@article { author = {Karimi, Alireza and Khademi, H and Jalalian, A}, title = {Loess: Characteristics and Implications in Paleoclimate Studies}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {1-20}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Loess studies have about 185 years of documented history. High agricultural suitability, sensitivity to erosion and archiving the climatic changes signals, make the loess deposits very interesting to study. Understanding the historical development and different aspects of loess sediments are necessary for further investigations on loess deposits. Methodology Regarding the published studies on loess, this paper has been organized into five sections including: 1) definition and characteristics of loess, 2) history of world loess studies, 3) processes of silt production, 4) importance of loess deposits for paleoclimate studies and 5) investigations carried out on Iranian loess deposits and soils. Major references for each subject were reviewed. Results and Discussion The word "loess" has been derived from the German word "L?s", meaning loose, which was used for the first time by Leonhard in 1824. Regarding the definitions of loess presented by many authors, aeolian origin and silt fraction dominance have been accepted as the two main characteristics of loess deposits. The particle size distribution is the most important characteristic, which is measured before any other properties. The common mineralogical composition of loess deposits is as fallows: quartz in the sand fraction and quartz, feldspars, carbonates, mica and heavy minerals in the silt fractions. Illite and smectite are dominant minerals in clay fraction. However, the mineral composition is highly related to the loess origin. For example, loess in Argentina contains a lot of glass and feldspars, while Spanish loess deposits contain anhydrite and gypsum because they have originated from volcanic ash and Tertiary formations, respectively. Furthermore, soil formation processes during interglacial periods might have caused mineral transformation. Loess was first identified by Leonhard in 1824. Lyell in 1833 attracted a lot of attention to loess deposits worldwide through his several reports. Determining the nature (aeoloan, alluvial or in situ genesis) and clarification of silt formation processes have been two main research subjects during this period. Berg (1916) suggested the in situ formation of loess; but Richtofen in 1882, many years before Berg, had proven the aeolian origin of loess deposits. Based on the close relationship between the major loess deposits areas and ice sheet regions, Tutkovskii in 1899 explained the role of glaciers in silt production. Even until recent decades, some researchers such as Smalley believed that glacial grinding was the main process having enough energy to produce quartz silt. Obruchev in 1945 divided loess into hot and cold loess and referred to factors except glacial grinding for silt production. Currently, based on the silt origin, loess deposits are grouped into four classes including glacial or periglacial loess, desert or peridesert loess, mountain or perimountain loess and non-typic loess. Quartz silt is the most common particle in loess deposits. In the early studies, much attention was paid to the close relation between extensive loess deposits and glacial and periglacial paleoenvironments, giving rise to the hypothesis that glacial grinding was the main silt generating mechanism. Identification of loess deposits in desert environments showed that there were mechanisms other than glacial grinding for quartz comminution. Salt weathering, frost weathering, aeolian abrasion, and fluvial comminution are responsible mechanisms for silt production. Nahon and Trompette (1982), Wright (2001) and Iriondo and Kr?hling (2007) believe that, on a global scale, the importance of glacial grinding for the production of silt is less than what was initially expected. The other important aspect of loess studies is based on the observations of Hardcastle in 1890 who related loess formation to climate changes. Up to now, research reports have shown that loess deposition and soil formation were active during the cold glacial and hot interglacial periods, respectively. The periods of loess deposition and soil formation are well correlated to marine isotope stages. This finding is the basis for paleoclimate reconstruction and landscape evolution. There are vast areas covered by loess deposits in northern Iran. The presence of loess deposits in other parts of the country, especially desert fringes, is expected. For example, loess deposits in southern Mashhad and in Persepolis basin have been recently identified. It is evident that the loess thickness in dry regions is much less than that in the north. In recent decade, diverse aspects of loess deposits from northern and other parts of the country have been studied. The results of these studies showed the overall correlation of loess deposition and soil formation between Iran and major loess areas of the world during last glacial-interglacial period. The most important findings are windy LGM (MIS2) and soil formation during MIS5. There are, however, many unknowns, which should be clarified in the future investigations. Conclusion Loess is an aeolian silt-dominant sediment. Although it is believed that quartz and mica are the main mineral constituents, however, the mineral composition is highly related to the loess origin. Loess accumulation is a climate dependent phenomenon. The common argument is that loess deposition and soil formation were active during the cold glacial and hot interglacial periods, respectively. This fact makes the loess-peleosol sequences as a reliable archive of climate changes. The loess studies in Iran are limited and it is necessary to determine the loess distribution around the country and investigate their physical, chemical and mineralogical characteristics as well as their implication for paleoclimate studies.}, keywords = {loess,Marin isotope stages,paleoclimate,Paleosol,Silt}, title_fa = {لس: ویژگی‌ها و کاربردها برای مطالعات اقلیم گذشته}, abstract_fa = {مطالعات مستند لس، قدمت 185 ساله دارد. بادرفتی‎بودن و غالب‎بودن جزء سیلت، دو ویژگی اصلی رسوبات لسی است. لئونارد در سال 1824 این رسوبات را شناسایی و واژه‎ی لس را برای آنها ارائه کرد. لایل در سال 1833 با گزارش‌های خود، توجّه جهانی را به این رسوبات جلب کرد. تعیین ماهیّت (بادرفتی، آبرفتی یا تشکیل درجا) و تعیین و تبیین فرآیند‌های تولید سیلت، دو موضوع مهم پژوهش‌ها در این دوره بوده‌اند. برگ (1916) به‎شدّت طرفدار تشکیل درجای لس بود، ولی ریکتوفن، خیلی پیش‌تر از او، در سال 1882، ماهیّت بادرفتی رسوبات لسی را اثبات کرده بود. تاتکوفسکی در سال 1899، بر اساس رابطه نزدیک پهنه‌های بزرگ لسی با نواحی یخچالی، نقش یخچال‌ها را در تولید سیلت مطرح کرد و حتّی تا دهه‎ی اخیر، برخی پژوهشگران مانند اسمالی با آن موافق بوده و سایش یخچالی را تنها عامل دارای انرژی کافی برای تولید سیلت کوارتزی می‌دانستند. ابرشو در ابتدای قرن بیستم (1911)، لس را به دو دسته‎ی لس سرد و لس داغ یا بیابانی، تقسیم و به عواملی غیر از سایش یخچالی برای تولید سیلت اشاره کرد. در حال حاضر بر اساس منشأ سیلت، رسوبات لسی به چهار دسته‎ی لس یخچالی یا حاشیه‎ی یخچالی، لس بیابانی یا حاشیه‎ی بیابانی، لس کوهستانی یا حاشیه‎ی کوهستانی و لس غیر تیپیک تقسیم شده‌اند. جنبه‎ی دیگر مطالعات لسی بر اساس مشاهده‎های اولیه هارد کاستل در سال 1890 بود که تشکیل لس را به تغییرات اقلیمی ربط داد. نتیجه‎ی مطالعات فراوان تا به امروز، نشان داده است که رسوب لس و تشکیل خاک، به‌ترتیب در دوره‌های سرد یخچالی و گرم بین‌یخچالی انجام شده است. در ایران پهنه‌های گسترده‎ی لس در شمال کشور وجود دارد. در دهه‎ی اخیر، مطالعات گسترده‌ای درباره‎ی جنبه‌های مختلف رسوبات لسی در قسمت‌های مختلف ایران انجام شده است؛ با این حال، هنوز نیاز به بررسی‎های بیشتر احساس می‌شود. در این نوشتار، پژوهش‎هایی که در دنیا درباره‎ی لس‎ها انجام‎شده مورد بررسی قرار گرفته و تاریخچه‎ی مطالعات لس در ایران تشریح می‌گردد.