Sensitivity Analysis of Different Convection Schemes and Domain Centers for Numerical Simulation of Winter Precipitation Over Iran

This paper qualifies the impact of different convection schemes and domain centers on the simulation of two dry and wet winter precipitations of 1997 and 2000 over Iran using RegCM3 numerical climate model. The model uses a compressible, finite difference with hydrostatic equilibrium in sigma coordinate and a semi-implicit algorithm for reduction of horizontal diffzLsion. In this st ndy, sensitwity of the RegCM3 regional climate model has been analyzed using different convection schemes, including Greli-A S, Grell- FC, Emanuel and K uo schemes and different domain center locations including Himalaya, Mediterranean sea, han and Indian ocean (near Pakistan southern border). NNRPJ data with a 5-degree resoluiion.os well as GLCC and GTOPO dataset are used as initial and boundary conditions. land use and topography data, respectively. We found that the perjorttuince of the Model strongly depends on the location of the domain center, for example when the center of the domain is located over Himalaya then the results for the precipitation are reasonobls; better especially when a Siberian high pressure develops over Iran. With K1W scheme.the minimum of bias and MAE are -0.7mm and 0.6mm for dry year of 2000, but with Grell scheme the error is found to be a minimum compared to other configurations of the model both in dry and wet seasons. In all experiments the precipitation amounts arc underestimated when compared to corresponding observations. The largest difference occurred in Himolau« experiment. Moreovcr, we found that there is an eastward shift in Caspian Sea precipitation patt.ern. in all experiments. It is also found that CRU reanalysis data cannot be considered as a reference for calibration of RegCM3 over Iran.