مخاطرات محیط طبیعی (Mar 2017)
Analysis of the position of jet streams and moisture flux associated with extreme rainfall in the western regions of Iran
Abstract
The aim of this study is to identify and analyze the position of the jet streams and moisture flux associated with extreme rainfall in the western regions of Iran during the period (1961-2010), using the synoptic method, that four models were discovered in this area. To recognize the importance of jet streams in the formation of extreme precipitation, Network data levels in heights of 200, 300, 400 and 500 hp for these days, a series of data re-induction of protein NCEP / NCAR, was extracted by using the GrADS software and then proceed to check the total moisture flux convergence and divergence of the balance of 1000 hPa to 400 hPa levels, for each of the four synoptic patterns discussed above. To identify sources of nourishing the moisture such as rain, as well as identify the extent of nourishing the high levels of moisture into this system, rainfall in the region this work was done. Results showed that extreme temperature difference between the surface and high levels in the cold season is due to the presence of polar high-latitudes of the northern and western winds activities (Along with the creation and transfer cold holes and deep through landing). So, in a situation of instability west, the presence of a low-pressure core at high levels and rapid flow of warm and moist air at low levels is effective. The Severe convective low-level rise has been caused by western winds along the polar front. In this way, the polar jet streams accompany landing of western winds with speeds of more than 60 meters per second along. Left Out in the core jet stream (second quarter) that matches the atmosphere of the West, the curvature of the winds into the Arctic air mass will cause the decrease in curved volubility and increase in its area. As a result of the expansion of the air mass at high levels upside and unstable air mass will form.The curvature of the meridian wind jet streams toward the poles cause warm temperatures at the front axle of landing?
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