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IJRSP Vol.41(4) [August 2012] >


Title: Regional climate model simulations of the 2009 Indian summer monsoon
Authors: Bhate, Jyoti
Unnikrishnan, C K
Rajeevan, M
Keywords: Rainfall simulation
Regional climate model
Sea surface temperature
Issue Date: Aug-2012
Publisher: NISCAIR-CSIR, India
PACS No.: 92.60.jf; 92.40.eg
Abstract: Using a regional climate model, the 2009 Indian summer monsoon circulation and rainfall are simulated using observed sea surface temperatures as boundary conditions. For this purpose, the Weather Research and Forecasting (WRF) model (V 3.2) was used as a regional climate model. The model simulations were made for the period 1 May to 30 September with 1 May initial conditions with two domains of 45 km and 15 km and 51 vertical levels. The large scale monsoon circulation and rainfall patterns simulated by the model were examined along with the diurnal and intra-seasonal variations during the 2009 monsoon season using the TRMM 3G68 rainfall data. The results showed a wet bias in the model rainfall simulations over the Indian region with more rainfall in the model compared to the TRMM rainfall observations. This wet bias was attributed to stronger low level monsoon flow in the model simulations over the Indian region. Even though, the model simulations of atmospheric humidity are reasonably accurate, the positive bias in the low level vorticity contributed to the wet bias of rainfall over the Indian region. Model simulations showed errors in characterizing the diurnal variation of monsoon rainfall over the Indian region, especially in the observed phase angle (time of rainfall peak). The model simulations could not capture the observed early morning rainfall peak along the foothills of Himalayas caused by katabatic wind flow over the hills. Model simulations of amplitude of diurnal variation are, however, comparable with the observed amplitude derived from TRMM satellite data. Model simulations also showed encouraging results in simulating the intra-seasonal rainfall variations over the central Indian region and the monsoon onset phase over the Kerala coast.
Page(s): 488-500
CC License:  CC Attribution-Noncommercial-No Derivative Works 2.5 India
ISSN: 0975-105X (Online); 0367-8393 (Print)
Source:IJRSP Vol.41(4) [August 2012]

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