@article { author = {ali Jahan, mehdi and Salahi, Broumand and Ghavidel Rahimi, Yusof and Farajzadeh Asl, Manuchehr}, title = {A new approach in the identification and analysis of cold waves, Case Study: North East Iran}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {1-14}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = {One of the most important issues that human societies are currently facing is the phenomenon of climate change that attracted the attention of many researchers around the world. One of the effects of climate change is the increase in the frequency and severity of occurrence of extreme weather events, such as frost temperatures and extreme rainfall. The effects of climate change on changes in cold-wave temperatures in recent years, as well as the effects of cold waves on various aspects of human societies, have always been the concern of various scholars in most parts of the world, including cold weather, and atmospheric hazards. Several definitions of cold waves are presented. In general, scientists used cold weather or cold weather for at least 2 days or more at temperatures below zero degrees Celsius. In general, the characteristics of the cold wave can be summarized in three characteristics: 1. the intensity and velocity of the temperature drop 2. the numerical value of the drop or deviation in the daily temperature value 3. the duration of the continuity (time continuity) of the cold wave. Materials and methods For the purpose of this research, data from the upper levels of the atmosphere were used to analyze the data of the 20th century. The data listed on the website was https://www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2.html and was used. NASA's Twentieth Century Data has a good place in comparison with the normal data from time separation, and has a better and more accurate accuracy than it is. The data used are 142 years old from 1871 to 2012. The data are 6 hours and 4 daily observations (0, 6, 12 and 18 Zulu) with spatial resolution of 2 degrees longitude at 2 degrees latitude and 24 pressure levels from 1000 to 10 hPa. For the purpose of this study, at first, the cold waves with a minimum temperature of -15 ° C and continuity of time for at least 2 days in 142 years of statistical period were extracted from a minimum of two-meter surface temperature data. Then the relevant data was categorized in terms of frequency, severity, duration and spatial extent. In order to validate the extracted data, they were controlled to the point where they met the ground stations and ensured the accuracy of the data. For synoptic analysis, the coldest waves occurred in each of the months. For this purpose, combinational maps of ground pressure, geopotential heights and wind current of 500 hPa, bar thickness map, temperature map, and a minimum temperature of two meters of ground level were used. Results and discussion The results of the synoptic analysis of the selected days indicate the dominance of the high-pressure system on the surface of the earth and the collapse of the block, followed by the cavern and stack at the upper levels of the atmosphere. In most of the study days, the high pressure (Siberian high-pressure migratory force) system in the Earth has been flowing on the Earth's surface, which has intensified its intensity. The meridian flow formed by the flood-blocking blocks has led to a very cold, northwest northern part of Iran's cold air and, on the other hand, has increased the duration of the deployment of these cold waves. Conclusion According to the results, 44 cold currents at -15 ° C and colder in the north east of the country were identified during the studied time period. The waves are mostly due to January, February and December. Which is very good for the influence of Siberian cold pressures, shows such waves. A noticeable decrease has occurred in these waves from 1907 onwards. The frequency of these waves has decreased over the years, but has been added to the severity and duration of its deployment. According to the results of the studies, it can be said that changes in the process of cold weather are not related to global warming and climate change. This cold wave is formed in most cases when the Siberian high-pressure earth is merged with the Western Immigrant High.On the other hand, in the upper levels of the atmosphere, due to the high surface pressure of the western winds, they collide with blocking barriers and convert the orbital flow of the western wind to a meridian stream. The process mentioned above leads to the formation of a heap over Eastern Europe to the middle of the Red Sea and the formation of a ravine over the Mediterranean and Turkey. As explained above, it leads to the very cold weather flowing north to the northern part of Iran. Also, the thinness of barley thickness over the atmosphere of northeastern Iran formed as a result of a very cold, semi-arctic flow; the very cold weather has dominated the northern latitudes for several days. The study of temperature patterns indicates the domination of the northern and northwest winds, and also indicates an increase in the cold intensity of the waves occurring with the increase of the latitude of the source. Very cool temperatures occur when the source of cold air is from latitudes above 60 degrees.