Climatology
Majid Rezaei Banafsheh; fatemah jafarishandi; Fereshteh Hossien alipour Jazi
Abstract
Introduction In this study, to analyze the effect blocking system on the precipitation during 1379 Sample rain, the weather maps of mean sea level pressure, geopotential height at 500 hpa level, wind components, moisture flux convergence and were analyzed. The data of daily precipitation were analyzed ...
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Introduction In this study, to analyze the effect blocking system on the precipitation during 1379 Sample rain, the weather maps of mean sea level pressure, geopotential height at 500 hpa level, wind components, moisture flux convergence and were analyzed. The data of daily precipitation were analyzed for meteorological stations by using Environmental approachto circulation during 1951 to 2013.The results suggest that three patterns have been effective in a rain storm and the establishment of Scutoff low in the Wast North West Iran and its associated trough displacement and ground accompaniment, which have provided the conditions for the creation of heavy rainfall. Because heavy rainfall is a type of atmospheric anomaly, many researchers are looking at how it occurs in abnormal weather patterns, including blocking patterns and other unusual synoptic patterns. Systems that are cut from the main west turn are called blocking systems (Habibi, 2006: 70). Researchers who have studied blocking systems such as Silman (2008) using the atmospheric-ocean output model, Kumar et al. (2008) using the air forecasting model, Timevios et al. (2010) using the Self Orgnizing Map (SOM), Caspar and Muller (2010) used the clustering method of hierarchy and Hang et al. and Yarahmadi and Marijanji (2011) by studying the low pressure system on the earth's surface, the atmosphere of the mid-atmosphere and the rise of cold weather And Gavidel (2014) have studied blocking system with the occurrence of blocking at 500, 600 and 700 hectopascal levels. Methodology In this study, High-level atmospheric data for rainfall analysis of days that have been rainy for more than 1 day include altitude geopolitical data of 500 HPL (meter potential), Uwind and Vwind (meters per second) and special humidity (grams per kilogram). These data are from 00:00, 06:00, 12:00 and 18:00 Greenwich Mean Time in the range of 0 to 80 degrees north and 0 to 120 degrees east with a spatial resolution of 2.5 × 2.5 degrees. It has been extracted from a database (NCEP / NCAR) affiliated with the United States National Oceanic and Atmospheric Administration. First in the form of an environmental approach to circulation, Rainfall of more than one day in the spring during 62 years of statistics, which is 1379 days, was extracted. From these 1379 rainy days, based on the base index of 99th percentile, precipitation of more than 25.88 mm was selected. Therefore, 58 days of precipitation became the basis for the study of heavy spring rains. Because the purpose of the work is to check the blocking, the period of precipitation should be more than one day to determine the cause of heavy precipitation based on blocking or other systems. Then, using cluster analysis, the clustering of these 58 rainy days was studied. The results showed that three pressure patterns are effective in creating rainfall in Tabriz. For each of the patterns, a representative day with a correlation threshold of 95% was calculated and analyzed. Results and discussion At the time of pressure pattern 1, the Siberian high-pressure range stretched from 45 to 55 degrees north latitude to the west to the northern latitudes of Iran, and with low pressure on Turkey, provided thermal gradient. At the pressure pattern 2, a strong high-pressure nucleus with about 1032 HPL was formed in northern Mongolia. The tabs on this core, along with the high-pressure tabs of Siberia, have created extremely stressful conditions at the site of the low-pressure collision on northwestern Iran and Turkey. At the time of the establishment of the pressure pattern 3, tabs of the high-pressure system of the Scandinavian islands were drawn from the Black Sea to northwestern Iran. On the other hand, the whole of Iran is covered by the low pressure spread by Saudi Arabia. These conditions have led to an increase in the temperature and the provision of fronts and instability in Tabriz. In this way, the heavy rainfall that can be seen in the depths of the heart of this instability can be justified. Conclusion The results of synoptic analysis of pressure patterns related to blocking effective on the occurrence of heavy rainfall in Tabriz area indicate the formation of blocking phenomenon of high pressure type on the region. This system stops the movement of air circulation patterns, during which the patterns governing the atmosphere remain in place for several days. In the face of this system, the waves of the western winds are divided into two branches, north and south. This allows the waves to travel further north or south.
Geomorphology
Batoul Zeinali; Mahdei Aalijahan; fatemeh dashtbani; Rahim Fazeli
Abstract
Floods are one of the most destructive atmospheric hazards which push different communities all over the world to suffer from life and financial damages. The present research has the aim of detection of synoptic and hydrometeorology features of flood in Herochay. For this goal, the data from daily rainfall ...
