CloudSat/CALIPSO卫星资料分析云的全球分布及其季节变化特征

Global distribution and seasonal variation of clouds observed from CloudSat/CALIPSO

  • 摘要: 全球气候模式(GCM)中云的参数化方案具有不确定性,了解云的时、空变化能为参数化方案提供有效参考。利用搭载在属于A-Train卫星序列的CloudSat和CALIPSO上的94 GHz云廓线雷达(CPR)以及正交极化云-气溶胶激光雷达(CALIOP)联合的2级云分类产品,分析了2007年3月-2010年2月8种云类及三相态的云量地理分布、纬向垂直分布的季节变化特征以及云层分布概率。结果发现,卷云的分布体系与深对流云相似,主要集中在西太平洋暖池、全球各季风区及赤道辐合带,分布格局与气压带、风带季节性移动一致。层云与层积云主要分布在中低纬度非季风区以及中高纬度的洋面上。高积云与高层云的分布形成明显的海陆差异,雨层云与积云的分布形成明显的纬度差异。冰云分布与卷云相似,云高随纬度递增而递减;水云分布与层积云相似,平均分布于2 km高度;混合云集中于高纬度地区及赤道辐合带,中纬度地区随纬度变化集中于海拔0-10 km的弧形带。层状云多以多层云形式出现,积状云多以单、双层云的形式出现,层状云的云重叠现象比积状云更显著。积状和层状云的分布特征与积云和层云降水的分布特征基本一致,验证了不同类型降水的卫星观测结果,同时为气候模式的云量诊断方案提供对比验证的数据。

     

    Abstract: The significant uncertainties in cloud parameterization in multiple global climate models (GCMs) need to be addressed based on better understanding of temporal and special variation of clouds. Global and zonally averaged vertical distributions of cloud occurrence frequency of eight cloud types in three phases and their seasonal variations obtained from the combined CloudSat radar and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar measurements from March 2007 to February 2010 are investigated. The global distribution pattern of cirrus is found to be similar to that of deep convective clouds, which are mainly distributed over the warm pool of the West Pacific, the monsoon region and the intertropical convergence zone (ITCZ). The seasonal pattern of cirrus and deep convective clouds vary with pressure and wind zone. Stratocumulus and stratus are largely located over non-monsoon regions in the middle and low latitudes and over the oceans in high latitudes. Altocumulus and altostratus show obvious difference between land and sea. Cumulonimbus and cumulus exhibit distinct differences between the high and low latitudes. The spatial pattern of ice phase clouds is similar to that of cirrus while the pattern of water phase clouds is similar to that of stratus and stratocumulus. Zonally averaged vertical distribution of clouds indicates that the average cloud top of ice phase clouds decreases with increasing latitude. Water phase clouds are located in low altitudes (about 2 km). Mixed phase clouds are mainly found over an arcuate zone ranging from 0-10 km. Stratiform clouds have a higher probability to display a multiple-layer structure, while convective clouds are prone to form as single-layer cloud clusters. Cloud overlapping is more obvious for stratiform clouds than for convective clouds. Distributions of cumuliform and stratiform clouds are consistent with distributions of convective and stratiform precipitation. These results are valuable for evaluation of cloud diagnostics in global and regional climate models.

     

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