基于CloudSat-CALIPSO资料的北极云宏观特征及形成机制研究北大核心CSCD

基于CloudSat-CALIPSO(CloudSat-Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations)卫星反演资料以及ERA5(ECMWF Reanalysis v5)月平均再分析资料,分析了北极地区总云量及其出现频率最高的层积云(Sc)的时空分布特征,并且探讨了层积云形成的可能原因。分析结果表明:秋季是北极地区全年总云量最多的季节,且喀拉海—楚科奇海区域云量增加幅度较为明显,其中海气温差较大、表面潜热通量致使边界层上升运动较强且相对湿度大是该区域云形成和维持的主要因素。另外,北极地区分布着大量Sc,主要位于常年几乎无海冰覆盖的挪威海—巴伦支海区域。此区域的低层稳定度与Sc云量呈负相关,即低层稳定度越大,Sc云量越少,此现象与热带以及中纬度等地区不同。开阔的海洋表面通过地表—大气耦合、热量和湿度的湍流表面通量降低了低层稳定度,促进了层积云的形成,增加了层积云的覆盖。

Macroscopic Characteristics and Formation Mechanisms of Arctic Clouds Based on CloudSat-CALIPSO Data

On the basis of CloudSat-CALIPSO (CloudSat-Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite inversion data and ERA5 (ECMWF Reanalysis v5) monthly average reanalysis data, the temporal and spatial distributions of the total cloud amount and stratocumulus clouds (Sc) with the highest frequency in the Arctic are analyzed, and the possible reasons for the formation of Sc are discussed. The results show that the total cloud amount in the Arctic region is the largest in autumn, and the increase in cloud amount is more obvious in the Kara Sea–Chukchi Sea region. Factors such as the relatively large sea–air temperature difference, strong upward movement of the boundary layer forced by the surface latent heat flux, and high relative humidity are the main causes of cloud formation and maintenance in this area. In addition, a large amount of Sc is observed in the Arctic, mainly in the Norwegian Sea–Barents Sea, which is almost without sea-ice cover all year round. The lower tropospheric stability (LTS) in this area is negatively correlated with the amount of Sc. The greater the LTS is, the smaller the amount of Sc. This phenomenon is different from what is observed in tropical, mid-latitude regions. The factors affecting the formation of Sc in this sea area can be attributed to the open ocean reducing the LTS through surface–atmosphere coupling and the turbulent surface flux of heat and humidity, which promote the formation of Sc and increase the coverage of Sc.