effects of climate change are generally expected to reduce the growth and survival of forests, which not only predisposes them to being disturbed by insects and disease, but also increases the vulnerable ones to higher tree mortality. As a consequence of continued climate change, forest mortality has spread throughout Zagros areas inducing a severe environmental disaster. According to some research, several biotic and abiotic factors, such as extreme weather conditions, drought, storms, heat, and insect fluctuations, are responsible for oak reduction. Regarding rainfall deficit, soil moisture storage and reduction in evapotranspiration should be considered as the possible solutions through short term measures. Consequently, harvesting runoff by micro-catchment construction such as crescent -shaped bund (CSB) is a possible adapted measure in the semiarid regions for enhancement of soil moisture. In order to evaluate the effects of runoff harvesting on forest rehabilitation, the present research aimed to analyze the effects of CSB on soil soil moisture content. 2. Material and Methods This study was conducted in Kalehzard site located in Kermanshah, west of Iran (UTM; 38S682887E, 3748385N). The respective annual precipitation and temperature are 440 mm and 15.2 ºC, indicating the semiarid region. The winter is so cold that the temperature drops below zero on average for 90 days during December, January and February. The summer is relatively hot and dry. A hill with a 15% slope and south-eastern aspect was chosen as the experimental site to represent the dieback phenomenon in Zagros forests. The experiment was a randomized complete block design with four treatments and three replications. The experiment was conducted as a randomized complete block design with four treatments including crescent shaped bund with preservation (CSB+P), preservation treatment (PT), crescent shaped bund without preservation (CSB-P) and control treatment (CT). CSB+P was constructed to assist reduction in dieback rate and even re-vegetation of some dried forest trees through its effects on harvesting runoff. This technique is perpendicularly in the slope direction with the opening perpendicular to the flow of runoff, capturing runoff inside. The frequency of both dieback and healthy trees was recorded twice a year, therefore, the total number of trees was recorded before the construction of bunds within the plots using 100% inventory method. Soil quality, soil moisture and plant canopy were analyzed within treatments and repeated every year during the research period. 3. Results and Discussion Results explored that the effects of CSB+P treatment on reduction of dieback rate and re-growing of some dried trees was 36.7 and 19 tree ha-1 respectively (totally 55.7 ha-1 tree in the forest stand). Therefore, both the reduction of mortality rate and re-growing of dried trees are two main positive effects demonstrated by CSB+P measure. PT treatment has no effect on re-growing, while it contributes to the reduction of dieback severity (37.7 tree ha-1). Finally, CSB-P was found the lower level on dieback reduction was 6 tree ha-1, revealing the crucial importance of preservation for the protection of built bund. As a result, micro-catchment and preservation have a significant positive effect on forest restoration through soil moisture retention. Results also showed that the respective means SOC in the CSB+P, PT, CSP-P and CT treatments were 2.35, 2.40, 1.90 and 1.80 %, indicating no significant difference among them. However, the means significantly (p>0.05) increased in the CSB+P and P treatments over time. CSB+P significantly reduced bulk density from 1.46 (1st yr) to 1.32 (3rd yr) enhancing soil moisture content. The crescent shaped bund was designed as the adaptive micro-catchment runoff harvesting system (MCRHS) and measured within treatments plots. This technique has a lower soil and embankment movement than earthy or stone dams which can be built perpendicularly in the flow of runoff. Besides, it is arranged in staggered rows along the natural contour of the land with the open end facing uphill. Consequently, these bunds slow down runoff enabling the harvested water to be used in an effective way. This is particularly useful in increasing the soil moisture, especially when precipitation is scarce. 