Impact of Vertical profiles on Monsoon rainfall: A case study

Indian Summer Monsoon (ISM) is one of the spectacular features of the global atmospheric general circulation. In recent years, attempts have been made to simulate the climate features by regional climate models. Although the accuracy of the regional atmospheric models has improved dramatically during the past decades, many sources of error still remain. The sources of errors in the numerical weather prediction (NWP) models can be classified into two categories. One is from the model used; reflecting the imperfection of model in resolving the forcing present in the atmosphere and the other source is from observing the initial true state of the atmosphere. The present study examines the impact of assimilation of temperature and water vapour profiles from Atmospheric Infrared Sounder (AIRS) data and Radiosonde observations on WRF for simulation of monsoon active period during 2010. The model used herein is the Weather Research and Forecasting model.The NCEP/NCAR Reanalysis data is used to determine the initial and boundary conditions required for the model integration. For the model validation, ERA,TRMM-3B42,IMD gridded rainfall and Atmospheric Infrared Sounder (AIRS) satellite data used for this study. Upper air observations are also used for assimilating into model. Model has been integrated for 15 days, starting from 25 June, 2010 to 10 July 2010. Analysis revealed that the assimilated profiles of temperature and water vapour are improved the model simulation relatively well. The Root Mean Square Error between IMD and -CTRL is 5.96 mm/day. With Assimilation, the Root Mean Square Error between IMD and Model is reduced and its value is 3.62 mm/day. Rainfall patterns are well improved over central Indian region as well northern part of country reasonably good when compared to model CTRL experiment against to observations (IMD, TRMM). Figure 2, showing that the Rainfall time series over central Indian region. It is showing that the rainfall has good improved with the assimilation when compared to CTRL run against to IMD as well as TRMM observations. The vertical structure of the Temperature (K), water vapour mixing ratio(g/Kg), and vorticity(1e-4) components are improved with assimilation compared to CTRL experiment. In Future study, the same will be checked with Advance assimilation Techniques such as Variational and Ensemble Methods.