}, keywords = {Cold waves,NASA 20th Century data,-15C temperature,North West of Iran}, title_fa = {رویکردی نوین در شناسایی و تحلیل امواج سرمایی مطالعه موردی: شمال شرق ایران}, abstract_fa = {پدیده تغییر اقلیم یکی از مهم‌ترین مسائلی است که جوامع بشری با آن روبرو هستند. افزایش فراوانی و شدت رخداد رویدادهای فرین اقلیمی هم­چون دماهای فرین و بارش­­های شدی از جمله اثرات تغییرات اقلیمی به شمار میروند. تحقیق پیش­رو با رویکردی نوین به شناسایی، بررسی و تحلیل سینوپتیک امواج سرمایی با دمای 15- درجه سانتی­گراد و سردتر در شمال شرق ایران می­پردازد. این پژوهش با استفاده از داده­های قرن بیستم سازمان ناسا، در بازه زمانی 142 ساله (2012 – 1871 میلادی) به انجام رسیده است. ابتدا امواج رخ­داده در طول بازه زمانی مورد مطالعه شناسایی، بررسی و نهایتاً سردترین روز موجِ شناسایی شده از ماه­های رخ­داده انتخاب و مورد تحلیل سینوپتیک قرار گرفت. نتایج حاصل شده از تحلیل­های سینوپتیک روزهای انتخابی حاکی از تسلط سیستم پرفشار در سطح زمین و رخداد بلوکینگ و به دنبال آن ناوه و پشته در سطوح فوقانی جو دارد. در اکثر روزهای مورد مطالعه، سیستم پرفشار ادغامی (پرفشار سیبری – پرفشار مهاجر غربی) در سطح زمین جریان داشته که بر شدت سرمای سطح زمین به شدت افزوده است. جریان نصف­النهاری شکل گرفته توسط بلوکینگ­های رخ­داده منجر به وزش هوای بسیار سرد عرض­های شمالی به شمال شرق ایران شده و از طرفی دیگر بر مدت زمان استقرار این امواج سرد افزوده است}, keywords_fa = {امواج سرمایی,داده‌های قرن بیستم ناسا,دمای 15- درجه سانتی‌گراد,شمال شرق ایران}, url = {https://clima.irimo.ir/article_77175.html}, eprint = {https://clima.irimo.ir/article_77175_c2765a9ee265542bf6d26da3ea8f2d4b.pdf} } @article { author = {Javanmard, sohaila and Tajbakhsh, sahar and bodagh jamali, javad}, title = {Climatology of low level clouds occurrence over Iran (1981-2010)}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {15-32}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = {This paper is aimed at climatological study of low level clouds in four seasons and accordance to the long-term pattern for operational cloud seeding over Iran. Clouds are observed in different shapes and heights in the atmosphere. Regarding the classification of clouds there are various ideas. Based on the Howard classification 10 types of clouds are classified in 4 groups based on   the height of  cloud base from surface includes low with height of less than 6500 ft, middle with height of 6500-16000 ft, high with 16000-18000 ft, and vertical development.  Cloud climatology is main part of weather modification program for cloud seeding site selection. In this study, frequency of occurrences of low level cloud including Stratocumulus (Sc.), Stratus (St), Cumulus (Cu) occurrence have been collected from 44 synoptic stations of Iranian Meteorological Organization (IRIMO) for 30 years (1981-2010)   for day time including 06, 09, 12, and 15 UTC and CFSR[1] data with 0.5 degree resolution have been used for deriving of long term seasonal pattern. Seasonal mean of geopotential height, temperature, horizontal wind, vertical wind at 500 hPa, surface pressure and precipitable water (PW) in (500-1000) hPa layer have been derived.  Investigations have been carried out based on location of province and watershed basins. The most important investigating results show that low level clouds occurrence with less than %30, have not been observed in selected stations in cold season including autumn and winter . The Northwest, North, and Northeast provinces and basins have high (>%70) low level clouds occurrence in all months which have suitable condition for operational cloud seeding with respect to this index. Low clouds occurrences in warm season including spring and summer show that southern part of Iran have low  (<%30) to medium (%30-%70) but were high (>%70) for other stations which detail information of Southern provinces are as following; provinces including Hormozgan , Bushehr, Sistan-Baluchestan and Khuzestan,  Kerman, Fars , and South Khorasan are between %30 -%70. Maximum of low cloud occurrence belongs to spring, autumn, winter, and summer respectively. Maximum of cloudiness belongs to March and April in spring. The percent of low level cloud occurrence in southern basins in most months were low (<%30) which achieved very low score for operational cloud seeding with respect to this index. Long term atmospheric pattern shows suitable condition for amplification of cloudiness in clod seasons which accompanied with falling of cold weather Siberian high pressure and amplification of the warm Southern flow provide suitable condition for enhancement of humidity specially for west part of country. Formation of thermal low pressure in summer season, coverage of level cloud and precipitable water reduces over region. In cold seasons (roughly autumn and winter) maximum of low cloud occurs at Bandar- Anzali station in Gilan Province with max of 93.03% and Ramsar station in Mazandaran province with max of 94.34% which both occur in October. In the warm season (roughly spring and summer) is related to Ramsar station with Max of 99.10% and Noshahr station with 98.72 % which both occur in September. The minimum of low cloud occurrence is related to Zabol station in Sistan- Baluchestan province with 32.88% and Iranshahr station in Sistan- Baluchestan province with 37.93% in clod season which both occur in October. In warm season Bushehr station in Bushehr province and Abadan station in Khuzestan province have 15.79% and 16.34% respectively which both occur in September. Due to location of Caspian Sea in North of Iran and Alborz Mountain in southern part of it, therefore the most low level clouds occur in moist and rainy climate.  Long term surface pressure pattern show formation of suitable condition for amplification of cloudiness amount  in cold season which with falling of cold weather in North and Northwest associated with Siberian high pressure and amplification of warm and humid weather provide suitable condition for increasing of humidity specially in Midwest of country. Formation of thermal low pressure at the surface causes decreasing of coverage of low cloud and precipitable water over the region in summer. Although application of satellite data for investigating of clouds is prevalent due to their expand coverage, but the accuracy and importance of surface observation is not deniable. However, in order to achieve more accurate mapping of low level cloud over Iran, due to the shortage of number of synoptic stations with long term observation using satellite data is necessary.   