Investigating the Effect of Zagros Mountains Range on Sudanese Rainfall Changes in Western Iran

Zagros Mountains range as the most important face of topography in western Iran can affect the activity of precipitation systems in addition to the effect of orography on the occurrence of precipitation. The objective of this paper is to analyze the enhancing effect of the Zagros Mountains on the Sudanese system. For this purpose, three one-day rainfall samples including December 2, 1999, March 30, 2012, and March 20, 2015 were selected and analyzed using factor analysis among one-day Sudanese rainfall systems during the period  from 1996 to 2017. The method used was synoptic analysis of atmospheric parameters and rainfall interpolation model in GIS environment. This study demonstrated that the warm air stream and contact of the Sudanese system with the western and southwestern slopes of Zagros reduced the geo-potential height and formatted a positive vorticity field. Positive vorticity blow to the southeast and inland slopes of Zagros caused upward movements on these slopes. At higher levels of atmosphere, cold air blow in adjacent to warm air blow area of lower levels of atmosphere reduced the geo-potential height of the atmosphere and enhanced the upward movement of the atmosphere. Thus, suitable thermodynamic conditions were provided for the growth and reinforcement of convective clouds and heavy rainfall over the topography surface. In this study, it was found that in all the studied rainfall samples, entrance direction of the system and humidity to region has followed from width and length of wave in middle layer of atmosphere. The results showed that the maximum precipitation was observed in the slopes located in direction of Sudanese rainfall system entrance. Also, precipitation changes on steep slopes of Zagros were also greater than other levels.