4. Conclusion It is concluded that CSB+P (first treatment) can be considered as the possible adaptation approach for combating Zagros forest mortality induced by drought stress and climate change. This technique is a possible measure for runoff harvesting and thereby enhancement of soil moisture during dry season. However, proper and holistic management of forests are needed to curtail forest dieback event. Furthermore, Zagros forest soil should be protected from disturbance factors in terms of tillage practice, machinery traffic, grazing, logging and charcoal extraction. In our experience, runoff harvesting through micro-catchment technique, forest preservation and sustaining SOC are crucial short term measures for combating forest mortality in Zagros regions.}, keywords = {Adaptation approaches,Crescent bund,Oak dieback,Soil Moisture}, title_fa = {مقابله با خشکیدگی جنگل‏های زاگرس با رویکردهای جمع آوری آب باران و حفظ رطوبت خاک به‏منظور مدیریت پیامدهای محیط زیستی آن}, abstract_fa = {جنگل‌های بلوط زاگرس نقش ارزنده‏ای در تغذیه آب‌های زیر زمینی، پایداری کشاورزی، حفاظت خاک و کنترل سیل دارند. بااین‌وجود، تغییرات اقلیمی از جمله کاهش بارش موجب خشکیدگی بخش قابل توجهی از این منابع ارزشمند شده است. هدف از اجرای این تحقیق یافتن رویکردهای مناسب سازگاری با تغییرات اقلیمی به‏منظور کاهش شدت خشکیدگی درختان جنگلی از طریق استحصال آب باران و ذخیره آن در خاک بود که در بخشی از جنگل‏های استان کرمانشاه در قالب طرح آزمایشی بلوک‌های کامل تصادفی انجام یافت. تیمارهای مورد آزمایش شامل بانکت+قرق، قرق، بانکت بدون قرق و شاهد با سه تکرار بودند. بانکت‏ها به‌طور منقطع و هلالی شکل به‏طول 7 متر و فاصله تقریبی چهار متر به شکل زیگزاکی ایجاد شدند. نتایج این تحقیق نشان داد که اعمال تیمار بانکت+قرق بعد از سه سال، موجب کاهش خشکیدگی 37 پایه و احیای 19 پایه در هکتار (در مقایسه با تیمار شاهد) گردید (درمجموع 57 پایه). تیمار قرق گرچه موجب احیای پایه‏های خشکیده نگردید، اما موجب کاهش تشدید خشکیدگی به تعداد 38 پایه در هکتار گردید. تأثیر تیمار بانکت بدون قرق منجر به کاهش خشکیدگی به تعداد شش پایه در هکتار به دلیل عدم حفاظت و چرای دام شد. نهایتاً افزایش معنی‏دار کربن آلی خاک و بهبود جرم مخصوص ظاهری نیز بر اثر اعمال تیمارهای بانکت و قرق به دست آمد که به‌نوبه خود منجر به افزایش ظرفیت ذخیره رطوبت خاک شدند. بر اساس نتایج این تحقیق، فائق آمدن بر خشکیدگی جنگل‏های زاگرس مستلزم مدیریت مستقیم و جامع جنگل‏ها با رویکردهایی مبتنی بر سازگاری با شرایط خشکسالی و حذف عوامل تخریب، به‌ویژه عوامل برهم زدن نیمرخ خاک مانند شخم و کاربرد ماشین‏آلات سنگین در عرصه‏های جنگلی است. اساس این رویکردها حفظ رطوبت خاک، سازگاری با شرایط خشکسالی، حذف عوامل تشدید خشکیدگی درختان جنگلی و تداوم پژوهش‌های بیشتر است.}, keywords_fa = {بانکت های هلالی,خشکیدگی بلوط,رویکردهای سازگاری,رطوبت خاک}, url = {https://geoeh.um.ac.ir/article_31568.html}, eprint = {https://geoeh.um.ac.ir/article_31568_cb11d7e5c3c8831d38030ccc5e29cb97.pdf} } @article { author = {Mafakheri, Omid and Saligheh, Mohammad and Alijani, Bohlool and Akbari, Mehri}, title = {The Hazards of Rainfall Concentration in Iran}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {143-162}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.60987}, abstract = {1. Introduction Since the spatial and temporal distribution of rainfall in Iran is influenced by the distribution of global circulation systems, the lowest change in its pattern is resulted in the severe weather abnormalities. Therefore, spatial and temporal abnormalities of rainfall, severe changes in rainfall intensity, and rainfall difference are the main characteristics of Iran's rainfall. Worthy studies have been carried out in relation to the temporal and spatial variations of rainfall, as a result, their conclusion showed that the number of precipitation is lower but the severity is higher. The purpose of this study was to investigate and identify changes in the number of rainy days, average daily precipitation, rainfall variation changes and the resulting hazards in the long-term statistical period. 