Key words: Low Cloud, Cloud Seeding, Watershed Basin, Long Term Climate Pattern, and Cloudiness }, keywords = {Low Cloud,Cloud Seeding,Watershed Basin,Long Term Climate Pattern,and Cloudiness}, title_fa = {اقلیم شناسی رخداد پوشش ابرهای پائین در ایران (2010-1981)}, abstract_fa = {    هدف از انجام این مطالعه، اقلیم شناسی ابرهای پائین در فصول مختلف سال و تطبیق آنها با الگوهای بلند مدت جوی به منظور کاربری در عملیات بارورسازی ابرها در ایران می باشد. داده های فراوانی رخداد ابرهای پائین شامل پوشن کومه‌ای (استراتوکومولوس)، پوشنی (استراتوس)، و کومه ای (کومولوس) از 44 ایستگاه همدیدی سازمان هواشناسی کشور در بازه زمانی 30 ساله در طول روز  شامل ساعات 06، 09، 12، و 15UTCگرد آوری شده اند و برای رسم الگوهای بلند مدت فصلی پارامترهای جوی از داده های[1]CFSR استفاده شده است. بررسی ها هم به صورت استانی و هم بر اساس موقعیت حوضه های آبریز صورت پذیرفته است. مهمترین نتایج این بررسی نشان می دهد که ابرهای پائین با رخداد بیشتر از 30% در ایستگاه های منتخب در فصول سرد سال شامل زمستان و پاییز مشاهده گردید. حوضه­ها و استانهای شمال­غرب، شمال و شمال­شرق کشور در تمامی ماه­ها از درصد رخداد ابر بالایی ( بیشتر از 70%) برخوردارند که از نظر این ویژگی این مناطق شرایط مناسبی برای انجام عملیات بارورسازی ابرها دارند. در حوضه های واقع در جنوب شرق کشور در بیشتر ماه­ها درصد رخداد ابر پایین کمتر از %30 بوده بنابراین شانس کمتری برای عملیات باروری دارند.الگوهای بلند مدت جوی شکل گیری شرایط مساعدی را برای تقویت میزان ابرناکی در فصول سرد سال نشان می دهند که با ریزش هوای سرد در نواحی شمالی و شمال غربی همراه با پرفشار سیبری و تقویت هوای گرم و مرطوب جنوبی شرایط مساعدی برای افزایش رطوبت به ویژه در نیمه غربی کشور فراهم می کند. با شکل گیری کم فشار گرمایی در سطح زمین در فصل تابستان، پوشش ابرهای پایین و آب قابل بارش در کل منطقه کاهش می یابد.}, keywords_fa = {ابر پائین,بارورسازی ابرها,حوضه آبریز,الگوی میانگین بلند مدت جوی,و ابرناکی}, url = {https://clima.irimo.ir/article_77179.html}, eprint = {https://clima.irimo.ir/article_77179_977fc5a6b1537bfe2070333033392a7b.pdf} } @article { author = {Rahimzadegan, Majid and Hasanloo, Hamed and Mobasheri, MohammadReza}, title = {Digital mapping of soil featured using remote sensing data}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {33-42}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = {Abstract Introduction: Digital soil mapping is achieved using different data and methods in integrated methods. These methods determine the spatial and temporal distribution of soil features. Digital soil mapping can fill the gaps in the knowledge and data of soil in recent years. In early 2000, some effective factors have led to the more successes of the digital soil mapping including: 1) increasing the access to the spatial data such as satellite images, Digital elevation models (DEM), and increasing the number of available maps, 2) increasing the computational abilities in data processing, and 3) development of the data mining tools and Geographic Information Systems (GIS). Moreover, increasing the global demand to reduce uncertainties in the spatial data, repairing existing maps, and the help of global organizations in development of methods are among the other effective factors. Materials and methods: Theoretical framework of digital soil mapping was introduced in a large number of researches. In this research, some aspects of digital soil mapping were represented including the structure, history, and explanation of some of its parts. In this regard, two main categories exist including sensing the soil properties close to the soil and soil remote sensing. In the latter one, the most important method is soil spectroscopy. However, soil spectroscopy encountered some problems such as complexity of the spectrum of soil components and overlapping the spectrum of those components. Results and discussion: The results showed that the digital soil mapping requires three fundamental parts including: 1) the costs in the form of field campaigns and laboratory observation methods, 2) the process of utilizing spatial and non-spatial inference systems of the soil, and 3) output parts in the form of soil geospatial information systems which include outputs in the form of forecasting rasters along with their uncertainties.  Conclusion: The results indicate the success of the proposed methods. Moreover, the developments of digital soil mapping is composed of the access to digital spatial data, abilities in bulk data processing, prevalence of data mining tools, improving the GIS systems, and utilizing geostatistic methods. Furthermore, extracted data from remote sensing data such Landsat, Spot, MODIS, NOAA AVHRR, and IKONOS images can be helpful. However, calibrating satellite data require laboratory measurement such as soil spectrometry.}, keywords = {Soil,Map,Digitizing,Remote Sensing}, title_fa = {نقشه‌سازی رقومی ویژگی‌های خاک با استفاده از داده‌ی سنجش از دوری}, abstract_fa = {     نقشه­سازی رقومی خاک با پیشرفت­هایی که در دهه­های گذشته داشته است، توانسته است شکاف­هایی که در دانش و داده خاک وجود داشته است را پر کند.  