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Floods are one of the most destructive atmospheric hazards which push different communities all over the world to suffer from life and financial damages. The present research has the aim of detection of synoptic and hydrometeorology features of flood in Herochay. For this goal, the data from daily rainfall of stations in Khalkhal, Khanghah, Arpachayi and Lamber and the data from Hydrometer station in River Kivichay was used to detect the rainfall and flood happened and for synoptic inspection of this phenomenon, the data from Sea level pressure, upper layers of atmosphere like Geopotential high, Omega, Orbital wind, Meridional wind and Relative humidity in levels of 500 to 1000 HPA was used. The obtained results show that presence of low-pressure system on the surface of ground, occurrence of blocking and located of the study area on the east of the trough on the upper levels, negativity of atmospheric eddies and omega on different levels with humid supply of Black Sea and Mediterranean sea on the levels of 500 to 700 HPA, Red sea and Persian Gulf and Oman Sea on the levels of 850 and Caspian Sea on the levels of 925 and 1000 HPA have prepared the conditions needed for generation of instability over the atmosphere of the studied area. The mentioned conditions have caused intense thunderstorm and increase of Herochay discharge and generation of flood in that region.
Mitra Amini; Hasan Lashkary; Mostafa Karampour; Zahra Hojaty
Volume 17, Issue 43 , October 2013, , Pages 1-20
Abstract
The aim of present study is the synoptic analysis of systems having by heavy precipitation on the Kashkan basin. After study of 34-years statistics from stations for basin and its environments three storms by maximum precipitation were selected. The results of study of weather maps, humidity, earth surface ...
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The aim of present study is the synoptic analysis of systems having by heavy precipitation on the Kashkan basin. After study of 34-years statistics from stations for basin and its environments three storms by maximum precipitation were selected. The results of study of weather maps, humidity, earth surface pressure difference and 850 hPa of 48 hours before and after storms, showed that with regard to the fact that three selected storms have out of heavy storms during statistics period occurred in various seasons of the year, their generating system was equal and Sudan-Mediterranean merger system pattern generated maximum precipitation. Synoptic conditions in three chosen storms are: 1-High pressure over Europe northwest and influx of the cold weather in higher latitudes toward low pressure that is situated in east Mediterranean, 2-Sudan low pressure nutrition and motion toward northeast. 3-Days that maximum precipitation has occurred in the basin. These low pressure systems are merged with each other in east of Iraq, and high pressure situated on east of Iran with influx of cold weather over Oman and Arab seas on the one hand and presence of anticyclone in Arabia have caused humidity transfer inside low pressure system situated over west of Iran and generated maximum precipitation.
Afsaneh Abbassi; Hoshang Ghaemi
Volume 17, Issue 43 , October 2013, , Pages 145-168
Abstract
In this research five synoptic stations are selected including Mehrabad, Karaj, Gazvin, Ramsar and Noshahr. After analysis and processing of the parameters such as wind speed, dew point, pressure and storm coefficient data, PMP in continuation of 24 and 48 hours for related basin was estimated, in order ...
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In this research five synoptic stations are selected including Mehrabad, Karaj, Gazvin, Ramsar and Noshahr. After analysis and processing of the parameters such as wind speed, dew point, pressure and storm coefficient data, PMP in continuation of 24 and 48 hours for related basin was estimated, in order of 140/56 , 254/ 58mm. Considering resulted number and obtained flow in 1374/68 and 40% ronoff average daily flow we estimated 550 , which in comparison with the maximum daily flow in Siera (dam entrance) station with 20 years statistical period which is 154/54 for being acceptable. According to synoptic charts, three rainfall systems caused 24 hours Maximum precipitation turn in 48 hours.
Saeed Jahanbakhsh; Fatemeh Jafary shandy; Fereshteh Hosseinalipourgazy
Volume 16, Issue 42 , March 2013, , Pages 113-138
Abstract
In order to identify synoptic super heavy rain patterns (precipitation exceeding 50 millimeters a day) in Azerbaijan region, the daily precipitation data of 23 rain gauges were studied by six-hour precipitation synopsis from 1963 to 2005. The data were analyzed through hierarchical clustering analysis, ...
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In order to identify synoptic super heavy rain patterns (precipitation exceeding 50 millimeters a day) in Azerbaijan region, the daily precipitation data of 23 rain gauges were studied by six-hour precipitation synopsis from 1963 to 2005. The data were analyzed through hierarchical clustering analysis, specifically Ward cluster analysis in GRADS, MATLAB, and SURFFER softwares to identify the relationship between the higher-atmosphere circulation patterns and super heavy rain events in the studied region. Results demonstrated three different active circulation patterns in the region, for each pattern a single representative day was introduced for super heavy rain events's analysis. The spatial alignment of the precipitation pattern points out a relationship between the temporal distributions of super heavy rain events in region with the latitude. Significant relationships are existent between EastBlack Sea-NorthMediteranehSea, and Black Sea trough pattern and super heavy rain events in the studied region. The results play an important role in the prediction of heavy rain events in the region.