2. Material and methods First, daily precipitation data of 53 synoptic stations with a common statistical period from 1984 to 2013 were received from the Meteorological Organization. Then, they were selected to determine the rainy day (precipitation at 0.1mm and above). From the viewpoint of precipitation duration, 7 classes were identified. 1 day precipitation, precipitation with two-day sequence, and precipitation with a sequence of 3 to 7 days of rainfall were extracted. Cluster analysis was used to identify climatic regions and their features. The final result was the division of the country into seven regions with the highest intra-group similarity and the most difference among groups in terms of the number of days. In order to identify hazards and heavy rainfall, the frequency of one day to seven days and more, to 3 parts of short term precipitation include 1 day precipitation, 2 days and 3 days, medium term (4 days and 5 days precipitation) and long-term (6 days and more) was divided. Then, in order to determine the changes in the daily rainfall of each area, first, the average daily rainfall of the short, medium and long run rainfall was calculated and the coefficient of variation of rainfall day and average daily precipitation for each of the areas was obtained. The final map was used in GIS using spatial analysis for zoning. In order to provide the time and spatial distribution pattern of precipitation in each area and to identify the severity of daily precipitation, the ratio of maximum daily rainfall to annual precipitation was calculated and analyzed. In order to compare rainfall variations in the first 15 years of the first 15 years, the coefficient of increasing or decreasing rainfall changes was calculated in two periods. 3. Discussion In area 1 (south and south east of the country), the number of rainy days, the average rainfall of short-term days (precipitation of one to three days), and the medium-term (precipitation of four and five days) decreased. The average daily rainfall in this area was 17 days a year. In area two, the number of rainy days and the average amount of short-term and medium-term rainfall have been decreasing. The number of rainy days was 27 days a year with a mean precipitation of 3.1mm. In the third zone (Caspian coastlines), it was shown that the short-term rainy days are increasing, and the long-term and long-term periods of decline are decreasing. The number of overnight days in this area has been the highest (113 days) per year. In area 4, short and medium rainfall is increasing in terms of the number of days of precipitation. However, long-term precipitation (precipitation with 6 and 7 days and more) has been decreasing. The number of days in this area is 74 days (with an average rainfall of 4mm) per year. In zone 5, both short-term and medium-term rainfall showed a decrease in both trends, while the shortened rainfall is also higher in this area. The total number of days in the study period showed a decreasing trend. The annual rainfall in this area is 39 days (with an average rainfall of 2.3mm) per year. In area 6, the number of rainy days and the average daily rainfall (1-3 days) is increasing. Finally, in area 7, the number of overnight days (with a coefficient of 101) and the short run average had an increase. The medium-term and long-term rainfall have declined. The annual rainfall in this area was about 5mm in 66 days with an average rainfall. 