The Mean Climate of the Community Atmosphere Model (CAM4) in Forced SST and Fully Coupled Experiments
The Mean Climate of the Community Atmosphere Model (CAM4) in Forced SST and Fully Coupled Experiments
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DOI：
10.1175/jcli-d-12-00236.1
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发表时间：
2013-07-01
影响因子：
4.9
通讯作者：
Zhang, Minghua
中科院分区：
文献类型：
--
作者：
Neale, Richard B.;Richter, Jadwiga;Zhang, Minghua
社区大气模式第4版（CAM4）是社区气候系统模式第4版（CCSM4）的一部分。由于有限体积（FV）动力核心具有优越的传输和守恒特性，因此其现已成为默认值。上级。深对流参数化的变化包括对流可用位能（CAPE）的稀释羽流计算和对流动量输送（CMT）的引入。在宏观物理状态更新之后，现在进行额外的云分数计算，以提供改进的热力学一致性。在非常干燥的环境中，对云分数计算进行了进一步的冷冻干燥修改（例如，例如，在一个实施例中，北极），其中云分数和云水值往往是不一致的CAM3。在CAM4中，FV动力核心进一步降低了过度的信风模拟，但减少了高纬度地区的纬向应力误差。羽稀释减弱了对流层中层热带干偏置，并减少了阿拉伯半岛和南印度洋上空持续季风降水偏置。CMT减少了东部海洋盆地过度的信风偏差。与CAM 3相比，CAM 4显示出云分数的整体减少，这主要是由于冷冻干燥和改进的云分数平衡修改。区域气候特征的改善包括定常波从太平洋向中纬度的传播和北方半球阻塞事件的季节性频率。FV动力核心的1度与2度水平分辨率在降水和地面应力的区域气候特征方面表现出上级改进。CAM3和CAM4之间完全耦合的平均气候的改善也比强迫海表温度（SST）模拟更显着。
The Community Atmosphere Model, version 4 (CAM4), was released as part of the Community Climate System Model, version 4 (CCSM4). The finite volume (FV) dynamical core is now the default because of its superior transport and conservation properties. Deep convection parameterization changes include a dilute plume calculation of convective available potential energy (CAPE) and the introduction of convective momentum transport (CMT). An additional cloud fraction calculation is now performed following macrophysical state updates to provide improved thermodynamic consistency. A freeze-drying modification is further made to the cloud fraction calculation in very dry environments (e. g., the Arctic), where cloud fraction and cloud water values were often inconsistent in CAM3. In CAM4 the FV dynamical core further degrades the excessive trade-wind simulation, but reduces zonal stress errors at higher latitudes. Plume dilution alleviates much of the midtropospheric tropical dry biases and reduces the persistent monsoon precipitation biases over the Arabian Peninsula and the southern Indian Ocean. CMT reduces much of the excessive trade-wind biases in eastern ocean basins. CAM4 shows a global reduction in cloud fraction compared to CAM3, primarily as a result of the freeze-drying and improved cloud fraction equilibrium modifications. Regional climate feature improvements include the propagation of stationary waves from the Pacific into midlatitudes and the seasonal frequency of Northern Hemisphere blocking events. A 1 degrees versus 2 degrees horizontal resolution of the FV dynamical core exhibits superior improvements in regional climate features of precipitation and surface stress. Improvements in the fully coupled mean climate between CAM3 and CAM4 are also more substantial than in forced sea surface temperature (SST) simulations.