Assessment of marine boundary layer cloud simulations in the CAM with CLUBB and updated microphysics scheme based on ARM observations from the Azores
Assessment of marine boundary layer cloud simulations in the CAM with CLUBB and updated microphysics scheme based on ARM observations from the Azores
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DOI：
10.1002/2016jd025274
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发表时间：
2016-07
期刊：
影响因子：
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通讯作者：
Xue Zheng;S. Klein;Hsi‐Yen Ma;P. Bogenschutz;A. Gettelman;Vincent E. Larson
中科院分区：
文献类型：
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作者：
Xue Zheng;S. Klein;Hsi‐Yen Ma;P. Bogenschutz;A. Gettelman;Vincent E. Larson
为了评估社区大气模式（CAM）三个版本中的海洋边界层（MBL）云模拟，进行了三组短期全球后报，并与2009年6月至2010年12月在亚速尔群岛Graciosa岛的大气辐射测量计划（ARM）观测进行了比较。这三个版本包括CAM5.3与默认方案（CAM5.3），CAM5.3与云层统一的Binormal（CLUBB-MG 1），和CAM5.3与CLUBB和更新的微观物理方案（CLUBB-MG 2）。我们的结果表明，相对于CAM5.3默认方案，模拟与CLUBB更好地代表MBL云底高度，主要云层的高度，和每日云量的变化。CLUBB还更好地模拟了云分数与云液态水路径（LWP）的关系，这很可能是由于CLUBB通过概率分布函数（PDF）方法对这些变量进行了一致的处理。在CLUBB-MG 2的模拟中，云下降水蒸发大大增强，并且根据有限的观测估计，云下降水蒸发更加真实。尽管有这些改进，所有模型版本都低估了MBL云量。CLUBB‐ MG 2减少了云内LWP（云不太亮）的偏差，但由于低估了多云场景的频率，MBL云仍然太少。因此，结合CLUBB和MG 2方案更好地模拟了MBL云过程，但由于偏差仍然存在于MBL云量CLUBB-MG 2并没有改善地面短波云辐射效应（CRESW）的模拟。
To assess marine boundary layer (MBL) cloud simulations in three versions of the Community Atmosphere Model (CAM), three sets of short‐term global hindcasts are performed and compared to Atmospheric Radiation Measurement Program (ARM) observations on Graciosa Island in the Azores from June 2009 to December 2010. The three versions consist of CAM5.3 with default schemes (CAM5.3), CAM5.3 with Cloud Layers Unified By Binormals (CLUBB‐MG1), and CAM5.3 with CLUBB and updated microphysics scheme (CLUBB‐MG2). Our results show that relative to CAM5.3 default schemes, simulations with CLUBB better represent MBL cloud base height, the height of the major cloud layer, and the daily cloud cover variability. CLUBB also better simulates the relationship of cloud fraction to cloud liquid water path (LWP) most likely due to CLUBB's consistent treatment of these variables through a probability distribution function (PDF) approach. Subcloud evaporation of precipitation is substantially enhanced in simulations with CLUBB‐MG2 and is more realistic based on the limited observational estimate. Despite these improvements, all model versions underestimate MBL cloud cover. CLUBB‐MG2 reduces biases in in‐cloud LWP (clouds are not too bright) but there are still too few of MBL clouds due to an underestimate in the frequency of overcast scenes. Thus, combining CLUBB with MG2 scheme better simulates MBL cloud processes, but because biases remain in MBL cloud cover CLUBB‐MG2 does not improve the simulation of the surface shortwave cloud radiative effect (CRESW).