4. Conclusions 1. Dry and semi-arid regions of Iran include areas 1, 2 and 5 (Bandar Lengeh, Konarak, Chabahar, Zahedan, Bandar Abbas, Bam, Zabol, Iranshahr, Kish, Abadan, Yazd, Tabas, Fasa, Bushehr, Birjand, Kerman, Kashan, Abadeh, Semnan, Isfahan, Ahvaz, Sabzevar, Qom, Shiraz and Torbat Heydarieh). The number of short-, medium-term precipitation days (precipitation with a 1-day, 2-day and 3-day sequence) and medium-term precipitation (precipitation i) has declined over the course of 30 years. Long-term precipitation (more than 5 days) has not occurred in these areas. The average daily rainfall in arid regions of Iran is 27 days a year. The average daily rainfall of both short and medium term has been decreasing. The average daily rainfall was 2.3mm per day. 2. The northern coast of Iran was designated as area 3. The frequency of short-term barge days and the average rainfall are both incremental. An increasing trend indicated that rainfall has been severe. 9% has been added to the amount of daily precipitation. The daily rainfall in the region is 113 days per year and the average daily precipitation is 22.9mm. 3. Mountainous area includes areas 4, area 6 and 7 (Ardebil, Gorgan, Parsabad, Khoy, Bojnourd, Tabriz, Quchan, Shahroud, Dashan Tepeh, Maraghea, Karaj, Qazvin, Shahrekord, Mashhad, Orumieh, Zanjan, Hamedan, Sanandaj, Yasouj, Ilam, Khorram Abad, Arak, Hamedan Nogheh, Kermanshah and Saqqez). In the statistical period of 30 years in the mountainous areas, the number of days and average rainfall has decreased for the medium and long term, and has been increased by the number of short-term overnight days and short-term average rainfall. The number of rainy days in mountainous areas is 68 days per year and the average daily rainfall is 3.74mm. 4. The ratio of maximum daily rainfall to annual rainfall in all areas is increasing. This indicates heavy rainfall and that rainfall in the region of Iran is rising. Most rainstorms occur within just a few days. Such anomalies in the regime of rainfall, long dryness, destruction of vegetation, followed by flood descendants and the destruction of water and soil resources and human facilities.}, keywords = {Rainfall hazards,Rainfall variations,Daily Precipitation,Precipitation sequence,Showers}, title_fa = {مخاطرات ناشی از تمرکزگرایی بارش در ایران}, abstract_fa = {پایین بودن میزان ریزش‌های جوی، تغییرپذیری بالا، نوسان بارش، از ویژگی بارز آب‌وهوای ایران به شمار می‌رود. هدف این پژوهش مطالعه و بررسی تغییرات تعداد روزهای بارشی، مقدار بارش و تغییرات شدت بارش در بلند مدت در نواحی مختلف ایران است. داده‌های بارش روزانه در طی دوره آماری 30 سال از سازمان هواشناسی کشور برای 53 ایستگاه همدید در نقاط مختلف ایران گرد آوری شد. جهت طبقه‌بندی از نظر دوره تداوم بارش، روزهای بارشی در 7 طبقه، بارش 1 روزه، بارش با توالی دو روز، بارش با توالی سه روز الی بارش با توالی 7 روز بررسی و استخراج گردید. برای تحقق اهداف از روش تحلیل خوشه‌ای (فاصله اقلیدسی و روش ادغام وارد) برای ناحیه‌بندی اقلیمی استفاده شد و درنهایت ایران به هفت ناحیه از نظر متغیرهای تعداد روز بارشی تقسیم گردید. سپس دوره مطالعاتی به دو دوره 15 ساله جهت مقایسه تقسیم شد. برای شناسایی شدت بارش روزانه از نسبت بارش حداکثر روزانه به سالانه استفاده شد. نتایج نشان داد که در اغلب نواحی ایران فراوانی روزهای بارشی کوتاه‌مدت در 15 سال دوم مطالعاتی (2013-1999) نسبت به 15 سال اول (1984-1998) روند افزایشی دارد. این امر نشان می‌دهد که بارندگی‌های شدید و رگباری در گستره ایران در حال افزایش است که می‌تواند ناشی از کاهش تعداد روزهای بارشی به‌ویژه بارش‌های میان‌مدت و بلند مدت (4-5 و بیشتر از شش روز) باشد و بیشینۀ بارش در کوتاه‌مدت (بارش 1- 3 روز) اتفاق می‌افتد.