Climatology
Mostafa Karimi; Faramarz Khoshakhlagh; ali akbar shamsi por; fahimeh noruzi
Volume 23, Issue 69 , December 2019, , Pages 233-255
Abstract
Large-scale circulation patterns are controlling climatic conditions and especially precipitation of the area. The purpose of the study is investigating the relationship between circulation patterns of Arabian subtropical anticyclone and Iran precipitation. For this reason, was used re-analysis data ...
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Large-scale circulation patterns are controlling climatic conditions and especially precipitation of the area. The purpose of the study is investigating the relationship between circulation patterns of Arabian subtropical anticyclone and Iran precipitation. For this reason, was used re-analysis data of geo-potential height form European Center for Medium-Range Weather forecasts (ECMWF), with spatial resolution of 1*1 degree and correlation distance cluster analysis. Circulation patterns at 30 to 80 degrees the East longitudes and5 to 30degrees north latitudes and the period of11years (2000- 2010) was calculated. The results showed that the patterns in terms of occurrence were divided the patterns of the cold period, the warm period and the transition period. During the cold period anticyclone is located at down latitudes on the Arabian sea and Gulf of Aden and have precipitation more areas of Iran that maximum amount of precipitation is related to the second pattern. In the patterns of transition period Arabian anticyclone sent a southwest clockwise current in to the trough East Mediterranean is effective in the occurrence of precipitation in the area of North and Northwest of the country. In the patterns warm period the anticyclone caused the anticyclone conditions on country and has been as a barrier to entry precipitation systems.
Climatology
Aliakbar Shamsipoor Shamsipoor; Seyfolah Kaki; Ayob Jafari; Seyd Maysam Jasemi
Volume 22, Issue 64 , September 2018, , Pages 149-167
Abstract
The aim of the research is recognizing mechanisms of the heavy rainfalls in the west and southwest of Iran using synoptic and thermodynamic method. For analysis of case study at April 2016, At first was obtained and calculated hourly rainfall data from 70 weather stations in the research area and 10 ...
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The aim of the research is recognizing mechanisms of the heavy rainfalls in the west and southwest of Iran using synoptic and thermodynamic method. For analysis of case study at April 2016, At first was obtained and calculated hourly rainfall data from 70 weather stations in the research area and 10 weather stations bordering the research area. Then rainfall amounts in stations were calculated and zoned using Arc/Map10. After that Ki, Li, TTi, Cape and SWEAT instability indexes was calculated for Kermanshah and Ahwaz weather stations. Finally, the synoptic maps were analyzed. According to instability indexes, mostly atmospheric instability has been moderate and favorable conditions could be observed for convection and thunder storm, lightening and snow fall. The analysis of the sea level synoptic maps have shown that a few days before the rainfall, the study area has been under the influence of the Siberian high, and simultaneously cyclones centers were formed above the Mediterranean Sea. Their eastern-ward movements created the condition for instability and rainfall in the area. Cold air downfall from high-pressure centers toward the backside of the Mediterranean trough and lower latitudes beside the dislocation of warm humid air to the fore side of the trough created the front and resulted in intensifying the rainy system that finally resulted in heavy rainfall in the area. The atmospheric physical and dynamic indexes show that during the rainfall, voracity positive values, jet stream wind and negative omega figures were in their maximum.