}, keywords_fa = {loess,Marin isotope stages,paleoclimate,Paleosol,Silt}, url = {https://jphgr.ut.ac.ir/article_23067.html}, eprint = {https://jphgr.ut.ac.ir/article_23067_baf49409ff2061e1757d9e50e5a4a11b.pdf} } @article { author = {farajzadeh, manochehr and Khoorani, A and Bazgeer, S and Zeaeian, P}, title = {Modeling and Predicting of Rainfed Wheat Yield in Attention to Phenological Phases of Plant Growth (A Case Study for Kurdistan Province)}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {21-34}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Agricultural production is affected by risks originated from weather and international markets. Although these risks could never completely been removed, we can minimize their effects by realizing the effective parameters in plant growth and crop yield and consequently by estimating the crop yield amount. Among these parameters, climate has a more significant role, especially in rainfed crops. Rainfed wheat is one of the major agricultural crops in Kurdistan province that includes most of the cultivated area. In 2006, Kurdistan province had %11.8 of the cultivated area which encompasses %13.67 of the rainfed wheat yield of the country. Regarding environmental outcomes, quite good prediction may be acquired by empirical fits of these crop-yield weather regression type models to real datasets. The aim of this paper is achieving higher accuracy revealed statistical models for rainfed wheat yield in different plant growth stages, regarding weather parameters and some specific agrometeorological indices. It is noticeable that non-weather parameters such as economic and management consideration to rainfed wheat yield were not considered in this study. Methodology Therefore, in this study the prediction of rainfed wheat yield in Kurdistan province has been carried out, based on agrometeorological indices and climatological parameters. For this purpose Ranifed wheat yield data for Kurdistan province (34: 44? to 36:30? N? to 45:31? to 48:16?E) as well as its counties include Bijar, Sanandaj, Saghez, Ghorveh, Marivan and Divandareh, were obtained from Iran Aagriculture Ministry and also necessary weather parameters were obtained for all the weather stations in Kurdistan province from Iranian National Meteorological Organization for the period 1991-2006 (1993-2006 for Marivan station). Correlation and nearest neighboring methods were used for filling the missing data. Then linear stepwise regression models were developed for rainfed wheat yield data and independent parameters during 1991- 2003 years (1993-2003 for Marivan station). Stepwise regression method was chosen due to high amount of the independent parameters. The independent parameters in this study are 5 agrometeorological indices include; Growing Degree Days (GDD), Heliothermal Units (HTU), Photothermal Units (PTU), Vapor pressure deficit (VPD), Temperature Differences (TD) and 12 climatological parameters include; average maximum (Tmax) and minimum temperature (Tmin), absolute maximum (Tabs(max)) and minimum temperature (Tabs(min)), average (FF) and absolute (FFabs(max)) wind speed, relative humidity (RH), total (PET(total)) and average evapotranspiration (PET), sunshine hours (SH), total precipitation (R), rainy days (R(day)). Each daily amount of hese parameters has been extracted for six phenological phases of plant growing season from sowing to harvest. These stages are; the first stage of active vegetative before dormancy stage from November 7th to December 11th, dormancy stage from December 12th to March 15th, the second stage of active vegetative after dormancy stage from March 16th to May 10th, reproductive stage from May 11th to June 9th and maturity stage from June 10thto July 10th. In order to obtain the best models, regression models were calibrated for each rainfed wheat yield stage as well as the entire growing Season and that of the start of second stage of active vegetative after dormancy stage to the end of reproductive stage from March 16th to June 9th. Thus, 8 regression models were calculated for each study area. After entering The independent parameters in stepwise regression models the predictive parameters were chosen for each station and each phenological phase and based on R, R2, and SEOE the best models were chosen. Then crop yield for 2003-2006 is estimated, accordingly. Results and Discussion The developed models show that 81, 70.2, 82.2, 71, 80, 90.6 and 65.6 percent of wheat yield variations is due to climatological parameters and agrometeorological indices for Baneh, Marivan, Divandareh, Bijar, Ghorveh, Saghez and Sanandaj provinces, respectively. In addition, the best phenological phase for predicting wheat yield for Bijar, Ghorveh, Saghez provinces are reproductive stage(May 11th to June 9th), for Baneh province is the second stage of active vegetative after dormancy phase(March 16th to May10th) and for Marivan is the dormancy phase (December 12th to March15th). For Sanandaj and Divandare district regression models are developed by using the data of all the growing season. Conclusion Based on developed regression models for Kurdistan provinde in this study and the comparesion between these models and previous studies, it is obvious that with a combination of climatological parameters and agrometeorological indices and using stepwise regression models can predict higher amounts of rainfed wheat yield variation.}, keywords = {Agrometeorological indices,Rainfed wheat yield predicting,Statistical models}, title_fa = {مدل‎سازی و پیش بینی عملکرد گندم دیم با توجّه به دوره های فنولوژیکی رشد گیاه (مطالعه‎ی موردی: استان کردستان)}, abstract_fa = {این مطالعه، به‎منظور مدل‎سازی آماری و پیش‌بینی عملکرد محصول گندم دیم در استان کردستان، برمبنای شاخص‎های هواشناسی کشاورزی و پارامترهای اقلیمی انجام شده است. به این منظور مدل رگرسیون خطی داده‌های عملکرد محصول گندم دیم، برای سال‎های 70 تا 1382 محاسبه شد. متغیّرهای مستقل در این مطالعه، شامل 5 شاخص هواشناسی کشاورزی و 12 پارامتر اقلیمی هستند که هرکدام برای 6 مرحله‎ی فنولوژیکی رشد محصول ـ از کاشت تا برداشت ـ کل فصل رشد و نیز مجموع مرحله‎ی دوم رویشی پس از خواب و مرحله‎ی زایشی استخراج شده‌اند (در مجموع 8 مرحله از رشد گیاه). با توجّه به زیاد بودن متغیّرهای مستقل،‌ این متغیّرها به‎روش گام‎به‎گام (stepwise) وارد مدل رگرسیونی شده و بهترین متغیّرهای مستقل پیش‌بینی‎کننده برای هر مرحله و هر ایستگاه با توجّه به مقادیر ضریب تعیین (R2)، R، و خطای معیار (SEOE) انتخاب شد‌ند‌؛ سپس از بین مدل‌های ارائه شده برای مراحل رشد، بهترین مدل برای هر شهرستان و کلّ استان انتخاب شد و برای آزمون آنها اقدام به تخمین محصول برای سال‎های 83 تا 1385، با این مدل‎های بهینه شد. نتایج حاصل از این مدل‎ها نشان می‌دهند که 81 ، 2/70 ، 2/82 ، 71، 80 ، 6/90 ، 6/65 درصد تغییرات عملکرد محصول گندم دیم، به‎ترتیب در شهرستان‎های بانه، مریوان، دیواندره، بیجار، قروه، سقز، سنندج با پارامترهای اقلیمی و شاخص‎های هواشناسی کشاورزی استخراج شده، انجام می‌شود. همچنین بهترین مرحله‎ی فنولوژیکی برای پیش‌بینی عملکرد گندم دیم در شهرستان‎های سقز، قروه و بیجار، مرحله‎ی زایشی (22 اردیبهشت تا 20 خرداد) است. این زمان برای شهرستان بانه، مرحله‎ی دوم رشد رویشی پس از مرحله‎ی خواب (26اسفند تا 21 اردیبهشت) و برای شهرستان مریوان مرحله‎ی خواب (22 آذر تا 25 اسفند) است. برای شهرستان‎های سنندج و دیواندره بهترین مدل رگرسیونی با استفاده از داده‌های کل فصل رشد انتخاب شد.