Tracing dust sources in different atmosphere levels of Tehran using hybrid single-particle lagrangian integrated trajectory (HYSPLIT) model

Abstract

Thepresent study aims to tracing dust sources of Tehran (capital city of Iran)using HYSPLIT model and atmospheric circulationsystems atdifferent levels. The statistical analyses within the period 1981-2005 indicatethat one of the most significant dust events in Tehran province occurred in May2000 and continued for more than 4 days in Abali, Chitgar, Firuzkuh, Karaj andNorth Tehran stations. For this purpose, in order to identify the sources of dustparticles and their directions, firstly, high-level atmospheric data includingzonal and meridional wind, geopotential height at pressure levelof 700 and 850 hPa and atmospheric circulation patterns werestudied from two days before the storm, the first of May until the end of thesecond, fourth and fifth day. By using atmospheric circulation maps, the synoptic systems effective in causing dust events, flowsdirections and their speeds were determined. In this modeling approach, a backwardparticle tracking method was applied to determine the direction of dustparticles, 48 hours before dust storm in Tehran, at three elevations of 100,500 and 1000 meter. With regard to the fact that the pressure systems ofnorthern latitudes are active over Iran in transition period of spring, itshould be noted that the results of the present study were affected by thesesystems. Results indicate that the high-pressure system hovering above theSaudi Arabia and the low-pressure tongue at higher latitudes play an importantrole in forming particle motion patterns and flow speeds of mentioned levels.Using HYSPLIT Lagrangian model shows the effects of arid regions of SaudiArabia, Iraq and some parts of Syria on producing greatest amount of dustparticles transferred to Tehran.