Application Of Cloudsat Data In The Study Of Rainfall Clouds Over Tianshan Mountains

The spatial and temporal distribution of clouds, together with cloud interior structure and evolution of cloud systems have become important frontwards subjects in atmospheric remote sensing, weather forecasting and climate prediction research. As increasingly more environmental and meteorological satellites being sent up, it seems to be possible that revealing the properties of macro and micro precipitation clouds and the relationship between clouds and precipitation. In this paper, the data from Aqua and CloudSat of A-train satellite constellation were employed. Firstly, the total cloud amount and characteristics of lower layer cloud parameters in Xinjiang were analyzed, in order to draw the spatial and temporal distribution of clouds based on Aqua observation. Then,8 rainfall episodes around Tianshan Mountains were selected using data from CloudSat and ground rainfall observation. The vertical distribution of ice water content, ice effective radius and ice number concentration of those episodes were analyzed. In addition, the relationship between the three ice cloud parameters and preciptation were also evaluated. And the results as the following:1.The distribution of total cloud amount and lower layer cloud properties are very different in different places in Xinjiang. The annual variation of total and lower layer cloud amount over the three Mountain ranges were similar, which were higher in spring and summer but lower in winter. Also the correlation between the 5-year monthly averaged amount of total and lower layer clouds were estimated, which turned out to be significantly correlative. The ice water path was higher in spring and summer but lower in winter, compared to highest liquid water path in winter. Annual variation of water particle radius of lower layer clouds over the three mountain ranges were similar too, which were lower in summer and autumn but higher in winter; and the fluctuation range were less, the difference between min and max 5-year monthly averaged values were also small. Annual variation amplitude of ice particle effective diameter over Tianshan Mountains and Altay Mountains were small, but greater over Kunlun Mountains, where ice particle effective diameter reduced rapidly in August. The lowest values of water particle radius and ice particle effective diameter both appeared in August. Because of effect of different Altitudes, the effective height of lower layer clouds over Kunlun Mountains was highest, followed by that over Tianshan Mountains. No matter cloud amounts or liquid water path or particles size of lower layer clouds, the highest multi-year averaged values all distributed in Tianshan Moutains.2. The top and bottom of rainfall cloud level are the low value areas of ice water content, and middle of cloud level are high value areas, whose high value areas are at the height of 6-7km. the heights of peak values are different. The smaller the ice water content range, the greater the occurance.High values of the ice effective radius were at the bottom of the clouds, which were smaller with the increase of height. The ice effective radius at the range of 500-1000μm rank in the first place, especially those whose equivalent radius at the range of 500-800μm, and those whose radius greater than 1500μm are no more than 1%.The high value of ice number concentration appear in the upper and middle of clouds and the low value areas appear in the bottom of clouds, ice number concentration increase with the increased vertical height of cloud. In the 8 rainfall processes, ice number concentration during 3 processes are ranging from 0-3513 L-1, the ones during another 2 processes are ranging from 0-20000 L-1 and the ones during the rest 2 processes are ranging from 0-1500 L-1.3.Take Pearson's correlation coefficient(rp) to evaluate correlations between rainfall and ice water content or ice effective radius or ice number concentration, the result turned out that correlations between ice water content(IWC) or ice number concentration(INC) and ground rainfall were low, but significant between ice effective radius(IER) and rainfall. When considering cloud height from 4km to 9km in altitude, the correlations between IWC or IER and rainfall were better, which reduced gradually as cloud layer become higher; the correlations INC and rainfall in the middle and upper layer of clouds were higher than in lower layer clouds.