}, keywords_fa = {Agrometeorological indices,Rainfed wheat yield predicting,Statistical models}, url = {https://jphgr.ut.ac.ir/article_23068.html}, eprint = {https://jphgr.ut.ac.ir/article_23068_e4aabb94cc9728fe7d8637bde62d9fc0.pdf} } @article { author = {yamani, mojtaba and Shamsipour, Ali and Jafari Aghdam, M}, title = {Renovation of Pleistocene Snow Line on Jajroud Basin}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {35-50}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Since determining climate zones in the mountainous areas are considered as height levels, so researchers have more attention to get height numbers that identifies a special border of different agents erosion control. That is why, for studying development of mountainous areas, reason for studying evolution mountainous areas, researchers are trying to determine the snow line in glacier and preglacier. Jens Esmark and Jean de Charpentier (1824) for the first time have studied in basis of early discoverage and spread out the subject, which glaciers were covered a vast area of land surfaces in the past. In Iran often researchers for evaluate and simulate of quaternary climate, attentions to glaciers evidences and snowlines, biologic evidences and playa and lakes traces. The present survey with the symbolic identity is a struggle for analysis the connection between the directions of unevenness and the development of glacier cirques and at last the determination of quaternary snow line which at the present exist in the area of Jajroud basin. Methodology To this end, descriptive statistics in order to evaluate theoretical theory background of research field visits to prepare images and to control data map base and finally analytical technique has been used. According to the research goal and to achieve the desired results, areas cirque form maps, temperature and precipitation datas as the main variables of the area in determining Snow lines have been analyzed and evaluated. In this regard, the statistics of 52 stations have been used. Considering the correlation between elements of temperature, precipitation and high temperature and precipitation maps of past and present of the area was drawn. By using topographic maps, aerial and satellite photographs, field visits, the use of GPS to determine position of the cirques and about expanding morain, glacier shapes of area (with emphasis on the glacier cirques) was identified. Among the styles of quintuple Porter in order for of optimum Equilibrium-line Altitudes (ELA) and the study Cirque – Floor Method has been used, because according to Porter, the glacier that only fills the cirques its steady-state ELA typically lies not far above the average altitude of the cirque floor (CF). So using this suitable method (the study Cirque – Floor Method) is to determine the height of equilibrium line altitude in the past(Porter, 2001, 1068). From the wright method for assessing the limitation of snow line of the last period of glacier has been used. In this method by determining the site of small cirques and passing 60 percent line of them permanent snow linw is determined. In order to survey the coordination between the spread and development of the area cirques with the direction of uneven nesses, from the Chi – Square Test ( square of X) has been used. Results and Discussion Results indicate that the existences of a connection between the unevenness directions and the spread of cirques in the area have been used. In from that 38.8 present of the area cirques towards the pole and 24.7 present of the cirques in the direction towards equator have been placed. Studies show that the average height of the glacier circus floor in Jajroud basin, 3061 meters and the amount of fashion or view is 3072 meters. posing Average for Circus of poles equal to 3355 m and for the circus of the equator equal to 3567 meters. Also the determinations of the snow line with the use of Porter method at the height of 3072 meters and the use by the method of Wright at the height of 3095 meters have been shown. comparing obtained results with previous researchers comments shows that Schweizer the border of permanent snow now is now southern of Alborz approximately 4400 meters in the northern slopes of Alborz be calculated at about 4200 meters, in findings of Dreschand bobek the permanent snow line already in the Alborz from 4000 to 4200 m and in cold periods is of 3400 to 3600 meters. Zamani the snow line in the Alborz in the last glacier period using the Porter Model in 2748 meters height and using Wrights models is in the height of 2720 meters. also Eyvazi calculated The snow line in the southern Alborz range, in 4400 meters height. Conclusion Comparing obtained results with previous researchers comments shows that Schweizer the border of permanent snow now is now southern of Alborz approximately 4400 meters in the northern slopes of Alborz be calculated at about 4200 meters, in findings of Dresch and bobek the permanent snow line already in the Alborz from 4000 to 4200 m and in cold periods is of 3400 to 3600 meters. Zamani the snow line in the Alborz in the last glacier period using the Porter Model in 2748 meters height and using Wrights models is in the height of 2720 meters. Also Eyvazi calculated the snow line in the southern Alborz range, in 4400 meters height.}, keywords = {climate change,Jajroud basin,Mountain glacier,Quaternary,snowline}, title_fa = {بازسازی برف مرزهای پلیوستوسن در حوضه‎ی جاجرود}, abstract_fa = {پژوهش حاضر با ماهیّت بنیادی، تلاش دارد تا رابطه‎ی میان جهت ناهمواری‌ها و گسترش سیرک‎های یخچالی را بررسی و سرانجام برف‌مرزهای آخرین دوره‎ی یخچالی کواترنری را در حوضه‎ی آبریز جاجرود تعیین کند. سیرک‌ها، جریان‌های یخرفتی و سنگ‌های سرگردان مهم‎ترین لندفرم‌های یخچالی و شواهد تغییرات اقلیمی موجود در حوضه‎ی مورد مطالعه به‎شمار می‌روند. نقشه‌های توپوگرافی، زمین‎شناسی، تصاویر ماهواره‎ای ETM+ و داده‌های اقلیمی دما و بارش ماهانه، ابزارها و داده‌های مورد استفاده در این پژوهش هستند. همچنین از نرم‌افزار Arc GIS 9.3 و سایر نرم‌افزارها برای تجزیه‎وتحلیل داده‌ها استفاده شده است. در این راستا، با استفاده از تصاویر ماهواره‎ای و بازدیدهای میدانی، موقعیّت سیرک‌های منطقه شناسایی‎شده و برای بازسازی خطّ تعادل برف و یخ گذشته (ELA)، از میان روش‌های پنج‌گانه پورتر، روش مطالعه‎ی ارتفاع کف سیرک و از روش رایت نیز برای برآورد حدّ برف‌مرز آخرین دوره‎ی یخچالی استفاده شده است. برای بررسی وجود رابطه میان گسترش و پراکندگی سیرک‌های منطقه با جهت ناهمواری‌ها، از آزمون توان دوم کی پیرسون (مجذور X) استفاده شده است. نتایج نشان می‌دهد که 8/38 درصد از سیرک‌های منطقه رو به قطب و 7/24 درصد سیرک‌ها در دامنه‌های رو به استوا شکل گرفته‌اند؛ همچنین خطّ برف‌مرز وورم با استفاده از روش پورتر، ارتفاع 3072 متر و با استفاده از روش رایت، ارتفاع 3095 متری را نشان می‎دهد. برف‎مرز کنونی با استفاده از داده‌های دما و بارش، ارتفاع 3720 متری را نشان می‎دهد، درحالی‎که بیشتر پژوهشگران قبلی این مرز را بالای 4000 متر تعیین کردند.