A Study of the Effects of Zagros Mountain Ranges on Mesoscale Westerly Currents Using RegCM

As shown in previous studies, mountain ranges not only have profound impacts on regional climate, such as lee lows and orographic precipitation, but also can affect large scale circulations and global climate, substantially (e.g. Colle, 2004; and Kljun, et al., 2001). Therefore, it is expected that the two large mountain ranges in Iran, Zagros and Alborz, have significant effects on the climate of Iran. To gain detail understanding of the regional climate, we need to study qualitatively and quantitatively the effects of the all dynamical and physical factors, as well as their interactions, on the climate. In this paper we have attempted to investigate the sensitivity of the dynamical structure of .the mesoscale flow and regional physical parameters, temperature and precipitation fields, to the Zagros topography and its land cover. The version 3 of the Regional Climate Model (RegCM3) has been used in the control experiment, and with various modifications in the sensitivity tests. The regional climate models are able to simulate the regional scale flow with great details, especially in the region where forcing is due to complex topographical effect, land-sea contrast, or both (Giorgi, 1990). To investigate the role of mountain chains on the climate of this region, different simulations using RegCM3 are performed and results are analyzed. The main objectives of these simulations are: 1- To examine the ability of RegCM3 in simulating the role of Zagros mountain ranges in the regional climate. 2- To study the effects of Zagros mountain ranges on the dynamics of mesoscale currents over Iran, as well as regional physical parameters.