基于CALIPSO卫星产品的中国区域异质核化冰云比例差异

Differences in the fractions of heterogeneous ice clouds over China based on CALIPSO data

利用2012年1月~2015年12月CALIPSO冰云3级月平均产品(CAL_LID_L3_Ice_Cloud)对中国区域异质核化冰云比例进行分析,研究冰云的比例分布与季节变化特征,探究中国区域冰云分布情况和影响冰云分布的因素。结果表明:中国南北部冰云的比例差异与地面2 m温度、地表长波净辐射通量和来自地面的冰核有关。-40~0℃之间的冰云比例水平分布,中国大陆北部比中国大陆南部高约30%,季节性变化规律明显,冬季南北差异大,夏季南北差异小;云箱温度在-30~10℃之间的冰云,中国大陆北部比例比大陆南部平均高出约5%,春季、秋季、冬季北部冰云比例均高于南部,夏季温度在-8℃以下,南部的冰云比例超过了北部的冰云比例;在对流层(10 km以下),冰云比例分布中国大陆北部比南部高,南北部之间冰云比例差异在6 km左右显示出峰值,约50%,四季冰云比例随高度增加均呈现增大的趋势,且北部冰云比例均高于南部。

Ice clouds have a large impact on Earth’s hydrological systems and energy budget.The formation and growth processes of ice clouds are more complicated than those of water clouds and are not yet fully understood.To investigate the distribution of ice clouds in China and the factors affecting this distribution,this paper analyzes the horizontal and vertical distribution and seasonal variation of the fraction of heterogeneous ice clouds over China from January 2012 to December 2015.Heterogeneous ice clouds must have ice nuclei involved in their formation and formation temperatures greater than-40℃.This paper uses the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation(CALIPSO)level-3 ice clouds data product(CAL_LID_L3_Ice_Cloud)to analyze the horizontal and vertical distribution of heterogeneous ice clouds over China from January 2012 to December 2015.Seasonal ice cloud variation is studied as well.Because of the thin optical depth and high altitude of ice clouds,aircraft and ground-based RSobservations are difficult.However,satellites are a useful tool for detecting ice clouds.In this study,China is divided southern and northern areas based on differences in the fraction of ice cloud distribution.The results of this study show that the differences in the fraction of ice clouds in northern and southern China are related to temperature,radiation,and ice nuclei from the ground.In northern China,the horizontal distribution of the fraction of ice clouds between-40 and 0℃is approximately 30%higher than in southern China.The average height of ice clouds in southern China is higher than that in northern China;however,ice clouds in the north are closer to the ground and thus more affected by surface ice nuclei.The ice cloud formation process is promoted more in northern China than in southern China.Additionally,there is an obvious seasonal variation of the fraction of ice clouds.The difference between northern and southern China is large in winter but small in summer.A weak increased(approximately 5%)fraction of ice clouds is observed in northern China in the cloud temperature bin that ranges from-30 to-10℃.In this temperature range,the contact and immersion freezing processes form ice particles.The results of this analysis indicate that these formation processes are promoted in the north.In the spring,autumn,and winter,the fraction of ice clouds in the north is higher than in the south.In summer,the fraction of ice clouds below-8℃in the south exceeds that in the north.The fraction of ice cloud bins in the troposphere(below 10 km)was larger in northern China than in southern China andthe fraction of ice clouds between the north and the south shows a peak at around 6 km,about 50%.The fraction of ice clouds in northern and southern China was lowest in summer and highest in winter.