辐射和积云对流过程对大气辐射通量的影响

The impacts of the radiation and cumulus convective parameterization on the radiation fluxes in SAMIL

中文关键词:  大气环流模式， 辐射方案， 积云对流方案，辐射通量

英文关键词:SAMIL, Radiation scheme, Cumulus convective scheme, Radiation flux

中文摘要:

      基于中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室发展的全球大气环流谱模式（SAMIL-R42L26），研究了澳大利亚气象局研究中心（BMRC）新辐射方案和新Zhang McFarlane积云对流方案对大气辐射通量模拟的影响。新辐射方案相比原辐射方案在辐射计算光谱分辨率、气体吸收和计算效率等方面作了很多改进，其对大气辐射通量的模拟能力相应提高。在晴空条件下，大气顶出射长波、大气吸收短波和地表入射短波等与观测的偏差较原辐射方案明显减小，尤其是在对流活跃区域。在云天条件下大气辐射通量与观测的偏差也较原辐射方案减小，但其偏差依然较大，这与模式中积云对流参数化方案模拟能力不足引起的辐射通量偏差有关。为此，换用了新Zhang McFarlane积云对流方案，其结果表明，对流活跃区水汽含量显著增加，原对流方案中偏强的“双赤道辐合带”现象明显减弱，赤道辐合带地区的大气辐射通量偏差有明显减小，在海洋地区晴空大气顶出射长波和地表入射短波的量值及空间分布均接近观测结果，同时大气顶全球平均能量收支的年变化和观测结果趋于一致，其中模拟的全球年平均大气顶能量收支和观测的偏差不到 0.6 W/m 2。试验结果同时表明，在未来研究中引入气溶胶分布、调整相关的云物理和陆面过程等物理参数化方案是进一步提高SAMIL R42L26辐射通量模拟性能的关键。

英文摘要:

      A new radiation scheme is included into the general circulation model (SAMIL-R42L26) of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP). Compared with the previous radiation scheme (SES1), spectral interval, gas absorption, computation efficiency etc. have been improved in the new radiation scheme (SES2), so the radiative flux simulated by SES2 is improved correspondingly. In clear sky conditions, the biases of long wave flux at the top of the atmosphere (TOA), short wave flux absorbed by atmosphere, and the incident short wave flux at surface are reduced a lot especially in convection active regions. In cloud-sky conditions, the biases of radiative flux are also reduced to some extent. However, there still exist large biases, which are closely related to the poor performance of the cumulus convective parameterization. Hence, we include a new cumulus convective parameterization into the SAMIL R42L26 to further improve the simulation results. It is shown that water vapor content is greatly increased along the equator and the strong “double ITCZ” is eliminated with the new convective scheme. At the same time, the biases of radiative flux are reduced significantly along the equatorial convergence zone. The clear-sky long wave flux at TOA, the incident short wave flux over the oceans, and the global mean energy budget at TOA are closer to the observations. Our study also shows that there are still some biases in the radiative flux simulation, which might be related to the aerosol effect, the land surface process, and the cloud physics. These are to be investigated in the future.