Finding the origin and synoptic analysis of atmospheric rivers leading to precipitation in the western and northwestern regions of Iran

In global meteorological literature, atmospheric rivers are defined as long and narrow pathways of intense water vapor transport towards the polar regions in the middle latitudes, typically associated with low-level jet streams along the leading edge of extratropical cyclones. In this study, to identify the origins of the incoming atmospheric rivers to the study area, precipitation systems that occurred at more than half of the region's stations were selected. Then, using vertically integrated water vapor flux data from the east and north of the study area with a spatial resolution of 0.5 x 0.5 degrees, the magnitude of the water vapor flux was calculated. To calculate the magnitude of the flux, data including specific humidity and meridional and zonal winds at pressure levels from 1000 to 300 hPa were used. showed that these rivers have entered northwest and west of Iran from four moisture sources. The sources are the warm southern seas (the Sudan - Red Sea low-pressure pattern), the convergence zone region, the combined source of the Sudan low-pressure system and the Mediterranean circulation, and the Mediterranean Sea. Among these sources, the warm seas of Arabia and Oman and the Red Sea had the largest share in the incoming rivers to the region. These atmospheric rivers have been the strongest in terms of both temporal continuity and moisture flux. They first enter southwest Iran and then into the study area. The atmospheric rivers with the convergence zone source rank second in terms of their contribution to the region's precipitation.