در اوایل سال 2000 میلادی با پیوند چند عامل، شامل افزایش دسترسی به داده مکانی (مدل ارتفاعی رقومی (DEM)، تصاویر ماهواره ای)، دسترسی به توان بالای محاسباتی برای پردازش داده­ها، پیشرفت ابزارهای داده­کاوی و GIS،  کاربردهای فراوان زمین آمار باعث موفقیت بیش از پیش نقشه­سازی رقومی خاک شد. علاوه براین، افزایش تقاضای جهانی برای کاهش عدم قطعیت­های داده مکانی و بازسازی بسیاری از نقشه­برداری های انجام شده و کمک سازمان­های جهانی که در گسترش روش­ها و دانش نقشه­سازی رقومی نقش بسزایی داشتند، از دیگر موارد موفقیت در این زمینه بود. قالب نظری نقشه­سازی رقومی خاک تاکنون در تعداد زیادی از مقاله­ها بیان شده است. در این پژوهش،  به ساختار نقشه­سازی رقومی خاک، تاریخ،  توضیح برخی قسمت­های آن پرداخته شده­است. نقشه­سازی رقومی خاک نیازمند سه بخش اساسی است: بخش هزینه در قالب عملیات زمینی و روش­های مشاهداتی آزمایشگاهی، فرآیند بکارگیری سیستم­های استنتاج مکانی و غیرمکانی خاک،  بخش خروجی در قالب سیستم های اطلاعات مکانی خاک، که شامل خروجی­هایی در قالب رسترهای پیش بینی با عدم­قطعیت آن است که در این نوشتار به آن پرداخته شده و راه­کارهای رفع مشکلات ارائه شده­است. خروجی کار از موفقیت این دستاورد حکایت می­کند.}, keywords_fa = {خاک,نقشه,رقومی سازی,سنجش از دور}, url = {https://clima.irimo.ir/article_77184.html}, eprint = {https://clima.irimo.ir/article_77184_92eb28e018f34973b81bb6c8501d19f4.pdf} } @article { author = {Chiniforosh, Navid and Latif Shabgahi, Gholamreza}, title = {Wind measuring devices: challenges, methods and technology trend}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {43-62}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = {Introduction Wind is known as an intermittent event because of its rapid change in direction and value. Various effects of storm on civil aviation, besides of its danger to the urban, industrial and agricultural areas, make it very important to forecast wind in appreciate lead time. Direct effect of wind on many industries, specially its role in energy generation and increasing share of wind energy in the market, made it very important. High penetration of wind power in the electricity system provides many challenges to the power system operators, mainly due to the unpredictability and variability of wind power generation. Material and methods Different kind of observation systems including in-situ devices and remote sensing devices are useful to measure wind, and different methods are useful to detect and estimate probability of extreme events as well as forecast the wind speed. Different methods for detection and forecasting of wind have been invented and several works were done for comparing and improving them. In-situ measuring devices include, cup anemometer, ultrasonic anemometer and hotwire anemometer, while remote sensing measuring devices include, SODAR, LiDAR and radar. SODAR, LiDAR and radar operate in a similar manner except that they use different kind of pulses for transition. Generally, both the intensity and the Doppler frequency shift of the return signal are analyzed to determine wind speed, wind direction and turbulence. In spite of in-situ measuring instruments which measure the wind at a single point, remote sensing devices measure the wind in several points or a limited area. Each measuring device has its advantage and limitations witch has been listed in the paper. Wind farm deployment is moving from flat to complex terrains because of the availability of stronger winds there. The cost of site assessment through local sensing techniques is also growing due to the increasing height of meteorological masts. The maintenance required after installing the setup makes this approach even more expensive. On the other hand, remote sensing technologies are cheaper solutions, but their accuracy in complex terrains is still questionable. Turbulence also needs to be considered when measuring the wind. Turbulence is caused by (i) friction with the earth’s surface, that is flow disturbances caused by the topographical features and (ii) thermal effects that can cause air masses to move vertically as a result of variations in temperature. Turbulent flow is chaotic with a variable pattern over a short time frame but it has a relatively constant average over longer time periods. Wind turbulence is the rapid disturbances or irregularities in the wind speed, direction, and vertical component. The most common indicator of turbulence is the standard deviation (σ) of wind speed. σ normalized with the average wind speed gives the Turbulence Intensity (TI) of a site. Results and discussion Various methods classified according to time-scales or methodology, are available for wind forecasting. According to the time-scales, wind forecasting methods can be divided into 4 categories. (i) ultra-short-term forecasting: from few minutes to 1 hour ahead, (ii) Short-term forecasting: from 1 hour to several hours ahead, (iii) medium-term forecasting: from several hours to 1 week ahead and (iv)long-term forecasting: from 1 week to 1 year or more ahead. Each category has its own application in industry. The rapid increase in numbers of  connectable devices, the expansion of networks, the implementation of new networks, and the requirement for field workers to be completely mobile but always connected (with laptops, smart tablets, smart phones), makes even more imperative the implementation of some form of Unified Communications. Otherwise it takes too long to adapt to changes. Under this paradigm the communications medium from the central server to a remote station, and around the remote station may still be varied (fibre, cable, cellular, satellite, ADSL, Radio, Microwave, WiFi, Ethernet etc.). However the interconnection method between the different medium link modules is all the same - Ethernet, with Power over Ethernet (PoE) where practicable. New frameworks in observation systems like IOT (Internet Of Things), make a revolution in measuring methods along with data transfer. In IOT, all of the data sources (sensors), end user devices (displays, databases), and even a data source and sink (an actuator, smart phone) are connected to the Internet and have two ways communication. Conclusion  This paper review the wind measuring devices along with the new frameworks of measuring methods like IOT and then presents a comparison between different wind forecasting methods. Spatial correlation method has been depicted by use of measured data of two ultrasonic wind sensors of IKIA (Imam Khomeini International Airport) in March 31st 2015. Results show strong dependencies of the observed data of two sites, and wind speed and direction in second site, follow the first site with a delay. Comparison between wind measurement by radiosonde and VVP and CAPPI products of S-band weather radar in Ahwaz shows good consistency at higher at elevation.