干旱区生态环境知识资源中心

Different patterns of pressure systems together with local factors, leads in generation, rising and spread of dust in West of Iran. In this study, to investigate the factors causing the occurrence of dust in Kermanshah province, 132 cases of dust phenomena (code: 06) were selected and analyzed using Kermanshah synoptic station data for the spring and summer seasons in a period of 5 years (2005-2009). The Factor analysis had been implemented and days with higher correlation coefficient extracted, then clustering operation was performed on the data. 4 dust emission patterns were identified and from each pattern, a certain pattern was selected as a representative day. Using GRADS and NCEP data, maps of geopotential heights, wind speed and vorticity advection were produced and analyzed. To identify the source of dust generation, tracing and simulating the path of dust, HYSPLIT model Lagrangian approach of backward trajectory was used. Generally existence of low pressure cells in the central and southern regions of Iran can lead to the convergence and air intake at near ground levels and strong positive vorticity, which result in cyclonic movements in western regions of Iran Including Kermanshah. These results in the transfer of dust from the dry desert areas of Iraq and high speed winds in the lower levels of dust particles in the region has accelerated the transfer rate. Based on the HYSPLIT outputs, major sources of dust generation, were arid zones of Southern Turkey, Iraq deserts, Syria, North East of Saudi Arabia and Kuwait.