}, keywords_fa = {مخاطرات بارش,تغییرات بارش,بارش روزانه,توالی بارش,رگبار}, url = {https://geoeh.um.ac.ir/article_31596.html}, eprint = {https://geoeh.um.ac.ir/article_31596_da27c6e70c6b8fad259b8ca06cdcd358.pdf} } @article { author = {Siabi, Negar and Sanaeinejad, Seyed Hossein and Ghahraman, Bijan}, title = {Evaluation of Rainfall Data Derived from TRMM Satellite, MM5 Model and Ground Observation using Sapatio-Temporal Analysis in Arid and Semi-Arid Mountainous Area}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {163-179}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.61868}, abstract = {1. Introduction Precise estimates of rainfall in areas with complex geographical features in the field of climatology, agricultural meteorology and hydrology is very important. TRMM satellite is the first international effort to measure rainfall from space reliably (Smith, 2007). Another set of data that has become available in recent years is the output of numerical prediction models. Akter and Islam (2007) used MM5 model for weather prediction especially for rainfall in Bangladesh. They compared MM5 outputs with 3B42RT production of TRMM, rain gage and radar data and concluded that MM5 is reliable for rainfall prediction. Ochoa et al. (2014) compared 3B42 product of TRMM with simulated rainfall data by WRF model. Their results showed that TRMM data is more applicable for presenting spatial distribution of annual rainfall. In addition to the methods of statistical comparison, the similarity algorithm (Herzfeld & Merriam, 1990) was also used in this study. This algorithm compares a large number of data simultaneously, which can be in the form of maps or models output. In Iran, very few studies have compared the output of numerical prediction models with TRMM products of rainfall. The aim of this study was to evaluate and compare the rainfall data using similarity algorithm for different locations and time periods in order to fill a gap in the space-time data. 2. Material and Methods The study area consisted of North Khorasan, Khorasan Razavi and South Khorasan provinces in North East of Iran, which is geographically located between the longitudes of 55 to 61 degrees and latitudes of 30 to 38 degrees. The climate of the area is arid and semi arid. Total area is approximately 313000 square kilometers. In this study, three types of data were used. Ground-based observations used from synoptic and rain-gauge stations of Meteorology Organization. The seventh series products of TRMM 3B42 sensor containing three hours TRMM rainfall data with a spatial resolution of 0.25 degree were downloaded for free from the site of NASA. MM5 model outputs which were in the form of images with a spatial resolution of 0.5× 0.5 degrees for the period of 2000-2010 were also obtained from NASA and NOAA .In this study, KED as a geostatistical method was used to interpolate rainfall. For running geostatistics algorithms, GS + and ArcGIS software were used. Similarity algorithm was executed for each grid point map and the similarity values were derived. After standardization by calculating the similarity value for the entire study area, F network model for similar map was created. In similarity algorithm, closest values to zero indicate a good similarity between the input maps in a specific location and higher values indicate weaker similarity. Standardization algorithms, similarity and analytical software programming in MATLAB were performed for each grid point of the map. 3. Results and Discussion RMSE values for MM5 model were higher in the warm months. The highest RMSE values were obtained in late spring and early summer. This result proved that in the summer, rainfall was predicted less accurately than in the cold months in winter. RMSE values for TRMM showed a reverse pattern with MM5 model output. Maximum amount of RMSE for TRMM was obtained in January with 14 mm per month. The reason for this may be because microwave energy scattering from frozen ice on the ground. The scattering from rain or frozen rain in the atmosphere is similar. Similarity values in the area