Numerical Simulations of the Impacts of Tropical Convective Heating on the Intensity of the Northern Winter Stratospheric Polar Vortex

By applying two different convective parameterization schemes, the AGCM SAMIL/LASG was used to investigate the impacts of tropical convective heating on simulated extratropical stratospheric circulation. The results show that different choices of convective parameterization schemes can markedly influence the simulation of boreal winter stratospheric polar vortex intensity. Comparison of the results from SAMIL with the Manabe convective parameterization scheme showed that the simulation of the northern winter stratospheric polar vortex from SAMIL with Tiedtke scheme was effectively improved, particularly the known “cold bias” in the polar region. Because the maximum convective heating rate in the tropics lies in the upper troposphere in the Tiedtke scheme but in the lower troposphere in the Manabe scheme, the simulated temperature from SAMIL-Tiedtke was found to be warmer (cooler) in the tropical upper (lower) troposphere than that from SAMIL-Manabe. Considering the differences between SAMIL-Tiedtke and SAMIL-Manabe, there are marked warmer temperature anomalies in the tropical upper troposphere, which are coupled with marked cooler anomalies in the tropical lower stratosphere. In autumn, cooler temperature anomalies prevail in the midlatitude upper troposphere, which in turn are coupled with warmer temperature anomalies in the midlatitude stratosphere. In addition, the amplitude of planetary wavenumber-1 during autumn-winter in SAMIL-Tiedtke is also stronger than in SAMIL-Manabe. The stronger planetary wavenumber-1 and the warmer midlatitude stratosphere induce a stronger poleward eddy heat flux into the polar region and result in a weaker and warmer stratospheric polar vortex.