The Impacts of the Modified Tiedtke Cumulus Convective Parameterization Scheme on the Tropical Rainfall Simulation in SAMIL Model

In general there exists“double ITCZ” bias either in coupled models or in atmospheric general circulation models; so does in the new version of the LASG/IAP (State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics, Chinese Academy of Sciences) spectral atmospheric model SAMIL_R42L26: there is less rainfall near the equator while more rainfall on both the north and south sides. This bias can affect the tropical circulations and global energy balance. However, the bias can be weakened through the modified Tiedtke cumulus convective parameterization scheme. The new scheme can affect the distribution of temperature in the lower troposphere, even on the surface, and the associated wind and divergence fields are also changed, which in turn create conditions for the further development of convection, forming a positive feedback. Finally the eastward extension of precipitation bias along the SPCZ (Southern Pacific Convergence Zone) can be effectively restrained, and at the same time, the insufficient rainfall over the tropical warm pool is increased.