NAME =  A. Routray  
ORGANIZATION =  Indian Institute of Technology, Delhi  
ADDRESS =  Centre for Atmospheric Sciences, IIT Delhi, Hauz Khas, New Delhi-16  
COUNTRY =  India  
PHONE =  91-11-26596052  
FAX =  91-11-26591386, 26862037  
E-MAIL =  ashishroutray@yahoo.com  
POSTER_ONLY =  no  
THEME =  T2  
DATE =  31-Jul-04-15:47:09  
ABSID = T2AR31Jul04154709 
TITLE = Study of heavy rainfall event over west-coast of India using Analysis Nudging in MM5 during ARMEX-I 
AUTHOR_1 = A. Routray 
INSTITUTION_1 = Indian Institute of Technology, Delhi 
PRESENTER = AUTHOR_1 
ABSTRACT =   Abstract
	Several heavy rainfall episodes are observed over the west coast of India during Arabian Sea Monsoon Experiment-I (ARMEX-I). In the present study an attempt is made to numerically simulate one such heavy rainfall event observed during 25-28 June 2002 using mesoscale modeling system (MM5). 	The skill and efficiency of a numerical model mostly varies with the quality of initial values, accuracy in the parameterization of physical processes and the applied horizontal and vertical resolution. 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 when large scale global analyses are used as initial and boundary condition. Therefore 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.
	The model simulated fields’ viz. sea level pressure, wind and precipitation are compared with the corresponding verification analysis /observations. Results indicate that the simulations are improved when four dimensional data assimilation using analysis nudging is performed. The improvement in the rainfall forecasts are due to improved initial conditions produced by the analysis nudging.

Key words: ARMEX; Analysis nudging; heavy rainfall; MM5.