Challenges of Improving the Stratiform Processes in a Coupled Climate Model with Indian Monsoon Perspective
Stratiform rain and associated cloud processes play an important role in the Indian summer monsoon rainfall propagation and distribution. In spite of improvement in model resolution, the parameterization of stratiform cloud processes remains elusive. An attempt is made here to improve the parameterization of stratiform processes of NCEP (National Center for Environmental Prediction) CFSv2 (climate forecast system version 2.0) coupled model for better simulation of the Indian summer monsoon. Physically more realistic cloud microphysics scheme (WSM6) suitably modified with Indian aircraft observation along with a revised simplified Arakawa Schubert (RSAS) and modified radiation parameterization has been implemented in CFSv2. The simulation of stratiform rainfall and its northward propagation by a modified version of CFSv2 (CFSCR) is compared with the default CFSv2. The improved cloud parameterization enables the model to realistically simulate the stratiform rain and its fraction against the convective rain of the model. The CFSCR is also able to improve the stratiform rain efficiency in the model. This development demonstrates that improved cloud processes can resolve the issue of erroneous convective and stratiform fraction in CFSv2.
KeywordsStratiform processes Coupled model Indian monsoon
The authors are grateful to Director, IITM for the encouragement of the study. The authors are grateful to Ministry of Earth Science, Government of India, for funding and IITM HPC is gratefully acknowledged for allowing the CFSv2 run to be accomplished.
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