}, keywords_fa = {climate change,Jajroud basin,Mountain glacier,Quaternary,snowline}, url = {https://jphgr.ut.ac.ir/article_23069.html}, eprint = {https://jphgr.ut.ac.ir/article_23069_4a1b42cad1cabb8b3721679871e88b36.pdf} } @article { author = {Bahrami, Sh and maghsoudi, mehran and Bahrami, K}, title = {Evaluating the Effect of Tectonic in Anomaly of Drainage System Morphometry in Four Catchments in Zagros}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {51-70}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Studied catchments are parts of Zagros belt which is part of the Arabia–Eurasia collision zone. Zagros is an example of a young and active orogenic belt and geomorphic, geologic and seismic evidences reveal that uplifting is migrating from northeast towards the southwest. Among geomorphological evidence of active tectonics, drainage systems and their characteristics like drainage pattern, drainage anomaly, confluence angle of drainages and river direction play an important role in identifying active tectonics and their Spatial variations. In this study, with the aim of evaluation of effect of tectonic on drainage system anomaly, four catchments, Patagh, Piran, Kamandan and Daretakht have been studied. Patagh and Piran are located in Zagros Folded Belt and two other catchments are located in Zagros Thrust Belt. General characteristics of catchments like drainage divide and topography were extracted from topographic maps at a scale of 1:50000. Geological units and their areas were derived from 1:250000-scale geological maps. Methodology Hierarchical anomaly index (?a), Bifurcation index (R), asymmetry factor (AF), transverse topographic symmetry factor (T) and drainage pattern are studied parameters in this research. For calculating mention factors, at first, 20 meter topographic contour lines of catchments have been digitized in the ILWIS (Integrated Land and Water Information System) software and thereby Digital Elevation Model (DEM) and drainage system ordering by Strahler’s method have been prepared. After ordering process, number of channels for all orders was determined. Then, anomalous drainage paths and number of rivers in each anomalous path were achieved. For calculating Hierarchical anomaly index, at first, Ha (minimum number of first order channels which would be necessary to make the drainage network perfectly hierarchized), were calculated for catchments. ?a was calculated as the ratio of Ha divided by the real number of first-order segments of the network. Bifurcation index (R) was calculated as the difference between the bifurcation ratio and the direct bifurcation ratio . of channels with a given order was computed by dividing the number of channels of a given Order by the number of channels of the immediately higher order. Bifurcation ratio of a catchment was achieved by the mean Rb of all stream orders. Direct bifurcation ratio was calculated as: Where represents the number of channels of a given order that flow in channels of the next, higher order, and is the number of channels of the next higher order. The asymmetry factor (AF) was defined as AF=100 (Ar/At), where Ar is the area of the catchment to the right (facing downstream) of the trunk stream, and At is the total area of the catchment. Transverse topographic symmetry factor was calculated as T=Da/Dd, where Da is the distance from the midline of the catchment to the main river, and Dd is the distance from the catchment midline to the catchment divide. Results and Discussion Results of this study shows that the values of hierarchical anomaly index (?a) in Piran and Patagh, in the zone of Folded Zagros, are higher than Kamandan and Daretakht catchments located in the zone of Thrust Zagros. The values of mentioned index in Patagh, Piran, Kamandan and daretakht catchments are 2.06, 1.65, 1.24 and 1.15 respectively. The highest value of Bifurcation index (1.01) is in Patagh and the lowest value (0.75) is in Kamandan catchment. The T values of Patagh, Piran, Kamandan and daretakht catchments are 48%, 39%, 33% and 21% respectively. The values of AF in Patagh, Piran, Kamandan and daretakht are 63, 59, 57 and 56 respectively, indicating that all catchments have been titled towards left. Data analysis reveals that there is meaningful positive relation between ?a and AF so that correlation coefficient (R^2) of these two parameters is 96%. Correlation coefficient between ?a and T is 87%. Nevertheless, studying the relation between R and AF shows that there no positive relation between these two parameters and that their R^2 is 44%. Correlation coefficient between R and T is also weak (23%). Conclusion Studying the drainage pattern of studied catchments illustrates that older and more eroded catchments (Kamandan and Daretakht) in Thrust Zagros have dendritic drainage pattern. Drainage pattern in Patagh and Piran catchments (in younger parts of Folded Zagros) is trellis. However, parallel drainages have developed in steep limbs of anticlines whereas dendritic pattern have established in structural gentle slope. Overall, this research shows that drainage anomaly in studied catchments is affected by tectonics and, that ?a has more performance than R in determining active tectonics of catchments.}, keywords = {Bifurcation Index,Drainage Anomaly,Hierarchical Anomaly Index,Kamanda,Piran}, title_fa = {بررسی نقش تکتونیک در ناهنجاری مورفومتری شبکه‎ی زهکشی در چهار حوضه‎ی آبخیز در زاگرس}, abstract_fa = {این پژوهش، نقش تکتونیک در ناهنجاری سیستم زهکشی در چهار حوضه‎ی زهکشی پیران، پاطاق، کمندان و درّه‎تخت در زاگرس شمال‎غرب را بررسی کرده است. شاخص ناهنجاری سلسله‎مراتبی (?a)، شاخص انشعابات (R)، شاخص عدم تقارن حوضه (AF)، شاخص تقارن توپوگرافی عرضی حوضه (T) و الگوی زهکشی پارامترهای مورد بررسی این پژوهش هستند. پارامترهای مذکور، بر اساس نقشه‎های توپوگرافی با مقیاس 50000/1 به‎دست آمد. خطوط منحنی میزان، با اختلاف ارتفاع 20 متر حوضه‎ها در محیط نرم‎افزار ILWIS رقومی شد و بر اساس آن، نقشه‎ی مدل ارتفاعی رقومی حوضه‎ها و شبکه‌های زهکشی با درجه‎های مختلف به‎روش استراهلر تهیه شد. بعد از تعیین مسیرهای زهکشی ناهنجار و تعداد آبراهه‎ها در هر مسیر، شاخص‎های ناهنجاری زهکشی برای حوضه‎ها تعیین شد. شاخص‎های عدم تقارن حوضه (AF) و شاخص تقارن توپوگرافی عرضی حوضه (T) بر اساس تعیین خط مرکز حوضه‎ها و رودخانه‌های اصلی حوضه‎ها محاسبه شدند. نتایج این پژوهش نشان می‌دهد که مقدار شاخص ناهنجاری سلسله‎مراتبی (?a) در حوضه‎ی پاطاق و پیران که در زاگرس چین‎خورده قرار دارند، نسبت به دو حوضه‎ی دیگر در زاگرس رورانده، بیشتر است. شاخص مذکور در حوضه‎های پاطاق، پیران، کمندان و درّه‎تخت به‎ترتیب 06/2 ، 65/1، 24/1، 15/1 است. حداکثر پارامتر R (شاخص انشعابات) نیز در حوضه‎ی پاطاق (01/1) و حداقل آن در حوضه‎ی کمندان (75/0) است. بررسی داده‎ها نشان می‎دهد، رابطه‎ی معنادار مستقیمی بین پارامتر ?a و AF وجود دارد، به‎طوری‎که ضریب همبستگی بین این دو متغیّر 96 درصد است. ضریب همبستگی بین ?a و T نیز87 درصد است؛ با این وجود، بررسی رابطه بین پارامتر R و AF نشان می‎دهد که رابطه‎ی مستقیمی بین این دو متغیّر وجود ندارد و ضریب همبستگی آنها حدود 44 درصد است. ضریب همبستگی بین R و T نیز ضعیف (23 درصد) است. مطالعه‎ی الگوی زهکشی در حوضه‌ها نشان داد که حوضه‌های قدیمی‌تر و فرسایش‎یافته‌ترِ واقع در زاگرس رورانده (کمندان و درّه‎تخت) الگوی زهکشی شبکه‎ی درختی دارند. الگوی زهکشی کلّی در دو حوضه‎ی پیران و پاطاق (در بخش جوان‎تر و فعّال‎تر زاگرس چین‎خورده) داربستی است، با این وجود، در این حوضه‎ها در پهلوهای پرشیب طاقدیس‎ها، الگوی موازی توسعه یافته است، درحالی‎که در مناطق کم‎شیب ساختمانی‌، الگوی شبکه‎ی درختی دیده می‎شود. به‎طورکلّی، این پژوهش نشان می‎دهد که ناهنجاری زهکشی در حوضه‌های مورد مطالعه، متأثر از تکتونیک بوده و پارامتر ?a، در مقایسه با پارامتر R‌، کارایی بالایی در تعیین تکتونیک فعّال حوضه‎ها دارد.