GRAPES_Meso模式中两种双参数云微物理方案对冷云过程模拟的比较研究

基于GEAPES_Meso模式,分别利用Morrison方案和WDM6方案对2017年1月5—7日一次以层状云为占主导的云系中冷云过程进行模拟和对比分析,评估两种云微物理方案对本次冷云过程云微物理及云辐射过程演变的影响。结果表明:包含丰富暖云和冷云物理过程的Morrison双参数云微物理方案模拟效果优于WDM6方案。Morrison方案模拟的云水路径、云冰有效半径及云光学厚度均大于WDM6方案的模拟结果,而模拟云水有效半径小于WDM6的模拟结果。Morrison方案较WDM6方案对云水(云冰)有效半径、云光学厚度、云水路径及地表短波辐射的水平分布模拟结果更为准确。由于Morrison方案模拟云水有效半径大于WDM6方案,云冰有效半径小于WDM6方案,导致Morrison方案模拟的云水和雪混合比大于WDM6方案模拟结果,而雨水、云冰和霰的混合比则明显小于WDM6方案。相较于WDM6方案,Morrison方案模拟的地表短波辐射水平分布和量值一致性更接近于CERES卫星结果。两种方案中包含的不同微物理过程将影响潜热和感热过程,其中,Morrison方案模拟海平面温度和辐射通量小于WDM6方案,该差异在陆地区域更显著。

大气模式比较计划(AMIP)

文章介绍了ＡＭＩＰ及参加ＡＭＩＰ的模式的模拟概况，指出几乎所有模式都能够模拟出大尺度大气环流的平均季节结构，但没有任何一个模式在各方面都好，而且模式一般高估了季节循环的方差，低估了年际变率，并且各个模式在模拟不同气候要素的时空变化时彼此差别也较大．文章还重点讨论了云辐射及陆面水文过程，指出观测与模拟的高低云量存在较大差异，而云量可能并不是影响辐射平衡的唯一因子，云的季节变化与气温的年循环存在着正相关．大多数模式对非对流性降水模拟得不好．对ＩＴＣＺ、ＳＰＣＺ及亚洲季风区的位置模拟较好，但雨量与观测值差别较大．另外，没有一个模式能模拟出梅雨雨带．ＡＭＩＰ的各个模式对土壤湿度的处理方法各有不同，但模拟结果彼此差别较大，与仅有的观测值差别也很大．最后对几个主要模式的改进工作及其效果做了总结，并对１９９６年开始的ＡＭＩＰ２的工作方向做了简单介绍．

Precipitation responses to radiative processes of water- and ice-clouds: an equilibrium cloud-resolving modeling study

Cloud radiative processes are important in regulating weather and climate. Precipitation responses to radiative processes of water- and ice-clouds are investigated by analyzing mean equilibrium simulation data from a series of two-dimensional cloud-resolving model sensitivity experiments in this study. The model is imposed by zero vertical velocity.The exclusion of water radiative processes in the presence of ice radiative processes, as well as the removal of ice radiative processes, enhances tropospheric Iongwave radiative cooling and lowers air temperature and the saturation mixing ratio. The reduction in the saturation mixing ratio leads to an increase in vapor condensation and an associated release of latent heat, which increases rainfall. The elimination of water radiative processes strengthens local atmospheric warming Iongwave radiative cooling. The enhanced warming melting of graupel, which increases rainfa n the upper troposphere via a reduction in ncreases the rain source via an increase in the

Reducing the biases in shortwave cloud radiative forcing in tropical and subtropical regions from the perspective of boundary layer processes

Biases in shortwave cloud radiative forcing(SWCF), which cause overestimates in tropical regions and underestimates in subtropical marine stratocumulus regions, are common in many climate models. Here, two boundary layer processes are investigated in the atmospheric model GAMIL2, entrainment at the top of the boundary layer and longwave radiative cooling at the top of stratocumulus clouds, in order to reduce biases and reveal the mechanisms underlying these processes. Our results show that including the entrainment process in the model can reduce negative SWCF biases in most tropical regions but increases positive SWCF biases in subtropical marine stratocumulus regions. This occurs because entrainment reduces the low-level cloud fraction and its cloud liquid water content by suppressing the vertical turbulent diffusion in the boundary layer and decreasing the relative humidity when warm and dry free atmosphere is entrained in the boundary layer. Longwave radiative cooling at the top of stratocumulus clouds can enhance turbulent diffusion within the stratocumulus-topped boundary layer. When combined with the entrainment process, longwave radiative cooling reduces the positive SWCF biases in subtropical marine stratocumulus regions that are observed using the entrainment process alone. The incorporation of these two boundary layer processes improves the simulated SWCF in tropical and subtropical regions in GAMIL2.