}, keywords = {wind sensor,RADAR,Turbulence,wind shear,Remote Sensing}, title_fa = {تجهیزات انداز‌ه‌گیری سرعت و جهت باد: روش‌ها، چالش‌ها و روند فنّاوری}, abstract_fa = {    باد پدیده­ای نامنظم است که سبب برخی از پدیده­های جوی می­شود و تغییراتی شدید و ناگهانی دارد. اثرات مختلفی که تندبادها بر پرواز هواپیماها دارند در کنار خطرات ناشی از توفان برای مناطق مسکونی و صنعتی و کشاورزی، همچنین اثر گذاری مستقیم باد بر بسیاری از صنایع از جمله نیروگاه­های بادی، ضرورت بررسی بیشتر عنصر باد را ایجاب می­کند. ابزارهای اندازه­گیری باد از جمله ابزار سنجش در محل، مانند بادسنج­ و سنجش از دور مانند رادار، هر یک با قابلیت­ها و الزامات خاص خود، در سنجش باد بکار گرفته می­شوند. روش­های متنوعی نیز برای کشف پدیده­های مرتبط و پیش­بینی این پدیده­ها در کنار پیش­بینی کمّی سرعت و جهت باد ابداع شده و مورد استفاده قرار گرفته­اند.  این مقاله در کنار گذری بر مفاهیم مرتبط نظیر تلاطم و چینش باد، ابزارهای سنجش در محل و سنجش از دور سرعت و جهت باد را بررسی کرده و چارچوب­های نوین اندازه­گیری سرعت و جهت باد، شامل روش­های هوشمند و مبتنی بر اینترنت اشیا که موجب تحولی در امر داده­برداری و دریافت و نمایش داده­ها شده است را معرفی و مقایسه­ای بین روش­های پیش­بینی باد ارائه می­کند. همچنین در این مقاله مقایسه­ای بین روش سنجش در محل (استفاده از داده­های باد اندازه­گیری شده توسط رادیوسوند) و روش سنجش از راه دور (داده­های VVP و CAPPI تولید شده توسط رادار داپلر باند S  در اهواز) صورت گرفته است که  نتایج نشان می­دهد که در ارتفاعات بالا این دو مقدار به هم نزدیک شده و میزان اختلاف به حداقل می­رسد.}, keywords_fa = {بادسنج,رادار,تلاطم,چینش باد,سنجش از دور}, url = {https://clima.irimo.ir/article_77185.html}, eprint = {https://clima.irimo.ir/article_77185_f6f291e750d365d4005ec5a3010d214c.pdf} } @article { author = {GHolizadeh, MohammadHossein}, title = {Analyzing variance amount and time of occurrence of precipitation at Ilam synoptic station}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {63-76}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = { Introduction Taking into consideration that Iran is the world's desert belt and has a semi-arid and dry climate, the most important climatic issues focus on lack of rainfall, shortage of water resources and atmospheric elements of climatic instability. Because rainfall is the most variable climatic element in Iran and supplies water resources, natural ecosystems and the environment, the change in the characteristics of precipitation due to unstable sources is dependent on it. Since in Ilam province, the economy is based on agriculture, change in the amount and time of rainfall affects the economy and society. For awareness of this important subject some studies cited explore the spatial variations of one-day rainfall in providing rainy days and amount of precipitation in Iran which showed that in a quarter of the whole of Iran had a decreased share in providing rainy days and only 3 percent of Iran increased their share (Nazarpour et al.,2012).The variance in the retention of precipitation in Kurdistan Province indicate that the share of short-term survival of rainy days and providing the amount of precipitation in the eastern half of the province is declining  (Darand, 2014).The results of studies carried out in the context of changes in seasonal and annual rainfall in Iran have indicated rainy season precipitation decrease and increase of seasons with low precipitation (Asakereh and Razmi, 2012, Mofidi,et al., 2012, Negaresh et al., 2012, Mohammadi., 2013, Movahdi et al., 2013, Masoodian and Darand, 2013).The findings of the study of precipitation and drought in southern Italy showed that annual rainfall has decreased and the process of decreasing rainfall in winter is greater than other seasons (Marco and Federico, 2004). Studies examining rainfall trends in the Czech Republic and Slovakia has demonstrated an overall increase in rainfall variability at all scales (Bodri et al., 2005). Evaluation of heavy rains in China has revealed an increase in average annual rainfall in the south west, North West and east of China and a decreasing trend of rainfall in central and north eastern parts (Gong et al., 2004). Evaluation of daily precipitation in the Yangtze River basin illustrated increased summer rainfall, particularly in June and July (Jing Tong et al., 2007). Examination of the two scales of monthly and seasonal rainfall in Turkey showed more stations to record negative winter precipitation trends while higher precipitation rates was observed in other seasons (Kahya and Partal, 2007). Data and Methodology In this study, daily precipitation data of Ilam synoptic station in the period 22/05/1986 to 21/09/2012 was used. Homogeneous and heterogeneous precipitation data was evaluated using two tests: the cumulative deviation test and Worsley's Maximum Test. Significant data trends were calculated using the nonparametric Mann- Kendall test.A slope estimator was used to estimate the slope. Leap year in the time series of monthly precipitation amounts was identified with the help of the homogeneity tests mentioned and significant differences in mean time series before and after leap year was evaluated using the Mann Whitney test.   