| Abstrakt: |
The geographical location of southwest Asian countries relative to the general circulation system of the atmosphere and proximity to large-scale systems such as the Arabian Anticyclone (AA) have caused the precipitation period to be limited to a certain part of the year. Given the distance from and proximity to this system, the period of precipitation in the southern half of Iran varies between 6 and 8 months. Under normal conditions, precipitation in southern Iran and the southern coast of the Persian Gulf begins in early October and continues until the end of May. To the more southern latitudes, this period begins with a delay of one month and ends one month earlier. The purpose of this study is to examine the role of spatial displacement and the dynamic structure of Arabian anticyclone in shortening the precipitation period in southern Iran. For this purpose, 36-year precipitation statistics of 30 main stations in southern Iran were received from the National Meteorological Center of Iran. The beginning and end of precipitation were determined for all years. Based on the selected criteria, precipitation periods of less than 160 days were selected as short precipitation periods. Factor analysis index was used to extract synoptic patterns, it was also used to extract the core location of Arabian anti-cyclone centers and rotate it from sea level atmospheric data up to 500 hPa from the National Oceanic and Atmospheric Administration (NCEP/NCAR) dataset for years with short precipitation periods. The results revealed that in years when the precipitation period is shorter than usual, Arabian anticyclone has started to move eastward and southward later. As a result, located on the northwest side of the Arabian anticyclone and southwestern Iran, it prevents the expansion of precipitation systems, especially the Sudanese system in the region. At the same time, at the end of the rainy season, there is an early shift to westward and northward; in these years, sometimes the rains do not start until early December, and at the end, with early movement and turning anticyclone to summer conditions, the rains stop from late March or early May. Examination of the prevailing synoptic pattern at the beginning and end of the rainy season showed that due to the obstruction of the Arabian anticyclone between the Red Sea and Iran during these years, the Sudan low-pressure troughs spread northwards and entered the eastern Mediterranean. [ABSTRACT FROM AUTHOR] |
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