}, keywords_fa = {Bifurcation Index,Drainage Anomaly,Hierarchical Anomaly Index,Kamanda,Piran}, url = {https://jphgr.ut.ac.ir/article_23070.html}, eprint = {https://jphgr.ut.ac.ir/article_23070_5bc2a55278d487d9e432afee415aa1d9.pdf} } @article { author = {zareabayneh, Hamid and Noori, H and Liaghat, A and Noori, H and Karimi, V}, title = {Comparison of Penman- Monteith FAO Method and a Class Pan Evaporation with Lysimeter Measurements in Estimation of Rice Evapotranspiration in Amol Region}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {71-83}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Rice provides more than 80 percent of the calories consumed in a large part of Asia. Rice, in addition to the food, the dependence of the water has unique characteristics. Supplying water requirements of rice, as a plant with high nutritional and economic value is important in many paddy lands. Evapotranspiration for each product such as rice is the ratio of the reference crop evapotranspiration. This ratio is called the crop coefficient that is variable due to the physiological and morphological differences between plant species, and climatic characteristics of the region. With increasing duration of growth, Crop coefficient increases, so that, at crop development, to the maximum and then decreased. In this study, the evapotranspiration of rice plants based on climatic data using pan evaporation and Penman Mantys, compared with the values lysimeter evapotranspiration, was estimated. Methodology This study was conducted during two years of field research and development center to promote technology Haraz at the km 10 Amol - Mahmoud Abad road. In terms of climate, long-term average maximum temperature 32.7 oC, minimum temperature 7.8 oC and mean annual precipitation 882.6 mm that 63 percent of precipitationoccurs in the month of September to December. Two-year field study was performed to investigate paddy rice crop evapotranspiration (ETc) wfor two types of paddy rice variant, Khazar and Tarem, by direct method (lysimeter) and calculated method of FAO in Amol, Mazandaran state. To determine the water requirement and crop coefficient of rice plants, the improved cultivars (Tarom and Khazar) as high yielding varieties during the growing season and crops were compared. All measurements of the water requirements of rice, in machine-based stations Laysymtr Ghyrvzny length 1 m, width 1 m and height was 65 cm. simultaneously reference evapotranspiration (ETo) was estimated by daily measured A class evaporation pan data after calibration of pan coefficient. Calibrated pan coefficients were calculated by different equations such as Cuenca, Allen, Pruitt, Snyder, modified Snyder, Orang and FAO. To determine the accuracy of calculating evapotranspiration rice, measurements of Laysymtry were used. Laysymtry values were used as reference data for comparing the calculated values. Results and Discussion Obtained results by lysimeter showed, rice evapotranspiration in the first and second year of 578.5 (Tarom variety) and 481.6 mm (Khazar variety), respectively. This is due to a higher being during growthof Tarom variety in the first year than Khazar variety in the second year. However, a Tarom variety is long-term with tall plants. Increased during growth, and tall plant height, is effective in the amount of water. The maximum amount of KC in the third stage of rice plant growth, for both years was 1.2. The minimum in the fourth stage, for both first and second years was 0.9. In the present study for both farming year, the value of Kc in the initial stage of growth, was1.09 and 1.13, respectively. Two-year results showed that FAO method overestimate calculated crop evapotranspiration values by 4-5% in comparison of lysimeter measurements. Results showed that Eshnaider method is suitable for ETo estimation of pan coefficient and evaporation pan estimated ETo well in the study region. Estimation of ETc on the basis of pan evaporation data, Eshnyder pan coefficient and FAO modified crop coefficient showed only on the average 1.5% underestimation in comparison with actual ET (ETc). Therefore this method is suitable and practical in the study region. Overall, theresults showed taht using appropriate methods for estimating reference crop evapotranspiration and the crop coefficient, evapotranspiration of rice can be calculated with good accuracy. Applications and is suitable for different regions. Conclusion In this study, due to economic importance and nutritional value of rice in Iran, two-year study to determine the water requirement and select the appropriate method for estimating the evapotranspiration of rice was done. Obtained results by lysimeter showed, rice evapotranspiration in the first and second year of 578.5 and 481.6 mm, respectively. Comparison of rice plant evapotranspiration estimates showed that with an estimate of reference crop evapotranspiration and crop coefficients, the results are closer to the actual value. Among the various methods of estimating pan coefficient, Schneider was more appropriate than other methods. It revealed that, using appropriate methods to estimate reference crop evapotranspiration and crop coefficients applied, can calculated rice evapotranspiration with good accuracy that is applicable and appropriate for different regions.}, keywords = {Amol rice,Crop coefficient & Lysimeter,Pan coefficient,Penman monteith FAO method}, title_fa = {مقایسه‎ی روش پنمن مانتیث فائو و تشت تبخیر کلاس A با داده‌های لایسیمتری در برآورد تبخیر و تعرّق گیاه برنج در منطقه‎ی آمل}, abstract_fa = {در بخش عظیمی از قاره‎ی آسیا، برنج تأمین‎کننده‎ی بیش از 80 درصد کالری مصرفی مردم است. تأمین نیاز آبی برنج، به‎عنوان گیاهی با ارزش غذایی و اقتصادی بالا، در بسیاری از اراضی شالیزاری امری مهم تلقّی می‎شود. در این مطالعه، تبخیر و تعرّق گیاه برنج در قالب طرحی دو ساله، با کشت دو رقم خزر و طارم به دو روش مستقیم (لایسیمتر) و غیرمستقیم (فائو) در منطقه‎ی آمل در استان مازندران مورد بررسی قرار گرفت. در راستای اندازه‌گیری‌های لایسیمتری و محاسبه‎های فوق، تبخیر و تعرّق گیاه مرجع از اندازه‌گیری‌های روزانه‎ی تشت تبخیر کلاس A و تعیین ضرایب اصلاحی تشت تبخیر به‎دست‎آمد. ضرایب اصلاحی تشت تبخیر از معادله‎های پژوهشگران مختلفی مانند کونیکا، آلن و پرویت، اشنایدر، اشنایدر اصلاح شده، اورنگ و کونیکا محاسبه‎شد. با بررسی نتایج لایسیمتری، تبخیر و تعرّق گیاه برنج در سال اوّل کشت 5/578 میلی‌متر و در سال دوم 6/481 میلی‌مترحاصل شد. نتایج مطالعه نشان داد، استفاده از روش پنمن مانتیث فائو در محاسبه‎ی تبخیر و تعرّق گیاه مرجع و اِعمال ضریب گیاهی تبخیر و تعرّق برنج در این منطقه، 5-4 درصد برآورد بیشتری نسبت به مقادیر اندازه‎گیری لایسیمتری دارد. براساس نتایج به‌دست‎آمده، روش اشنایدر برای تعیین ضریب تشت توصیه می‎شود. همچنین، استفاده از تشت تبخیر در برآورد تبخیر و تعرّق گیاه مرجع منطقه‎ی مورد مطالعه، مناسب است. مقایسه‎ی تبخیر و تعرّق برنج برآوردی، براساس داده‌های تشت تبخیر و ضریب تشت اشنایدر و اعمال ضریب گیاهی با مقادیر تبخیر و تعرّق واقعی برنج نشان داد، مقادیر برآوردی به‎طور میانگین 5/1 درصد نسبت به مقادیر واقعی کمتر است که مؤیّد دقّت مناسب مدل در برآورد تبخیر و تعرّق گیاه برنج در منطقه‎ی مورد مطالعه است. در مجموع یافته‌های پژوهش نشان داد با به‎کارگیری روش‌های مناسب تخمین تبخیر و تعرّق گیاه مرجع و اِعمال ضریب گیاهی، می‌توان تبخیر و تعرّق گیاه برنج را که برای مناطق مختلف کاربردی و مناسب است با دقّت مطلوب محاسبه‎کرد.