Resultes and Discusión In this study, variance estimation of the amount and time of precipitation at Ilam synoptic station was performed. The results showed that the amount and time of rainfall during cold and rainy seasons in Ilam station decreased. Thus, precipitation rates of months with higher precipitation also decreased. By comparing the findings of previous research conducted, the results of this study can be confirmed. Exploring the spatial variations of one-day rainfall in providing rainy days and amount of precipitation in Iran showed That in a quarter of the extent of Iran their share in providing rainy days decreased and only 3 percent of Iran on their share has increased(Nazarpour et al.,2012). The variance in the retention of precipitation in Kurdistan province indicate that the share of short-term survival rainy days and providing the amount of precipitation eastern half of the province is declining (Darand., 2014). The results of studies carried out in the context of changes in seasonal and annual rainfall in Iran indicated procedure rainy season precipitation decrease and increased their season with low precipitation(Kaviani and Asakereh, 2005, Mofidi, et al., 2012,Negaresh et al., 2012, Mohammadi., 2013, Movahdi et al., 2013, Masoodian and Darand, 2013). The findings of the study of precipitation and drought in southern Italy using data annually, monthly, daily, showed that annual rainfall has decreased and process of decreasing rainfall in the winter is more than other seasons (Marco and Federico, 2004). Evaluation of daily precipitation in the Yangtze River basin by Mann-Kendall and regression Increased summer rainfall, especially in June and July revealed (Tong Jing et al., 2007). Examination of the two scale monthly and seasonal rainfall in Turkey, more Stations in winter precipitation trends were negative. However, increasing precipitation was obtained in other seasons (Kahya and Partal, 2007). Conclusion The findings of this study showed that the amount of precipitation received during the study period in months of high precipitation at Ilam station has fallen while the amount of precipitation received in months of low rainfall and dry months, showed an increasing trend. The maximum reduced rate of precipitation received was in March. In this month, the average rate of rainfall decreased by 3/61 mm for each year. In addition, the reduction in rainfall in November was significant and on average 2/43 mm of annual rainfall amount was reduced in this month. In contrast, in September, the amount of precipitation at Ilam station rose. The time series of annual total precipitation received at Ilam station showed that on average 12/57 mm of its rainfall decreased each year. The findings indicated a positive and increasing trend of rainfall in the warm and dry period of the year. While showing a declining trend for most of the other months of the year. Evaluation time index of rainfall showed a greater reduction of rainfall rates in May compared to other months of the year, and on average 2.12 percent of time of rainfall received in this month was reduced every 10 years. However, rainfall times increased by 0.2 and 0.28 percent per decade in September and October, respectively}, keywords = {amount and time of rainfall,Ilam synoptic station}, title_fa = {واکاوی وردایی مقدار و زمان بارش در ایستگاه همدید ایلام}, abstract_fa = {هدف از انجام این پژوهش واکاوی وردایی مقدار و زمان رخداد بارش در ایستگاه همدید ایلام است. در این مطالعه از داده­های روزانه­ی بارش ایستگاه همدید ایلام طی بازه­ی زمانی 1/3/1365 تا 31/6/1391 استفاده شد. همگنی و ناهمگنی داده­های بارش به کمک دو آزمون انحرافات تجمعی و بیشینه­ی و رسلی ارزیابی گردید. معناداری روند داده‌ها به کمک آزمون نا پارامتریک من­کندال محاسبه شد. برای برآورد شیب از تخمینگر شیب سن بهره گرفته شد. سال جهش در سری زمانی مقادیر ماهانه­ی بارش به کمک دو آزمون همگنی یادشده شناسایی شد و معناداری تفاوت در میانگین سری زمانی قبل و بعد از سال جهش به کمک آزمون من­ویتنی ارزیابی شد. یافته­ها نشان داد که مقادیر بارش دریافتی طی ماههای مختلف سال در ایستگاه همدید ایلام ایستا نیست. نوع روند و نرخ تغییرات در ماههای مختلف سال یک اندازه و همسان نیست. در ماههای پربارش ایلام، مقادیر بارش دریافتی روند نزولی و معناداری را از خود نشان می­دهند. درحالی‌که در ماههای کم بارش و خشک، مقدار بارشدریافتی ایلام روند مثبت و افزایشی را نشان می­دهند. نرخ کاهشی مقدار بارش دریافتی ماه اسفند نسبت به سایر ماهها بیشینه است. در ماه اسفند به ازایهر دهه 1/36، فروردین 3/19 و در اردیبهشت 2/12 میلی متر از مقدار بارش کاسته شده است. درمجموع مقدار بارش سالانه در این ایستگاه 57/12 میلی‌متر کاهش‌یافته است همچنین یافته­ها نشان داد که روند زمان بارش­های دریافتی دوره­ی خشک و گرم سال افزایشی است اما زمان بارش دریافتی اغلب ماههای دیگر سال کاهشی است. کاهش زمان بارش در اسفندماه بیش از دو ماه دیگر است. در اردیبهشت‌ماه زمان بارش 12/2 درصد کاهش داشته است؛ اما در شهریورماه 2/0 و مهرماه 28/0 درصد در هر دهه افزایش داشته است.  }, keywords_fa = {زمان و مقدار بارش,ایستگاه همدید ایلام}, url = {https://clima.irimo.ir/article_77186.html}, eprint = {https://clima.irimo.ir/article_77186_edccb3a3df8a945133540c6cd6f03d66.pdf} } @article { author = {Sedaghat, Mehdi and Nazari poor, Hamid}, title = {A New Approach for Definition of Summer Season in Iran}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {77-88}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = {Introduction: The climate of the summer season, dry and low rainfall region of the Middle East, has not been considered by atmosphere scientists for unclear reasons. The claim for the need to update the definition of seasons is due to the fact that the weather conditions are not considered in the meteorological and astronomical definitions. Almost all of the definitions given to identify the characteristics of the summer season follow three physical, dynamic and synthetic approaches. The physical index considers days with an