Monsoon Regimes and Processes in CCSM4. Part I: The Asian-Australian Monsoon

Meehl, Gerald A and Arblaster, Julie M and Caron, Julie M and Annamalai, H and Jochum, Markus and Chakraborty, Arindam and Murtugudde, Raghu (2012) Monsoon Regimes and Processes in CCSM4. Part I: The Asian-Australian Monsoon. In: Journal of Climate, 25 (8). pp. 2583-2608.

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Abstract

The simulation characteristics of the Asian-Australian monsoon are documented for the Community Climate System Model, version 4 (CCSM4). This is the first part of a two part series examining monsoon regimes in the global tropics in the CCSM4. Comparisons are made to an Atmospheric Model Intercomparison Project (AMIP) simulation of the atmospheric component in CCSM4 Community Atmosphere Model, version 4, (CAM4)] to deduce differences in the monsoon simulations run with observed sea surface temperatures (SSTs) and with ocean-atmosphere coupling. These simulations are also compared to a previous version of the model (CCSM3) to evaluate progress. In general, monsoon rainfall is too heavy in the uncoupled AMIP run with CAM4, and monsoon rainfall amounts are generally better simulated with ocean coupling in CCSM4. Most aspects of the Asian-Australian monsoon simulations are improved in CCSM4 compared to CCSM3. There is a reduction of the systematic error of rainfall over the tropical Indian Ocean for the South Asian monsoon, and well-simulated connections between SSTs in the Bay of Bengal and regional South Asian monsoon precipitation. The pattern of rainfall in the Australian monsoon is closer to observations in part because of contributions from the improvements of the Indonesian Throughflow and diapycnal diffusion in CCSM4. Intraseasonal variability of the Asian-Australian monsoon is much improved in CCSM4 compared to CCSM3 both in terms of eastward and northward propagation characteristics, though it is still somewhat weaker than observed. An improved simulation of El Nino in CCSM4 contributes to more realistic connections between the Asian-Australian monsoon and El Nino-Southern Oscillation (ENSO), though there is considerable decadal and century time scale variability of the strength of the monsoon-ENSO connection.

Item Type:	Journal Article
Publication:	Journal of Climate
Publisher:	American Meteorological Society
Additional Information:	Copyright of this article is belongs to American Meteorological Society.
Keywords:	Asia;Australia;Indian Ocean;Maritime Continent;Pacific Ocean;Biennial oscillation;Deep convection;ENSO;Madden-Julian oscillation;Orographic effects;Southern Oscillation, Topographic effects;Walker circulation;Monsoons;Climate models;Model comparison;Annual variations;Biennial oscillation;Interannual variability;Interdecadal variability;Intraseasonal variability;Seasonal cycle;Southern Oscillation;Tropical variabilty
Department/Centre:	Division of Mechanical Sciences > Divecha Centre for Climate Change Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	14 Aug 2012 07:00
Last Modified:	14 Aug 2012 07:21
URI:	http://eprints.iisc.ac.in/id/eprint/44498

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