}, keywords_fa = {Amol rice,Crop coefficient & Lysimeter,Pan coefficient,Penman monteith FAO method}, url = {https://jphgr.ut.ac.ir/article_23071.html}, eprint = {https://jphgr.ut.ac.ir/article_23071_8989d2eb8a345c57fe5703cddcd3f66a.pdf} } @article { author = {Omidvar, K and Nekoonam, Z}, title = {An Application of Wind Rose and Dust Rose in the Analysis of Dust Phenomenon and Determining the Seasonal Regime of Dust Winds (Case Study: Sabzevar City)}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {85-104}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Earning easy, fast and applied methods for analysis anemometric data is an essential need for climatology until recognition regime of dust winds. Sabzevar City in Northeast of Iran is a suitable region for continual formation of Dust Phenomenon. These phenomena can have short term and long term harmful effects in this areas. Of course long term effects are a lot more harmful that short term ones. In Sabzevar, precipitation is below of 200 mm and its climate is arid. This phenomenon were taged life and financial damages in Sabzevar. Methodology In this study, dust phenomenon was studied in terms of time and space. Therefore, data involving time and date for supervision, wind direction and speed and current condition of Sabzevar during twenty years statistical period in 1989-2008 were prepared and using these data, statistical analysis about time frequency of dust phenomenon was done in this town. Also, we separately calculated frequency of meteorological codes of Dust phenomenon (06, 07, 08, 09 and 30, 31, 32, 33, 34, 35). we used "WRplot View" software and convert data to appropriate forming for this software and using "paint" software. we draw those in 16 directions and 9 speed classes. Then "Dust Rose" diagram was drawn annually and seasonally and compared with annual and seasonal wind rose in this region. Also, annual Dust Rose was drawn for two codes contain 06 and 07 that they had the most frequency between all data. Results and Discussion The average occurrence of days with dust is 17.15 days in a year and dust days during said statistical period had an increased trend. Also this phenomenon more occur in spring and summer and specific in afternoon. And code 07 appropriated itself more than 90 percent daily reports of Dust phenomenon in Sabzevar station. The study of annual wind rose in Sabzevar synoptic station during statistical period 1989-2008 showed that the average wind speed was 3 m/s and had the most frequency according to speed 3 - 4 m/s. however, measurement of average speed 8.75 m/s for winds with dust of which 43% have a speed more than 10m/s, show that in some occasions in a year, condition is provided for blowing strong winds in a region. The study of seasonal wind roses show that summer season is the most windiest season and only in 20.9 percent of times, weather is quiet and the average wind speed in this season is more than other seasons (3.72 m/s). In addition, the study of seasonal dust roses show that in 77.7 % of times, dust phenomenon is occurred during warm period in a year and winds with a speed more than 10 m/s have the most frequency and spring season with 46.2 % has the most hour report for dust phenomenon. Conclusion According to annual wind rose diagram, in 73.75 % of all wind blow times in this region during twenty year statistical period, wind blow direction is from eastern north to eastern south in this town and in 11.65 % of times, it include western south to western north, and only in 14.6 %, wind blows from other direction towards this town. That is, in 85.4% of all times, wind blows in east-west direction. This result is wholly consistent with topography condition in this town and it seems that wind is channelized in this town in east-west direction. The study of seasonal dust roses results show that in a year, different atmospheric systems make dust phenomena in a region. Starting a cold period in a year, dust winds blow severely from west half of this town and maximize in winter. But with beginning of spring season and western systems recession, these winds blow less from west half towards this town so that they reach to about zero in summer and wholly blow from east half towards this region. As a result, according to Sabzevar topography and wind channelization in east-west direction and the presence of vast regions fit for wind erosion in major wind path in this town as well as the average speed calculation 8.75 m/s for dusty winds, it seems that thiese cases fit condition for formation and severity dust phenomenon and cause dust problem in this town.}, keywords = {Dust,Dust rose,Sabzevar city,Wind regime,wind rose}, title_fa = {کاربرد گلباد و گل‎غبار در تحلیل پدیده‎ی گردوخاک و تعیین رژیم فصلی بادهای همراه با این پدیده (مطالعه‎ی موردی: شهر سبزوار)}, abstract_fa = {یکی از نیازهای اساسی اقلیم‎شناسی، دستیابی به‎روش‎های آسان، سریع و کاربردی تحلیل داده‎های بادسنجی، به‎منظور شناخت رژیم وزش بادهای همراه با گردوخاک، است. پدیده‎ی گردوخاک در سبزوار به‎عنوان یک معضل جوّی در طیِّ سال به‎طور دائـم روی می‎دهد. در این پژوهش، پدیده‎ی گردوخاک از نظر زمانی و فضایی، مورد مطالعه قرار گرفت. بدین منظور داده‎های شامل زمان و تاریخ دیده‎بانی، سمت و سرعت باد و وضعیّت هوای حاضر ایستگاه سینوپتیک سبزوار، طیِّ دوره‎ی آماری بیست‎ساله (1367-1387) تهیّه شد. نتایج حاصل از تحلیل آماری و تحلیل فضایی داده‎ها با استفاده از نرم‎افزار View WRplot (رسم گلباد و گل‎غبار به‎صورت سالانه و فصلی) نشان می‎دهد، به‎طور متوسّط 15/17 روز در سال هوا همراه با گردوخاک است و در دوره‎ی آماری ذکرشده وقوع این پدیده، روند افزایشی داشته است. همچنین، در شهر سبزوار، فصل بهار، شایع‎ترین زمان بروز پدیده‎ی گردوخاک است. بررسی گلباد و گل‎غبار سالانه نیز، تشکیل کانال باد را در مسیر شرقی ـ غربی تأیید می‎کند که کاملاً با وضعیّت توپوگرافی منطقه سازگار است. گل‎غبارهای سالانه که به تفکیک دو کُد هواشناسی 06 و 07 ترسیم شدند، مشخّص می‎کند، بادهایی که در اثر تشکیل سیستم‎های حرارتی در دوره‎ی گرم سال از نیمه‎ی شرقی به‎سمت منطقه می‎وزند، در ایجاد گردوخاک‎های محلّی و گردوخاک‎های فرامنطقه‎ای نقش مهمی دارند؛ اما نقش سیستم‎های غربی، در انتقال ذرّات معلق گردوخاک از سرزمین‎های دورتر، پررنگ‎تر است. گل‎غبارهای فصلی نیز، تأثیر سیستم‎های جوّی مختلف را در طیِّ سال در شکل‎گیری پدیده‎ی گردوخاک در منطقه بهتر و دقیق‎تر نشان می‎دهد. با آغاز دوره‎ی سرد سال، وزش بادهای همراه با گردوخاک از نیمه‎ی غربی به‎سمت شهر سبزوار شدّت‎گرفته و در زمستان به بیشترین حدّ خود می‎رسد؛ اما با شروع فصل بهار و عقب‎نشینی سیستم‎های غربی، وزش این بادها از نیمه‎ی غربی کاهش می‎یابد؛ به‎طوری‎که، در فصل تابستان وزش آنها از سمت غرب تقریباً به صفر رسیده و همه از نیمه‎ی شرقی به‎سمت منطقه می‎وزد.