average temperature above threshold as a summer day. Dynamically, more heat transfer in the summer leads to an increase in altitude and a reduction in the pressure of the tropopause. Synoptically, scholars have outlined the beginning of the summer to overcome the Persian trough over the region. In addition, with the sudden disappearance of the Persian trough in the middle of September, the summer season ends. With the assumption that global warming has accelerated the course of the summer period and significantly increased its intensity over the past decades, researchers have been reviewing the summer atmosphere in the Middle East, and especially in Iran, by designing new indicators. Materials and methods, In this study, using the reanalyzed data of temperature, tropopause pressure and geopotential height of the NCEP/NCAR database during 1948-2016, the characteristics of the summer season, including its start, peak, durability and ending in Iran has been evaluated. By using the script written in the GRADS software, the daily values of the data were extracted in the desired ranges. Then, in order to estimate the summer period based on the threshold of each indicator, the daily average of the data was calculated. The thresholds for physical, dynamical and synoptic indicators for estimating the start and end of the summer season and the number of summer days, respectively, were daily temperatures higher than 25 degrees, tropopause pressure less than 120, and geopotential heights less than 50 meters. The transit of daily data values from the threshold and their 10-day continuity indicates the beginning and end of the summer period. Finally, the summer weather variations in Iran were also studied based on the Kendal’s tau tests and the graphically Man-Kendal test. Results and discussion, the results of temperature-based index (physical index) with a threshold of 25 degrees Celsius and a 10-day durability shown that the beginning of the summer season in Iran is 1 June and its end is 27 September. Based on the variations of the tropopause level pressure (dynamic index) with a pressure threshold of less than 120hp and ten day duration, the beginning of the summer season is 4 June and the its end 1 October. The results of the assessment based on the index of geopotential height changes in 1000hp level (Synoptic index; Persian Trough Formation) with a threshold of 50 meters and ten days duration showed the beginning and end of the summer season in the Iranian region, 20 May and 15 September, respectively. The average annual summer season based on physical, dynamic and synoptic indexes was estimated, respectively, 134, 120 and 119 days. The results of trend analysis indicate that the frequency of summer days on the Iran based on the physical index has a significant upward trend. Accordingly, the summer atmosphere has a tendency towards early starters and late end-time. Dynamic and especially Synoptic indices the opposite of the physical index show the declining trend of summer atmosphere. Conclusion, The time series process of the temperature-based physical index indicates the upward trend in the number of summer days during the study period. The correlation coefficient of τ=0.39 and a significant trend in the time series of the mean time average of the summer temperatures of the 69-year period, also proving the hypothesis that climate change was happened. In terms of the physical index (temperature) over the last seven decades, the summer tended to start earlier and more sustained, while the synoptic index was opposite. In contrast, the time series of the synoptically index based on the period of the Persian trough formation over the Persian Gulf region indicates a decline in the number of annual summer days. Because of the differences in the results of the physical index and the similarity of the dynamical and synoptic indexes with previous studies, the authors emphasize the need for further research in this regard.}, keywords = {Physical Index,Dynamical Index,Synoptically Index,Persian Trough}, title_fa = {نگرشی نو در تعیین جو تابستانه ایران}, abstract_fa = {     ادعای نیاز به بروز رسانی تعریف فصول در نتیجه این واقعیت شکل گرفته است که در تعاریف هواشناختی و نجومی شرایط جو واقعی لحاظ نشده‌اند. در این پژوهش با بهره‌گیری از داده‌های بازکاوی شده دما، فشار تروپوپاوز و ارتفاع ژئوپتانسیل پایگاه مرکز ملی پیش بینی محیطی و مرکز ملی تحقیقات جو طی سال‌های 1948 تا 2016، مشخصه‌های زمانی فصل تابستان شامل زمان آغاز، اوج، دوام و پایان آن در گسترده ایران مورد ارزیابی قرار گرفته است. نتایج بر اساس شاخص مبتنی بر دما(شاخص فیزیکی) با آستانه 25 درجه سلسیوس و دوام 10 روزه، آغاز فصل تابستان در گسترده ایران را 11 خرداد و پایان آن را 5 مهر نشان داده است. بر اساس شاخص مبتنی بر تغییرات فشار سطح تروپوپاوز(شاخص دینامیکی) با آستانه فشار کمتر از 120 هکتوپاسکال و دوام ده روزه، آغاز فصل تابستان 14 خرداد و پایان آن 9 مهر می‌باشد. نتایج ارزیابی بر اساس شاخص مبتنی بر تغییرات ارتفاع ژئوپتانسیل تراز 1000 هکتوپاسکال(شاخص همدید؛ استقرار ناوه پارسی) با آستانه 50 متر و دوام ده روزه نیز آغاز و پایان فصل تابستان در گستره ایران را به ترتیب 30 اردیبهشت و 24 شهریور نشان داد. میانگین سالانه طول دوره فصل تابستان بر اساس شاخص های فیزیکی، دینامیکی و همدیدی، به ترتیب ۱۳۴، ۱۲۰ و ۱۱۹ روز برآورد گردید. تحلیل وردایی‌های زمانی با آزمون‌های تاو کندال و آزمون نموداری من-کندال دنباله‌ای نشان داد که فراوانی روزهای استیلای جو تابستانه بر گستره ایران بر اساس شاخص فیزیکی از روند افزایشی معنی‌دار برخوردار است. بر این اساس جو تابستانه میل بر آغازگری زودتر و پایان‌پذیری دیرتر دارد. ضریب همبستگی تاو 0.39 و روندی افزایشی کاملاً معنادار سری زمانی متوسط میانگین منطقه‌ای دماهای تابستانه دوره 69 ساله بیانگر تغییر اقلیم حرارتی در منطقه است. شاخص های دینامیکی و بویژه همدید برعکس شاخص فیزیکی روند کاهشی استیلای جو تابستانه را نشان می‌دهند.