Study of heavy rainfall event over west coast of India using analysis nudging in MM5 during ARMEX-I

Abstract

An attempt is made to numerically simulate one heavy rainfall event observed during 7-9 August 2002 along the west coast of India using mesoscale modeling system (MM5). The prime objective of the present study is to investigate the impact of analysis nudging using conventional and non-conventional observations at high-resolution in the mesoscale model. Two numerical experiments are carried out with MM5 having a double nested domain viz. 60 km (coarse) and 20 km (inner) to study this heavy rainfall event. The first experiment, namely the control simulation (CNTL), global analyses is used as initial and boundary conditions. It is noticed that the model is not able to comprehensively capture the prominent features associated with organized convective processes. A second experiment, called the nudging simulation (NUDG), is carried out where the model initial and boundary conditions are improved after the insertion of observational data. Thereafter, 12 hrs analysis nudging is also applied to further improve the initial condition, before the model is allowed for free integration. Results indicate that the simulations are improved when four dimensional data assimilation using analysis nudging is performed.