}, keywords_fa = {Dust,Dust rose,Sabzevar city,Wind regime,wind rose}, url = {https://jphgr.ut.ac.ir/article_23072.html}, eprint = {https://jphgr.ut.ac.ir/article_23072_edccda43798e1d06f60cdaea1146273c.pdf} } @article { author = {Yarahmadi, D and Mryanji, Z}, title = {The Analysis of Dynamic and Synoptic Patterns of Heavy Rainfall in the South West of Caspian Sea and West of Iran (Case Study: Rainfall on 04/11/ 2004)}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {105-120}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction Understanding mechanisms and atmospheric circulation patterns which act on the heavy rainfalls is very important, especially because such rainfalls can create catastrophic floods causing damage. Various studies have been conducted on the effects of the atmospheric circulation on the rainfall occurrence all over the world some of which are reviewed here. For example, Habtemicheal and Pedgley (1974) conducted a synoptic study of spring rainfalls in Eritrea. Also, Nicholson (1981) studied the relationship between rainfalls with the atmospheric circulation during periods of drought and wetness in West Africa. The synoptic analysis of monthly and seasonal rainfalls along with the atmospheric circulation in Sri Lanka has been done by Suppiah (1987). Dayan, at al. (2001) described the conditions of synoptic systems causing a severe autumn storm over the Middle East. Kutiel at al. (2001) examined air patterns that create dry and wet periods in Turkey. Littmann (2001) identified the East Mediterranean air patterns by using the geographical location of Azores (an important high-pressure system). In Iran, several studies have been performed in this field. The following can be noted. Sabzi Parver (1991) has done a synoptic review of systems that create floods in the southwest of Iran mentioning that the main factor of causing floods and heavy rainfalls in the southwest of Iran is the presence of a deep trough in the upper levels so that the axis of this trough crosses the south of the Red Sea. Najar Salighe (2001) studied the monsoon and Arabian rainfalls related to the summer rainfalls in Iran. Moradi (2001) carried out a synoptic study of floods on 11, Nov., 1996 floods in the central regions of Mazandaran province. He notes in this regard that the main factors causing rainfalls are the high-pressure on the ground surface and the presence of trough at higher levels. Mofidi and Zarin(2004) conducted a synoptic analysis of the effect of Sudanese low pressure systems on floods and heavy rainfalls occurring in Iran. They are noted that the main role to create flooding rainfall is polar vorticity stretching in 50Hp level. Jahanbakhsh and Zolfaghari (2001) investigated the synoptic models of daily rainfalls in the West of Iran. Omidvar's (2007) survey revealed synoptic and thermodynamic rainfall conditions in the occurrence of rainfalls in Shirkoo Region. Azizi and samadi (2007) studied the synoptic model of the floods on 20, Oct. 2003 in Gilan. They note that this flood was caused by the deep trough in the North-East of Europe. Methodology In this study, the dynamic and synoptic conditions of the heavy rainfalls 14/8/83 (4, Nov., 2004) were studied. On this day, at the number of stations in the country a very heavy rainfall has occurred. The highest rate was reported 147 mm by the Astara station, 115 mm in Bandar Anzali, 52 mm in Mehran, etc. Based on the drawn maps for this day, most rainfall occurred in the southwest of the Caspian Sea and then in the west of Iran. To carry out this synoptic and dynamic analysis, first, the data of the temperature, geo-potential height, humidity, wind and sea level pressures in 2004 for all standard levels were derived from the site www.cdc.noaa.gov. Then, a suitable network that can reasonably analyze the events of the meteorological systems was designed using the Grads in which synoptic systems can be shown. Maps were drawn for the same day and the days before and after the rain for a one- week period. Results and Discussion The results of the study showed that on 4, Nov.2004, there were a low-pressure system on the ground, a trough at the middle levels of the atmosphere, and the advection of cold air in the inspected area which were along with the axis of the jet stream in the north of the Caspian Sea. Due to its meridional component of the wind, the role of components related to changes in the vorticity of the horizontal meridional wind led to increasing the horizontal gradient pressure. The horizontal convergence of the temperature caused the vorticity to be positive and this resulted in intensifying the wind’s vertical speed; consequently, the cyclonic component of the wind was reinforced. Intensified baroclinic situation increases Ascending streams, cloud formation and rainfalls. The next day the Baroclinic instability is weaked. This day expanding high-pressure on the Caspian Sea created the force which rise moisture from ground’s surface to high levels and this has been caused high rainfall, especially in the West Caspian Sea. On the fifteenth’s day in the trough and the cold advection disappear in the West of country and this shows that the unstable system in the region has gone and rainfall is finished. Conclusion The results show that during the occurrence of this rainfall there is a high-pressure system with 1030 Hp in the centre is over the Black Sea and North Eastern Europe. Also at 500 and 700 Hp levels a deep trough is formed and extended from the northwest of the Caspian Sea to the eastern of Mediterranean Sea and to the North East of Red Sea. In the northern Black Sea a high ridge is associated with a high-pressure surface. The analysis of wind maps of the 300 hp level demonstrates that jet stream axis is located on the North Caspian Sea. Also in the study area and the East Mediterranean, winds are fractured and their directions in the West of Iran were turned from north-west to south-east. All these features that were described above caused the area to be highly unstable from the point of view dynamical aspects so that this instability extends from the ground surface to high altitudes, which finally leads to intensity in the rainfalls in the South West if Caspian Sea and west if Iran.}, keywords = {convergence,dynamic,Iran,Rainfall,synoptic}, title_fa = {تحلیل الگوی دینامیکی و همدیدی بارش‌های سنگین در جنوب‎غرب خزر و غرب ایران (مطالعه موردی: بارش مورخه 14/8/1383)}, abstract_fa = {برای شناخت بهتر از بارش‌های سنگین یک منطقه، لازم است تا مطالعات کافی از شرایط دینامیکی و همدیدی رخداد بارش در آن منطقه صورت بگیرد. بدین منظور، پژوهش حاضر، به تحلیل دینامیکی و همدیدی بارش سنگین در تاریخ 14/8/1383 که در غرب ایران و جنوب‎غرب دریای خزر رخ داده می‌پردازد. برای انجام این پژوهش، پارامترهای دما، ارتفاع ژئوپتانسیل، رطوبت، باد و فشار سطح دریا در سال 2004 برای تمام سطوح استاندارد تهیه شد؛ سپس شبکه‌ای که بتواند تحلیل قابل قبولی از رخدادهای هواشناسی ارائه بدهد و تا حدّ ممکن سامانه‌های همدیدی در آن نمایان باشد، طرّاحی شد. در مرحله‎ی بعد پارامترهای جوّی بر روی این شبکه، با استفاده از نرم‎افزار گردس کشیده شد. برای بررسی و تحلیل بهتر به‎مدّت یک هفته، نقشه‌های روزهای وقوع، قبل و بعد از بارش ترسیم شد. نتایج نشان می‌دهد که در روز چهاردهم آبان 1383 در جنوب‎غرب خزر سامانه کم‎فشاری در سطح زمین گسترش یافته است. همچنین در این روز، شکل‌گیری ناوه در ترازهای میانی جو و فرارفت هوای سرد نیز مشاهده شده است. محور ناوه‎ی مذکور با محور جت‎باد شمال خزر همراهی دارد. وضعیّت مؤلّفه نصف‌النهاری باد باعث افزایش شیو افقی فشار شده است که خود موجب افزایش همرفت و ایجاد تاوایی مثبت شده است. این شرایط با تشدید سرعت قائم، مؤلّفه‎ی آزمین‌گرد باد را تقویّت کرده است و موجب تشدید ناپایداری کژفشاری و افزایش جریان‎های صعودی ‌گردیده است. وضعیّت همگرایی و تاوایی تراز 500 هکتوپاسکال این روز، نشان‎دهنده‎ی شرایط مساعد جریان‌های صعودی در جنوب‎غرب خزر و نوار مرزی غرب کشور است. سامانه‎ی ناپایدار در روز پانزدهم آبان به‎تدریج در جنوب‎غرب خزر و غرب به‎دلیل از بین‎ رفتن ناوه‎ی مذکور و فرارفت هوای سرد و همچنین غلبه‎ی شرایط واگرایی در سطوح بالای جو و پُرفشاری در سطح زمین، تضعیف و ناپدید می‌شود که این به معنی توقف بارش در این منطقه است.