}, keywords_fa = {فصل تابستان,شاخص فیزیکی,شاخص دینامیکی,شاخص همدید,ناوه پارسی}, url = {https://clima.irimo.ir/article_77187.html}, eprint = {https://clima.irimo.ir/article_77187_288c4d123f47437e3eba526577515c0f.pdf} } @article { author = {SHirmohammadi, Zahra and Kouhi, Mansoureh and Mohammadian, Azadeh and Habibi Nokhandan, Majid and Mirzaee, Mohammad Javad and Mododi, Mohammad NAser}, title = {Spatial and temporal characteristics of Refrence evapotranspiration using CRU gridded datasets and prediction of its changes during future periods in Khorasan Razavi}, journal = {Journal of Climate Research}, volume = {1397}, number = {33}, pages = {89-109}, year = {2018}, publisher = {https://www.irimo.ir/}, issn = {2228-5040}, eissn = {2783-395X}, doi = {}, abstract = {Introduction Evapotranspiration is significantly affected by global climatic changes as an essential component of both climate and hydrological cycles. Comprehensive analyses of the spatiotemporal changes of ETo enhance the understanding of hydrological processes and improve water resource management. The main objective of this study are to investigate and predict the temporal trend and  spatial distributions of the reference evapotranspiration (ET0) during 1961-2014, 2021-2050 and 2051-2080 over Razavi Khorasan Province using observed grided dataset named CRU and four GCMs outputs.    Data and methods 2.1. study area Razavi Khorasan Province is located in northeastern Iran.  This province is located within the longitude and latitude of 56° 19” to 61° 16” E and 33° 52” to 37° 42” N. The climate of this area can be characterized as arid and semiarid with a long term annual precipitation of about 207.5 mm and a long term annual maximum and minimum temperture of 18.3°C and 9.3°C , respectivily. 2.2.data Monthly maximum and minimum temperature data were collected from updated highr esolution (0.5°× 0.5°) gridded dataset of CRU initially released in 1999 by New et al., total 42 grid points in Razavi Khorasan province. After assessing the accuracy of the CRU data using 11 synoptic stations over this province, the monthly ETo values were calculated using Hargrives-Samani method to study the spatiotemporal variations in this variable. The impact of climate change on future spatiotemporal Eto, evaluated using four coupled atmosphere-ocean general circulation models (AOGCMs) under RCP8.5 scenarios. The parametric t-test and nonparametric Mann-Kendall test methods were used to analyze the temporal characteristics of annual ET during 1961-2005, 2021-2050 and 2051-2080. Results and Conclusions The results were as follows: (i) generally, ETo increased from north to south across the province (ii) from 1961 to 2014, annual ET exhibited an increasing continuous trend across the area under study (iii) ETo also displayed a significantly increasing temporal trend during two future periods across Razavi Khorasan Province. (v). The difference between mean annual ETo values of two periods was statistically significant in all grid points covering this province. The results showed that these increases may lead to the increase in crop water requirements and aggravate the water shortage in this area in view of the increase in ET0 in response to ongoing climate change.  ETo play an important role in the agricultural and water resources management, and its accurate prediction will signify better planning and management of the water, agriculture and other sectors, hence, using outputs of GCMs can facilitate the sectors by reliably predicting the future climate change impact on ETo in this province.}, keywords = {Climate change,ETo,CRU gridded dataset,Climate model}, title_fa = {بررسی توزیع مکانی-زمانی تبخیر-تعرق مرجع با استفاده از داده‌های شبکه‌بندی CRU و پیش‌نگری تغییرات آن طی دوره‌های آتی در خراسان رضوی}, abstract_fa = {در این پژوهش، نحوه توزیع مکانی-زمانی تبخیر-تعرق محاسبه‌شده با استفاده از داده‌های شبکه‌ای CRU برای استان خراسان رضوی طی دوره 2014- 1961 بررسی‌شده و میزان تغییرات مکانی-زمانی آن طی دو دوره‌ی آینده نزدیک (2050-2021) و میانی (2051-2080) نیز با استفاده از برونداد 4 مدل اقلیمی آرشیو در CMIP5تحت دو سناریوی RCP8.5  و RCP4.5 پیش‌بینی‌شده است. به‌منظور محاسبه مقدار تبخیر-تعرق مرجع، میزان صحت داده‌های دمای کمینه و بیشینه CRU با داده‌های دمای 11 ایستگاه همدید استان مقایسه گردید. بر اساس معیارها و نمودارهای آماری، همخوانی مناسبی بین داده‌های شبکه با داده‌های ایستگاهی در اکثر ایستگاه‌های این استان وجود داشت. بر اساس تبخیر-تعرق محاسبه‌شده، این متغیر در محدوده خراسان رضوی دارای دامنه‌ای از 720تا 980 میلی‌متر در سال می‌باشد. نقشه‌ی ترسیم‌شده نشان داد شیب مکانی در توزیع مقدار EToوجود دارد و با افزایش عرض جغرافیایی از میزان این متغیر کاسته می‌شود. روند زمانی این متغیر طی این دوره برای تمامی نقاط شبکه، معنادار و افزایشی به دست آمد. برای دوره‌های آتی و بر اساس آزمون t، برای تمام نقاط شبکه، تفاوت بین مقادیر میانگین سالانه تبخیر-تعرق دوره پایه با دو دوره آینده، ازنظر آماری معنادار بوده و مقدار میانگین سالانه این متغیر طی دو دوره آتی، بیشتر از مقدار آن در دوره پایه می‌باشد. طی آینده نزدیک، بیشترین درصد افزایش این دوره نسبت به دوره پایه، توسط مدل IPSL و CSIRO پیش‌بینی‌شده است. در این 2080-2051، درصد افزایش ETo در چهار مدل بیش از دوره پایه و دوره‌ی آینده نزدیک، پیش‌بینی‌شده است. بالاترین درصد افزایش همانند دوره قبل، برای دو مدل IPSL و CSIRO به‌دست‌آمده است. از نظر الگوی مکانی تحت دو سناریو 5/4 و 5/8، سه مدل GFDL، CCSM4 و CSIRO بیشترین افزایش را در قسمت شمال غرب استان نشان می‌دهند درحالی‌که در مدل IPSL، مرکز و نیمه شرقی استان احتمالا شاهد بیشترین درصد افزایش تبخیر-تعرق مرجع نسبت به دوره پایه خواهد بود.}, keywords_fa = {تغییر اقلیم,تبخیر-تعرق,داده‌های شبکه‌ای CRU,مدل اقلیمی}, url = {https://clima.irimo.ir/article_77189.html}, eprint = {https://clima.irimo.ir/article_77189_98c41b15651d656dec918ae9e60e8627.pdf} }