The Spatial And Temporal Distribution Characteristics Of Cloud Macroscopic Vertical Structure In China And Surrounding Areas Based On The CALIOP Observations

Clouds can act as a radiation source,emitting thermal radiation,while also absorbing or scattering shortwave solar radiation and outgoing longwave radiation.Accordingly,they regulate and influence the energy distribution of the earth–atmosphere system,which has an important impact on global climate.Different cloud heights have different radiative effects: the reflectivity of low-level clouds often causes a cooling effect,while high-level clouds heat the earth–atmosphere system via a greenhouse effect.The in-depth study of different cloud heights can therefore help to more fully understand the interactions between clouds and radiation.The CALIOP LIDAR forms part of the CALIPSO platform has a good detection capability,using CALIOP data is feasible for studying the macroscopic vertical structural features of clouds.Based on CAL_LID_L2₀1kmCLay-Standard-V4-10 cloud layer products from June 2006 to May 2016,this study statistically analyzed the horizontal distribution and seasonal variation of cloud vertical structure over China and surrounding areas?0°N–55°N,70°E–140°E?.The content includes: the probability of occurrence of single-layer clouds and multi-layer clouds at different altitudes in China and its surrounding areas,the horizontal distribution of cloud heights and average cloud thickness,and the difference between day and night,as well as statistical analysis of the characteristics of seasonal changes,and at the same time the clouds at different heights The statistical analysis of the correspondence between cloud thicknesses and the main research conclusions are as follows:?1?Regional differences in the occurrence of clouds are apparent throughout the year.Taking 35°N as a boundary,the occurrence of cloud over southern China is greater than over the north,and the occurence of single-layer cloud is higher than that of multi-layer clouds.Single-layer high-level clouds occur most frequently,followed by mid-level,with low-level clouds the least frequent.The double-layer cloud accounts for the largest proportion in the multi-layer cloud system,and the probability of cloud occurrence decreases with the increase of the number of clouds.The horizontal distribution of double-layer clouds and three-layer clouds at different heights has large regional differences.The overall probability of occurrence of monolayer clouds was slightly higher during the day than at night,and the multi-layer cloud as a whole exhibited a day-time difference of 10% to 15% less than the nighttime.?2?The seasonal variation characteristics of cloud occurrence probability are obvious.The occurrence of clear-sky conditions north of 35°N over China is greater than that south of 35°N.Cloud occurrence in summer and autumn is generally greater than in spring and winter.In summer,single-layer high-level clouds and double-layer high-level clouds + high-level clouds,high-level clouds + middle-level clouds and three-layer high-level clouds + high-level clouds + high-level clouds,high-level clouds +high-level clouds + middle-level clouds appear in the main body of the Tibetan Plateau,Maximum probability.In areas northeast China Sea,north of the South China Sea and other areas north of 30°N°,low clouds of single-layer clouds in winter and high clouds + low clouds of double clouds and high clouds + high clouds + low clouds of a small number of three-layer clouds appear The probability is higher than other seasons.?3?There are obvious regional differences in the height of cloud tops and cloud bottoms.The second layer of clouds,the third layer of clouds and the first layer of the cloud in the corresponding area of the height change is more obvious.The thickness of the cloud with the highest probability of occurrence to each region is between 0.3 and 0.6 km.The contribution of clouds with different thicknesses above 0.3 km to the total sample volume decreased with the increase of cloud thickness.?4?The average height of cloud tops and cloud bottoms in each season is basically the same as its horizontal distribution,but the seasonal variation is obvious.In summer,the height of all layers of clouds is the highest,followed by the spring,the autumn is small,and the height of the winter clouds is the lowest.In some areas,there may be some cloud tops or cloud base heights that are greater in spring or winter than in summer.