Simulations of Tropical Circulation and Winter Precipitation Over North India: an Application of a Tropical Band Version of Regional Climate Model (RegT-Band)

Abstract

In the present study, simulations have been carried out to study the relationship between winter-time precipitations and the large-scale global forcing (ENSO) using the tropical band version of Regional Climate Model (RegT-Band) for 5 El Nin˜o and 4 La Nin˜a years. The RegT-Band model is integrated with the observed sea-surface temperature and lateral boundary conditions from National Center for Environmental Prediction (NCEP)- Department of Energy (DOE) reanalysis 2 (NCEP-DOE2). The model domain extends from 50S to 50N and covers the entire tropics at a grid spacing of 45 km, i.e., it includes lateral boundary forcing only at the southern and northern boundaries. The performance evaluation of the model in capturing the large-scale fields followed by ENSO response with winter-time precipitation has been carried out by using model simulations against NCEP-DOE2 and Global Precipitation Climatology Project (GPCP) precipitation data. The analysis suggests that the model is able to reproduce the upper airfields and large-scale precipitation during winter time, although the model has some systematic biases compared to the observations. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. It is noticed that the RegT-Band model simulations are able to bring out the observed features reasonably well. Therefore, this preliminary study indicates that the tropical band version of the regional climate model can be effectively used for the better understanding of the large-scale global forcing.