}, keywords_fa = {convergence,dynamic,Iran,Rainfall,synoptic}, url = {https://jphgr.ut.ac.ir/article_23073.html}, eprint = {https://jphgr.ut.ac.ir/article_23073_601a83ac9f0c4b2b9cf191803f184277.pdf} } @article { author = {mozaffari, gholam ali and Azizian, M. S}, title = {A Study about Wheat Sunn Pest Diffusion According Temperature Characteristics in Kordestan Province (Case Study: Bijar Countryship)}, journal = {Physical Geography Research}, volume = {43}, number = {76}, pages = {121-135}, year = {2011}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {}, abstract = {Introduction The sunn pest is main pest of wheat in west Asia and Near East (Afghanistan, Iran, Iraq, lobnan, Syria and Turkey) and in Central Asia Republics (Ghzagestan, Ghergizestan, Tajikistan, Turkmenistan, Uzbekistan) Bulgaria and Romania. It is estimated damage amount of wheat production between 20 and 70 percent. Unless unbattle with sunn pest, damage amount will receive to 100 percent. The pollutant amount of agriculture lands is about 8 million Hectare in the world. The damage amount resulted from pest, and herbs are about 30-35 percent which It is about 10-12 percent is belong to pest. The sunn pest is an important pest of wheat and barley in Iran that damage wheat and barly production each year. The importance of wheat as a main food of Iranian people is not hidden to any one. Kurdistan is the main producer of wheat in the country. Wheat production in this province is similar to any other parts of the country is not safe from sunn pest, and a great amount of wheat produced is spoiled each year. This research, the temperature Characteristics is analyzed, including average, min, max temperature and daily degree-days in different development stages of sunn pest and it’s relations with sunn pest widespread has been studied. Methodology The case study is Bijar country ship where located in north east of Kurdistan Province. It’s area is about 7730 km2 and located in 47 deg and 36 min East longitude and 35 deg and 52 min North latitude. For doing this research, It has been used sunn pest information and climatological elements from 1370-71 to 1381-82. The sunn pest and sunn pest battle level information during this period were collected from the institute center of agriculture Kurdistan and the daily temperature data were taken Bijar Synoptic station. The frost days number were classified in 3 groups, weak frost (0 to -3), medium frost (-3.1 to -5) and hard frost (-5.1 and less). The monthly, seasonally and annually variations of sunn pest battle level were computed. The degree-day amount for 6 centigrade degree in five different times were computed. The correlation coefficient and coefficient of determination R2 were used to analyze the results statistically. Results and Discussion The variation coefficient of sunn pest battle level is high during past 12 years. The sunn pest battle level total were among 52 till 82389 hectares during this period. The sunn pest battle level increase when temperature increases and frost days number decreases. The very low temperatures along with hard frost are caused to kill winter diapauses periods and activity periods sunn pest at field surface. The finding research shows that the degree-days amount for 6 centigrade degree (temperature base for vital sunn pest ) is between 413.8 till 1132.7 degree-days in turn 1375-76 and 1378-79 years. The maximum degree-day amount is relevant 1378-79 year about 1132.7 and the minimum degree-day is about 413.8 degree-day for 1375-76 year. The degree-day amount has been increased from 1377-78 forward. Conclusion The sunn pest density is dependent to temperature situation. When temperature and degree-days are high in the spring and also the total number of yearly frost and hard frost during former autumn and winter is low, sunn pest spreads hard and vice versa, When temperature and degree-days in the spring is low and total number of yearly frost and hard frost during former autumn and winter is high, sunn pest spreads low. There is a non meaningful negative correlation between weak frost, medium frost, hard frost frequency, and total frost number in autumn and winter seasons with sunn pest combat level. The R2 amount was computed equal 0/424 for these elements.Then, the regression analysis was achieved between degree-days yearly amount and degree-days amount during activity sunn pest in field surface with sunn pest combat level. The R2 amount was computed equal 0/703 which It shows the importance of degree-day for forecasting sunn pest uprising. Finally, the regression model was given according such two parameters.}, keywords = {Agricultural climatology,Bijar country ship,Degree-days,Frost,Sunn pest,Wheat}, title_fa = {بررسی طغیان آفتِ سنِ گندم بر مبنای ویژگی‎های دما در استان کردستان (مطالعه‎ی موردی: شهرستان بیجار)}, abstract_fa = {اهمیت گندم به‎عنوان غذای اصلی مردم در کشور برکسی پوشیده نیست. استان کردستان یکی از قطب‌های تولید گندم کشور محسوب می‎شود. محصول گندم این استان نیز، مانند سایر نقاط گندم‎خیز کشور از آفتِ سنِ گندم در امان نبوده و این آفت هر ساله مقادیر زیادی محصول گندم این استان را نابود می‎کند. در این پژوهش، ویژگی‎های دما شامل دماهای میانگین، حداقل، حداکثر و میزان واحدهای گرمایی روزانه در پنج مقطع زمانی و رابطه‎ی آن با میزان گسترش آفتِ سن در طول سال‎های زراعی 71-70 تا 82-81 در سطح شهرستان بیجار مطالعه شد. نتایج پژوهش نشان می‎دهد که آفتِ سنِ گندم از نظر میزان جمعیّت به شرایط دمایی وابسته است؛ در سال‌های زراعی که میزان دما و میزان واحدهای گرمایی در فصل بهار بالا بوده و تعداد روزهای یخبندان سالانه و تعداد روز‎های با یخبندان شدید به‎ویژه در فصول پاییز و زمستان سال قبل کم باشد، آفت به‎شدّت طغیان می‎کند و برعکس. نتایج حاصل از تحلیل همبستگی بین مقادیر سالانه واحد‎های گرمایی و میزان واحدهای گرمایی در دوره‎ی فعّالیّت آفت سن در فصل بهار با سطح مبارزه با آفت سن، یک همبستگی قوی و معنادار در سطح 99 درصد را نشان می‎دهد. ضریب تبیین (R2) به‎دست‎آمده، برای مقادیر سالانه واحد‎های گرمایی و میزان واحدهای گرمایی از زمان ریزش آفت سن در سطح مزارع تا زمان خاتمه‎ی مبارزه با آفت سن، برای شهرستان بیجار 70 درصد محاسبه شد که اهمیت واحدهای گرمایی را در پیش‎بینی آفت سن در مدل رگرسیون نشان می‌دهد.}, keywords_fa = {Agricultural climatology,Bijar country ship,Degree-days,Frost,Sunn pest,Wheat}, url = {https://jphgr.ut.ac.ir/article_23074.html}, eprint = {https://jphgr.ut.ac.ir/article_23074_6e1e24be314248fce6569031ee812618.pdf} }