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大气科学  2007 

The Impacts of the Cumulus Convective Parameterization on the Atmospheric Water-Content and Rainfall Simulation in SAMIL

Keywords: general circulation model,cumulus convective parameterization,mass flux convection scheme,shallow convection

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The new version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics(LASG/IAP) spectral atmospheric model SAMIL_R42L26 has been developed and evaluated since 2005.The model shows its ability in representing the global climate,but it also suffers from some problems in simulating precipitation in the tropics,such as the double ITCZ in the central-western Pacific,less precipitation in the equator area and in the mid-latitudes of the Northern Hemisphere,and more in Latin America.These biases seem to result mainly from the treatment of subgrid scale convection,which is parameterized with the Tiedtke's mass flux scheme.A sensitivity experiment shows that these systematic errors are linked each other,and owe their existence mainly to the dry bias of the lower troposphere.In view of these results,several modifications are made to the Tiedtke's mass flux scheme used in SAMIL,and the results show apparent improvements in simulating the climate compared with the control experiment.In particular,the "double ITCZ" is eliminated and the modeled precipitation in the northern tropical area is more realistic.The modified scheme can also reduce both cold and dry biases in the middle troposphere.Results from the compared experiment show that the improvements in the model performance mainly result from the improved shallow convection due to the introduction of the modified convective parameterization.


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