单层不同类型云系统的特性及高云重叠的影响

Characteristics of Various Types of Cloud Systems in Single Layers and the Associated Impacts of the Overlapping High Clouds

通过时空匹配主动遥感产品(2B-CLDCLASS-LIDAR)的云类型参数与被动遥感产品(Clouds and the Earth's Radiant Energy System-Single Scanner Footprint:CERES-SSF)的云宏微观物理特性和大气层顶处辐射通量参数(2007/01~2010/12),本文在全球尺度上统计分析了不同类型单层云以及高云重叠的双层云的云特性和大气层顶云辐射强迫。尽管主动和被动卫星遥感产品相互独立,但被动遥感反演的云光学厚度和云相态等参数能够合理反映不同类型云之间的差异。不同类型单层云表现出的云特性差异能进一步影响大气层顶的辐射能量收支。本文通过对比不同类型单层云的Clouds and the Earth's Radiant Energy System(CERES)视场样本数量随短波和长波云辐射强迫的分布,发现它们的高值区形状、位置和面积存在差异,反映了其各自独特的辐射特性。层积云的CERES视场样本数量密集区类似椭球结构,而其它云类型则趋于指数曲线结构。当进一步考虑高云重叠的影响时,统计结果表明:重叠的高云比高云单层状态有更蔽光和更厚的云体;高云重叠的底层云类型则比其单层状态有更透光和更薄的云体;高云重叠的双层云(除了高云重叠积云)对地气系统的净冷却效应要弱于其低层云类型单层状态。本文研究结果旨在加深理解云辐射反馈机制,并为改进模式中云重叠参数化方案提供一定观测依据。

In this study,we temporally and spatially obtain the cloud types from an active sensor product(2BCLDCLASS-LIDAR)and the cloud properties and the associated radiation fluxes at the top of the atmosphere from a passive sensor product(CERES-SSF)(01/2007-12/2010).Further,we statistically and globally analyze the properties and instantaneous radiative forcings of various types of single-and two-layer clouds overlapping with high clouds located at the top of atmosphere.Although the aforementioned two products are independent,the passive sensor results denote reasonable contrasts between various types of single-layer clouds in terms of their optical depth,phases,and other parameters.The differences between the cloud properties of various types of single-layer clouds can significantly affect the radiation budget at the top of the atmosphere.By comparing the distributions of the CERES sample numbers with the short-and longwave radiative forcings of clouds,we denote that their high-value regions differ in terms of the shape,location,and area;further,we indicate the particular radiative characteristics of different single-layer cloud types.The dense area of the CERES-footprint sample number in case of the stratocumulus type cloud is shaped somewhat similar to an ellipsoid,whereas those of the remaining single-layer cloud types tend to resemble an exponential curve.Further consideration of the impacts of the overlapping high clouds reveals that that the overlying high clouds have more opaque and thicker cloud bodies when compared with those contained in single-layer high clouds,that the underlying cloud types tend to be more transparent and thinner when compared with their corresponding single-layer cloud types,and that the two-layer cloud types overlying high clouds,excluding high clouds that overlap cumulus,exhibit weaker cooling impacts on the Earth's atmosphere when compared with those exhibited by their underlying single-layer cloud types.The study results provide a detailed understanding of the cloud-radiation feedback and an observational basis for improving the cloud parameterization schemes in models.