Investigate the nature and structure of the atmospheric circulation during spring pervasive rains Iran

Atmospheric circulation patterns play a major role in the distribution and geographical distribution of precipitation. According to the researchers views Changes climatic circulation patterns are Controller swing shift and also intensity of precipitation and atmospheric moisture content changes (Trenberth et al., 2003: 327-339; Emori and Brown, 2005). So that increases in atmospheric temperature will follow moisture content increases (Trenberth et al., 2003; Meehl et al., 2007). On the other hand, changes in precipitation patterns may be affected by carbon dioxide. That the increase in greenhouse gases how much of the affect climate processes is still in question. But is obvious that the density increases the concentration of greenhouse gases directly or indirectly climate elements, both spatially and in terms of time is affected (colins 2013: 126; Chadwick et al 2013: 610-615). However, many studies have shown that rainfall patterns in tropical areas, especially over the oceans are heavily influenced by changes in temperature (SST) patterns of sea level (Xie et al., 2010; Chadwick et al., 2013: 3803-3822; Ma and Xie, 2013: 2482-2501; Huang et al., 2013: 966-986).
In order to perform Analysis an extensive rains of spring in Iran In this study, is used two groups different environmental data that the data are as follows: 1. Environmental Data: This group of data through interpolation of Daily rainfall spring quantities station in April (April), May (May) and June (June) throughout the country And for a period of1961 to 2010 (4650 days), Using daily precipitation data from 551 Synoptic and climatology stations Had been received from Meteorological Organization Country, were Sort and Interpolation. Finally, by combining these three matrices, Matrix dimensions was obtained studied period (4650×7187). In this study, is said rainy day to day At least one millimeter per day and more experienced. After identifying rainy days percent coverage (pervasive of precipitation) was considered Which for this purpose, given that most researchers in their studies Have chosen Fifty percent coverage for pervasive This day was chosen to cover 50% And finally selected 265 days and was examined and analyzed. Atmospheric data: This data is consists of data sea level pressure and geopotential height at 500 hPa zonal and meridional wind data Which has been received from the database National Center for Environmental Prediction and of the National Center for Atmospheric Research (National Centers for Environmental Prediction / National Center for Atmospheric Research).
The results of this study showed that: The results of the descriptive analysis spring rainfall shows that pervasive and spring rains Towards June While the had a significant reduction is high Spatial Coefficient of variation In between central and southern parts from spatial variation have been more.
The results of the study showed that Four pattern Saudi low pressure- Iran central low pressure, Europe low pressure - Sudan low pressure, Persian Gulf low pressure- Siberian high pressure pattern and multi-core pattern Middle East low pressure The largest role have in pervasive rainfall in spring. In all four pattern Cold air advection high latitudes on Thermal low pressures Low latitudes is causes Extreme Temperature and pressure gradient Resulting in prepare the frontogenesis. Also convergence centers 1000 hPa in these patterns is consistent with low pressure systems. Air high pressure centers to take his side and in contrast to the cold weather tabs high pressure centers due to rising air and create instability in areas under their influence, especially Iran. In 1000 hPa level moisture flux maps humidity injection has been done mainly through the anticyclone on the Arabian Sea into the Sudanese system and strengthen it by injecting humidity from the Red Sea and the Persian Gulf. So that the Cold air advection high pressure centers tabs on the system have been due to its dynamic and moisture transport in the North to the Persian Gulf and Iraq (just in front trough Mediterranean at 500 hPa level). Also, according to the maps Front Genesis at 850 hPa at All patterns are frontogenesis mainly in accordance with the transmission path is hot and humid weather southern extends north.
Spring rains also have daily rise and fall with high spatial variation coefficients In between towards month June this will be more significant changes. The results of the study showed that Four pattern Saudi low pressure- Iran central low pressure, Europe low pressure - Sudan low pressure, Persian Gulf low pressure- Siberian high pressure pattern and multi-core pattern Middle East low pressure The largest role have in pervasive rainfall in spring.