| Ice clouds have a large impact on the hydrological systems and Earth's energy budget.Comparing to water clouds,the formation and growth processes of ice clouds are more complicated and not fully understood yet.The interaction between aerosol and clouds also has an important impact on the climate system and a challenge in current climate research.Previous studies have discussed the interaction between aerosol and water clouds,and the influence of aerosol on ice clouds has not been considered more.In this paper,the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation(CALIPSO)ice clouds product level-3 data(CAL?LID?L3?Ice?Cloud)?aerosol product level-3 data(CAL?LID?L3?APro)and moderate resolution imaging spectroradiometer(MODIS)cloud product level-3 data(MOD08?D3)is employed to analyze the horizontal and vertical distribution of heterogeneous ice clouds over East Asia from January 2010 to December 2016.the vertical distributions of ice clouds top properties in summer of 2017 are analyzed using the Advanced Himawari Imager(AHI)/Himawari-8(HW8)cloud products.Heterogeneous ice clouds must have ice nuclei involved in the formation and formation temperature is above-40 °C.The results show that the differences in the fraction of ice clouds in northern and southern East Asia are related to temperature,radiation and ice nuclei from the ground.In northern East Asia,the horizontal distribution of the fraction of ice clouds between-40 and 0 °C is about 30% higher than in southern East Asia.The average height of ice clouds in southern East Asia is higher than that in northern East Asia,the ice clouds in the north are closer to the ground and affected by the surface ice nuclei.The ice clouds formation process is more promoted in northern East Asia than in southern East Asia.A weak increased(about 5%)fraction of ice clouds is observed in northern East Asia in the cloud bins temperatures range from-30 to-10 °C.At this temperature,the process of contact freezing and immersion freezing forms ice particles.The results indicate that these formation processes are promoted in the north.The fraction of ice cloud bins in the troposphere(below 10 km)was larger in northern East Asia than in southern East Asia.The fraction of ice clouds between the north and the south shows a peak at around 6 km,about 50%.ice clouds occur most frequently in the Tibetan Plateau and the South Asian monsoon region with the frequency of occurrence can reach more than 50%.There is a steep gradient of ice clouds occurrence frequency extending from southern to northern East Asia.The vertical distributions of ice clouds top are highly dependent on latitude,in addition to the important roles of terrain,land-sea thermal contrast,and monsoons.In the Tibetan Plateau,the frequency of ice clouds top is maximum at 6 to 9 km,and in the monsoon region,ice clouds are widely distributed between 6 and 15 km.The frequency of ice clouds near Japan between 9 and 12 km is large due to the effect of Kuroshio.The temperature of the ice clouds top is bounded by 42°N,and there is a significant difference between the north and the south.In the vertical distributions,among the ice cloud occurrence frequencies in the nine study areas,the Tibet Plateau and the monsoon region are consistent with the above studies,and the eastern part of East Asia is lower than other research areas.The radius of ice cloud particles shows a trend of increasing first and then decreasing with height.The radius of ice cloud particles is the largest relative to other research areas over the ocean area.The double-peak structure of ice cloud optical thickness exists in western East Asia,in other relatively flat areas,there is only one single peak.In the Tibet Plateau,there is a higher ice cloud optical thickness between 6 and 15 km,and the ice cloud thickness of the Bay of Bengal is greater at 12 to 15 km.The latitude is closely related to the distribution of ice clouds.There is a maximum number of ice cloud samples in the high altitude area near the tropics.As the latitude increases,the maximum number of ice cloud samples and the height of the maximum number are gradually decreasing.Moreover,there is a different ice cloud samples between the northern and southern hemispheres.Aerosol have a maximum near the low latitude ground that is symmetrical at the equator.Aerosol can develop to about 5 kilometers in the northern hemisphere,while the southern hemisphere is about 3 kilometers.The trend of aerosol is consistent with ice clouds,there is an inverse relationship between ice water content and effective radius of ice cloud with time,the trend of aerosol do not correspond well to ice water content and effective radius of ice cloud.The clean area show a large aerosol optical thickness due to the effect of sea salt particles,but this does not affect the smaller ice cloud optical thickness in the clean area.Aerosol promotes ice cloud formation from 0 °C to-10 °C and-20 °C to-40 °C.As the temperature decreases,the ice water content and the effective radius of ice cloud increases.in the contaminated area,the ice water content and the effective radius of ice cloud is smaller than the clean area. |
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