were scattered with uniform distribution that represents the least significant inter-annual variation is cold seasons. For the warm seasons, in the south and north of the area, similarity values vary from 1 to 2. Results showed that inter-annual variations of rainfall in warm seasons and in central areas is high. One of the reasons for these results can be errors in the observed data. By examining the time series of TRMM images using similarity algorithm, we found that in the cold season, the south zone of the study area had similarity values 0.05 to 0.1 with a uniform distribution of values. However, higher similarity values were obtained for the northern and central areas where the distribution of similarity values was not uniform. Due to these facts, it can be concluded that rainfall production of TRMM data was relatively good in the cold season in south and relatively week in north and central parts of the region. In the warm season the least amount of similarity could be seen in the northeast part of the study area. But generally, TRMM estimated rainfall fairly in the warm season. 4. Conclusion The validation results of MM5 model rainfall and TRMM monthly rainfall images showed that the model predicted rainfall amounts in the cold months better than in the warm months. However unlike the MM5 model, remote sensing images had the highest error in cold months. The reason was the presence of snow and ice on the ground in the cold months of winter. Considering inter-annual and seasonal changes, it became clear that there is much difference between inter-annual remote sensing image changes and the actual amounts of rainfall (KED). Nevertheless the model inter-annual changes were consistent with real data. Inter-annual changes of the model and the station data (KED) were higher in cold season. KED methods also retained spatial variability of rainfall as well as remote sensing data and model output. The estimates, especially above 1500 meters in the central regions, had low precision in the products. The results showed that in the absence of adequate rain gages in the region, MM5 output model and TRMM data could be used to fill the gaps.}, keywords = {MM5,Precipitation,Similarity algorithm,TRMM}, title_fa = {ارزیابی داده‌های بارندگی حاصل از ماهواره TRMM، مدل MM5 و مشاهدات زمینی به صورت مکانی-زمانی در مناطق خشک و نیمه‌خشک کوهستانی}, abstract_fa = {در مواجه با خطر سیل و یا خسارات ناشی از خشکسالی، برآورد میزان بارش و الگوی تغییرات مکانی آن در یک منطقه گسترده، یکی از چالش‌های مهم در علوم هواشناسی، کشاورزی و هیدرولوژی است. اندازه‌گیری محلی بارندگی در مناطق دور افتاده به دلیل هزینه زیاد و محدودیت‌های عملیاتی دشوار است. بدین علت در تحقیق حاضر به‌منظور تعیین الگوی مکانی-زمانی بارش و امکان تلفیق داده‌ها، سه نوع مختلف از تولیدات بارندگی شامل داده‌های ماهواره‌ای (TRMM3B42)، داده‌های حاصل از مدل پیش‌بینی عددی جوّی (MM5) و اندازه‌گیری‌های زمینی (نقشه‌های حاصل از روش زمین‌آمار (KED))، مورد مطالعه قرار گرفتند. این مطالعه در بازه زمانی سال‌های 2000 تا 2010 میلادی و برای منطقه شمال شرق ایران به صورت ماهانه، فصلی و سالانه انجام شد. داده‌ها با استفاده از شاخص اعتبارسنجی RMSE و الگوریتم تشابه با یکدیگر مقایسه شدند. نتایج نشان دادند که یکی از ضعف‌های روش زمین‌آمار نبودن اطلاعات کافی در ارتفاعات بالای (1500) متر منطقه است. همچنین دقت تصاویر ماهواره‌ای در فصل‌های گرم بیشتر بود؛ بطوریکه در ماه آگوست مقدار 7/1 RMSE = به دست آمد. در فصل زمستان (ماه ژانویه) بیشترین مقدار 02/14 RMSE = حاصل شد که این امر عملکرد ضعیف تولیدات ماهواره‌ای TRMM در مناطق پوشیده از یخ را نشان می‌دهد. در اعتبارسنجی مدل MM5 بیشترین و کمترین مقدار RMSE به ترتیب 64/6 و 05/1 به دست آمد. علاوه بر این مدل MM5 تا حدود زیادی در شبیه‌سازی مقادیر بارندگی سالانه بیش‌برآورد داشت. نتایج تحلیل‌های مکانی- زمانی الگوریتم تشابه نیز نشان دادند که عملکرد مدل MM5 در مقیاس ماهانه و فصلی و تعیین مناطق بارندگی بهتر از تصاویر ماهواره‌ای TRMM بود. همچنین هر سه محصول الگوی مکانی بارندگی در مقیاس فصلی و سالانه را به‌خوبی نشان دادند.