Study On Cloud Features Over Qilian Mountains And Central Gansu Based On Satellite Remote Sensing

By using CloudSat and CALIPSO satellite remote sensing data from 2007 to2010 and surface precipitation data provided by China National Meteorological Information Center(CMDC)from 1996 to 2016,the characteristics of different cloud types in Qilian Mountains,central Gansu and Shiyang River Drainage Basin were analyzed,as well as cases analyzed of the characteristics of cloud.The results show that:The seasonal variation of total cloud fraction in each research area is very consistent,the larger values are more than 70% in spring and summer.The high values area of total cloud fraction are mainly concentrated in the southern slope of Qilian Mountains,which is consistent with the high precipitation values area.The maximum value of cumulus cloud fraction occurs in summer,and the precipitation frequency of cumulus cloud is higher than that of Stratiform cloud.The cloud is dominated by single-layer cloud,and the thickness of single layer cloud is over 2.0km.The maximum thickness of single-layer cloud is 3.0 km in spring in central Gansu.The thickness of two-layer clouds is thicker than that of three-layer clouds.Cumulus cloud and single-layer cloud which produce precipitation occur more frequently.The trend of cloud frequency altitude distribution in each research area is similar,Stratiform cloud ranged from 500 m to 12 km above the surface,and the peak frequency appeared around 6 km in height.The altitude distribution of cumulus cloud frequency is obviously lower than that of Stratiform cloud,and the peak value appears around 1.5 km in height.The liquid water content of cumulus cloud is higher than that of stratiform cloud at all altitudes.The maximum liquid water content appears below 1.0 km,and the liquid water content decreases rapidly from the bottom to the top until it decreases slowly around 1.0 km.Ice water content extends higher than liquid water content.Vertical distribution of ice water content in stratiform and cumulus cloud is mostly single-peak type.Except summer,the extension height and peak height of ice water content in stratiform cloud are higher than those in cumulus cloud.In autumn,aircraft operating height of stratiform clouds in central Gansu should be more reasonable at3.0 km;In spring,aircraft operating height of stratiform clouds in Shiyang River Drainage Basin should be more reasonable at 2.2 km.The liquid effective radius of non-precipitation cloud is uniform in the upper and lower altitudes,which is smaller than that in precipitation cloud.The liquid effective radius of precipitation cloud decreases rapidly from the bottom to 3~4 km,and the bottom particles are larger than the upper ones.Ice particles below 3.0 km in non-precipitation cloud tend to rise and large particles above 3.0 km tend to sink.The ice effective radius of precipitation cloud decreases rapidly with the increase of altitude,the value of bottom layer is much larger than that of non-precipitation cloud bottom layer,it reflects that large particles in precipitation cloud sink under the influence of gravity.Precipitable nimbostratus cloud have a low cloud base height of about 1 km,and the development of cloud layer is deeper than that of non-Precipitable.The maximum area of ice water content occurs mainly in the upper and middle parts of cloud,concentrated maximum regions exist in precipitation cloud.There is a structure of upper cold and lower warm in precipitable nimbostratus cloud.In each case,the maximum of ice water content appeared in the upper and middle part of the cloud,but the maximum ice effective radius appears in the lower part of the cloud,it shows that the ice particles in the upper and middle part is small and the number of ice particles is large;The ice particles in the lower part is larger,but the number is relatively scarce.