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.
Climatology
Majied Rezaee Banafshe; Fateme Jaafari Shendi; Fereshte Hosseinalipour Ghazi; Majied Alimohammadi
Abstract
In this study, frequency and location of Moisture Flux Convergence (MFC) related to heavy rainfall have been analyzed using environmental to circulation approach. Based on the threshold of upper 99 percent, we selected 106 days of the super and overall heavy rainfall from IRIMO data base. MFC’s ...
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In this study, frequency and location of Moisture Flux Convergence (MFC) related to heavy rainfall have been analyzed using environmental to circulation approach. Based on the threshold of upper 99 percent, we selected 106 days of the super and overall heavy rainfall from IRIMO data base. MFC’s frequency and their locations have been detected from 00 to 1200 E and 00 to 800 N in the five levels (1000, 925, 850, 700, 600 and 500 HPa level) at 00:00, 06:00, 12:00 and 18:00 UTC. Analysis of MFC indicated that among upper levels, frequency of MFC in 850 hPa, due to high frequency is very important
Majid Rezaee Banafshe; Hoseyn Hossein Alipour Ghazi; Fatemeh Jaffari Shendi; Majid Alimohammadi
Volume 19, Issue 53 , September 2015, , Pages 117-135
Abstract
In this study, the heavy rainfall of Northwest of Iranhas been analyzed using environmental circulation approach. Isohyte maps were depicted using Kriging method on 14*14 km pixels from 21/3/1961 up to 31/12/2004 (a17508× 533 matrix). Based on these interpolated data we selected super heavy rainfalls ...
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In this study, the heavy rainfall of Northwest of Iranhas been analyzed using environmental circulation approach. Isohyte maps were depicted using Kriging method on 14*14 km pixels from 21/3/1961 up to 31/12/2004 (a17508× 533 matrix). Based on these interpolated data we selected super heavy rainfalls for all in Northwest of Iran as a whole. Heavy rainfall and their locations have been detected from 00 to 1200 E and 00 to 800 N in the five this levels (1000, 925, 850, 700, 600 and 500 hPa level) at 00:00, 06:00, 12:00 and 18:00 UTC. The results of this study showed that four thickness circulation patterns play role in producing these super heavy rainfalls. In analysis of these precipitations one representative day was introduced for every circulation pattern. The analysis showed that the circulation patterns 2 justify the most of precipitations. These findings can play an important role in forecasting the precipitation and preventing from flooding in the region.
Seayed Abolfazl Masoudian; Fatemeh Jafari Shendi
Volume 18, Issue 50 , February 2015, , Pages 305-331
Abstract
In this study, heavy rainfall of northern low rainfall region has been analyzed using environmental to circulation approach. In order to analyze these types of rains, Asfezari rain data base is used. A base with daily ranfall includes 15992 days, from 1340.1.1 to 1383. 1437 daily precipitation maps of ...
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In this study, heavy rainfall of northern low rainfall region has been analyzed using environmental to circulation approach. In order to analyze these types of rains, Asfezari rain data base is used. A base with daily ranfall includes 15992 days, from 1340.1.1 to 1383. 1437 daily precipitation maps of northern low rainfall region were created using Kriging method. Mean daily precipitation data for this station has been used. Spatial resolution of these maps were 18 Km*18 Km. So 1406 pixels cover the northern low rainfall region and temporal and spatial behavior of precipitation could be represented by a 1406*362 matrix. We selected 100 days of the heavy rainfall from IRIMO data base. A cluster analysis was applied on this matrix and four different circulation patterns were actived. As a result, 100 occurrences of broad and heavy rainfall have been assimilated according to the sea level pressure, humidiy flux convergensy, stream function and front function exorbitance. Spatial configuration of these patterns showed that the main reason of these rainfalls had been the siberian and Black Sea unticyclones, troughs of Red Sea and Persian Gulf.
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.