}, keywords_fa = {الگوریتم تشابه,بارندگی,TRMM}, url = {https://geoeh.um.ac.ir/article_31616.html}, eprint = {https://geoeh.um.ac.ir/article_31616_f62903da399576b1486b3e138ad95f80.pdf} } @article { author = {Kashki, Abdolreza}, title = {Analysis of the Polar Vortex Trend in the Northern Hemisphere under Climate Change Conditions}, journal = {Journal of Geography and Environmental Hazards}, volume = {6}, number = {3}, pages = {181-197}, year = {2017}, publisher = {Ferdowsi University of Mashhad}, issn = {2322-1682}, eissn = {2383-3076}, doi = {10.22067/geo.v6i3.62149}, abstract = {1. Introduction Today, climate change problem is considered as one of the most common scientific subject, even as social and political issues, in fact it is not novelty issue. Principally, because the change and movement are one of the component in macro scale climatic systems, discovering the legitimacy of these systems, which mainly is cyclic, it is can be consider as a tool which can help to predict future behavior of the system. The polar vortex (PV) is defined as a large-scale upper-level cyclonic circulation in the middle and upper troposphere which is centered on the polar region. Measurement undertaken, observational investigation and modeling indicate the oscillation cycles of polar vortex. There are two effective mechanisms for oscillation cycles of polar vortex that could be divided into two categories: internal and external. The internal mechanism is included investigation of oscillation cycles of polar vortex by applying thermal and wavy forcing, which is independent of time and leads to identify the effect of the stratosphere on the troposphere. External mechanism is included investigation of oscillation cycles of polar vortex by applying thermal and wavy forcing, which is depends on time and leads to identify the effect of the troposphere on the stratosphere. Trend changes on the macro scale climatic system, such as polar vortex has a significant role on climate change of the surface. Variability in the atmospheric circulation at the hemispheric-scale can have a direct impact on variations in the surface environmental parameters, such as temperature, precipitation, and pollutant transport. One indicator of the behavior of the hemispheric-scale circulation is the polar vortex. The polar vortex can be used for study the holistic hemispheric-scale sub-tropical circulation because it represents the characteristics of long-wave, upper-level ridge-trough configuration around the entire (northern or southern) hemisphere at a given point in time. The PV is defined as the large-scale upper-level cyclonic circulation in the middle and upper troposphere centered on the polar region. The most fundamental question addressed in this research is whether the northern hemisphere polar vortex (NHPV) exhibits long-term trends in area over the 1948-2007 periods. Therefore, the first part of this study answers the question: How can we characterize the long-term trend of the area of the NHPV? It is hypothesized that the global warming signal would be associated with a reduction in area in the NHPV over time as the cold pool of air over the poles shrinks. 2. Material and Methods In this research, daily mean data of 500 hPa geopotential height were used from the National Center for Environmental Prediction & National Center of Atmospheric Research (NCEP/NCAR) during the period of 1948 to 2007. Their spatial resolution is 2/5 * 2/5 degree with 36 * 144 pixels. The 500 hPa geopotential height (i.e., constant pressure surface) was selected for analysis for several reasons. First, since the 500 hPa level is in the middle of the atmosphere, it represents characteristics of both the lower and upper atmosphere. Also, most steering of mid-latitude systems occurs at the 500 hPa level and geostrophic flow occurs