Study of Climate Change Mechanism in Cloud-Capped Planetary Boundary Layer over the Arctic Ocean Using a Hierarchy of Models Resolving Cloud Formation Processes

本项目是对低层状云的辐射、微物理和动力学性质的研究，目的是改进在不同云条件下大气环流模式(GCMS)中辐射传输的处理方法，并改进GCMS中云形成和云性质的参数化。北冰洋地区的特点是低云(“北极层”)，尤其是在夏季。这些低云影响了自由大气和海冰表面的辐射收支。它们的结构是热量和水汽进入北极的大规模输送、边界层湍流的宏观物理过程以及液态水滴的微观物理和光学性质相互作用的结果。在这个项目中，辐射云强迫和动量、热量和水汽的传输将使用最近开发的具有显式云微物理公式的三维大涡模拟模式来模拟。通过在云层顶部附近引入自适应网格，并采用两流辐射方案来参数化云的不均匀性及其对辐射场的影响，对模式进行了扩展。

This project is a study of the radiative, microphysical, and dynamic properties of low stratiform clouds with the objective of improving the treatment of radiative transfer in general circulation models (GCMs) under varying cloud conditions, and to improve the parameterization of cloud formation and cloud properties in GCMs. A low overcast ("arctic stratus") is characteristic of the Arctic Ocean region, particularly in summer. These low clouds affect the radiation budget of both the free atmosphere and the sea ice surface. Their structure results from an interaction among the large-scale transport of heat and moisture into the Arctic, the macrophysical processes of boundary layer turbulence, and the microphysical and optical properties of liquid water droplets. In this project radiative cloud forcing and the transport of momentum, heat, and moisture will be modeled using a recently developed three-dimensional large eddy simulation model with explicit formulation of cloud microphysics. The model will be extended by introducing an adaptive grid near the top of the cloud layer, and adapting a two stream radiative scheme to parameterize cloud inhomogeneities and their effect on the radiation field.