at this level as well. A specific isohypse(contour) is selected to represent the NHPV for each month in 500 hpa level (table 1). Table (1): specific isohypse of polar vortex for each month in 500 hpa level Month Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec Specific isohypse(gpm) 5460 5460 5520 5580 5640 5700 5700 5760 5640 5580 5520 5460 Choi & et al. (2009) Monthly polar vortex area is calculated with Grads software. This research utilizes a statistical approach to determine the trend in the northern hemisphere (NH) polar vortex. For comparison of area means, used from Paired-Samples T Test and for the detection of polar vortex area trend used from Kendall's tau trend test in SPSS software. Paired-Samples T Test is one of the statistical parametric tests to compare the mean and variance of the two dependent groups in a region. 3. Results and Discussion By doing the Kendall tau test in SPSS, it was determined a reduction in the polar vortex area in all months. Polar vortex area has a decreasing trend during May, June, July, August, September and March which is significant at 0.01 level. The biggest reduction trend is related to August and lowest to December. The results show that the polar vortex during the whole period is declining, but this decline was higher during summer months. The most of decline in the polar vortex area is observed in August that the rate of about 93,000 square kilometers per year. The decline rate has accelerated in the second half of period. Generally, the decline of polar vortex area caused by macro-scale climate change and planetary scale, That certainly global warming and consequently advancement of subtropical high pressure will be one of the components. The results of Paired-Samples Test showed that the mean difference of polar vortex area is negative for all months and this amount represents a reduction in polar vortex area during thirty years of second period compared to the first period. 4. Conclusion The change in configuration of polar vortex (trough and ridge) and transformation from zonal to meridional as a result of reducing of meridional pressure gradient caused regional climatic anomalies such as the change in the type and amount of precipitation and temperature. Generally, the decline of polar vortex area caused by macro-scale climate change and planetary Scale, that certainly global warming and consequently advancement of subtropical high pressure will be one of the effective components.}, keywords = {Polar Vortex,Trend analysis,Climate change,Northern Hemisphere}, title_fa = {واکاوی روند تاوۀ قطبی در نیمکرۀ شمالی تحت شرایط تغییر اقلیم}, abstract_fa = {تغییر روند سامانه‌های کلان مقیاس اقلیمی همچون تاوه قطبی، نقش بسزایی در تغییر اقلیم سطح زمین دارد. در این پژوهش برای نیل به این هدف، از داده‌های دوباره واکاوی شده ارتفاع ‌ژئوپتانسیل تراز میانی جو از مرکز ملی جو و اقیانوس‌شناسی ایالات‌متحده آمریکا استفاده شده است. این داده‌ها دارای تفکیک مکانی 5/2×5/2 درجه قوسی و به صورت میانگین روزانه برداشت گردیده است. دوره آماری این پژوهش از سال 1948 تا 2007 میلادی برای نیمکره شمالی بوده و شامل 144×36 یاخته است. برای مقایسه میانگین‌ها، از آزمون تی- تست برای دو گروه وابسته و جهت بررسی روند تاوه قطبی از آزمون روند کندال تاو استفاده گردید. نتایج پژوهش نشان داد که تاوه قطبی در ماه‌های اردیبهشت، خرداد، تیر، مرداد، شهریور و اسفندماه، دارای روند کاهشی (منفی) در سطح معنی‌داری 01/0 است. البته علل کاهش سطح تاوه قطبی در نیمه سرد سال و به‌ویژه در بهمن‌ماه و اسفندماه نیز قابل تأمل است. همچنین در تمام ماه‌های مورد بررسی، سطح تاوه قطبی کاهش یافته و سیر نزولی داشته که عموماً این سیر کاهشی، در نیمۀ گرم سال بیشتر از نیمه‌سرد سال است. این تغییرات باعث ناهنجاری در الگوهای آب‌وهوایی مناطق می‌گردد.}, keywords_fa = {قطبی,تحلیل روند,تغییر اقلیم,نیمکره شمالی}, url = {https://geoeh.um.ac.ir/article_31643.html}, eprint = {https://geoeh.um.ac.ir/article_31643_ab6fe355642f869dc0d5e640a0c70120.pdf} }