| As an important boundary line between the north and south geographical environment of China,and as the transition zone between the warm temperate zone and the northern subtropical zone,the Qinling Mountain,has a large difference in climate and generally presents a spatial pattern of "southern humid north drought".its climate change is very sensitive.In recent years,the "middle line of South-to-North Water Diversion Project" and "Hanjiang to Weihe River Project" have been implemented,the purpose of these projects is to transfer the water from the upper reaches of the Hanjiang to the Beijing-Tianjin and Guanzhong areas.In the context of global warming,as the water producing area of the Hanjiang,the Qinling Mountain,its precipitation is more complicated.A lot of literatures have analyzed in detail the variation characteristics of precipitation in the north and south of the Qinling Mountain,but as a precondition for precipitation,the cloud lacks detailed analysis of its characteristics,especially the macroscopic and microscopic physical characteristics and radiative forcing characteristic of the cloud in the north and south of the Qinling Mountain.Analysis of the characteristics of the cloud will help to understand the precipitation nature and precipitation formation mechanism of the region,and provide scientific basis for rational implementation of water resources allocation.Based on the CloudSat satellite products from 2007 to 2015 and ERA-Interim reanalysis data,this paper analyzes the macroscopic and microscopic physical characteristics and radiative forcing characteristic of cloud in the north and south of the Qinling Mountain.The results show that:(1)The occurrence frequency of total cloud in the north and south of the Qinling Mountain is between 50%and 75%,the winter half year is less than the summer half year,the mid cloud and low cloud are dominant clouds.The distribution height of the cloud is basically below 15km,the low cloud is mainly below 3 km,the mid cloud is mainly in 3-7 km,and the high cloud is mainly in 7-12 km.Four seasons in all regions are dominated by cloud-days,the total cloud occurrence frequency is high in the south,but low in the north,and gradually decreases from south to north.Seasonal variation of cloudlayer height in the north and south of the Qinling Mountain,Guangzhong region is the most significant in single-layer cloud,while Shannan in the multi-layer cloud.The thickness of clouds in each region is 1?3 km,there is no obvious seasonal characteristics in cloud thickness.Except for a few cases,occurrence frequency of eight major clouds in different regions has significant seasonal variations.(2)The radar reflectivity of cloud is mainly between-30?10 dBz,and is distributed at a height below 15 km.The profile of the cloud water path and the cloud water content are both high in the south and low in the north,and especially the most obvious in summer.This distribution trend reflects the hindrance of the Qinling Mountain to water vapor.The spatial distribution of the microphysical parameters of the cloud is consistent with th?-e its occurrence frequency,both of which are high in the south and low in the north.The average liquid water content is 160 mg/m3,and the ice water content is 45 mg/m3,the total water content is dominated by liquid water content.Liquid water effective radius is mainly concentrated in 5?15 um,and the maximum value(12.1 um)appears in the winter of Shannan.Ice water effective radius is mainly distributed below 100 um,the highest in summer and the lowest in winter,which decreases with height.The seasonal variations of liquid water number concentration in Guanzhong and Qinling regions are relatively significant,but in Shannan is not obvious.In Guanzhong and Shannan,the maximum of ice water number concentration appeared in the summer,while the maximum of Qinling area appeared in the autumn.In the probability density distribution figure(PDF),except for the liquid water number concentration,the distribution of other parameters is unimodal.(3)In the process of heavy precipitation,the main clouds in north of the Qinling Mountain are As,Ac and Dc,the occurrence height is between 1-11.4 km,and the thickness 10.4 km;The main cloud in south of the Qinling Mountain is As,its appearance height is 2-9 km,and the thickness is thinner than the north(6.8 km).Due to the different type of clouds,the microphysical characteristics of cloud in the north and south of the Qinling Mountain are different.The average liquid water content in the north of Qinling Mountain is 99.9 mg/m3,which is concentrated in the 0-100 mg/m3 range of the mid and upper part of the cloud layer.The average value in the south of Qinling Mountain is about twice that of the north,>100 mg/m3 accounts for about 80%and is concentrated in the middle of the cloud layer.In the north of the Qinling Mountain,the liquid water effective radius is mostly concentrated at 5-10 um.In the south of the Qinling Mountain,the liquid water effective radius is mainly 10-15 um and concentrated in the middle and upper middle part of the cloud layer.The liquid water number concentration in the north of the Qinling Mountain is mainly 25-50 cm-3,which is distributed in the middle of the cloud layer.The liquid water number concentration in the south of the Qinling Mountain is mainly in the range of>50 cm-3,which is distributed at a height of 5.5-7.5 km.The ice water content is mainly distributed at 0-50 mg/m3,and the ice water effective radius is mainly 50-100 um.The main distribution height is higher in the north than in the south.The ice water number concentration is mainly 0-100 L-1,and is Mainly distributed at a height of 5.5-7.5 km.(4)The values of long-wave,short-wave and net radiative forcing of cloud in the north and south of the Qinling Mountain are in the range of 35?60 W/m2,-300?-111 W/m2 and-250?-50 W/m2 respectively.The net radiative forcing of cloud is mainly determined by short-wave radiative forcing,and it has a cooling effect on the ground.The long-wave,short-wave and net radiative effects are all higher in the south than in the north,but the trend of short-wave and net radiative forcing is more obvious in the north than in the south,while the long-wave radiative forcing is more obvious in the south than in the north.The annual variation of the cloud radiation effect in the north and south of the Qinling Mountain and the three sub-regions shows that the short-wave and net radiative effects increase with time,and the long-wave radiative effect shows a slight weakening trend wite time.The radiative effects of the three types of clouds are the strongest in the low cloud and the weakest in the high cloud.The change trend of short-wave and net radiative forcing of high cloud and low cloud is more obvious in the north than in the south,and long-wave radiative forcing is the opposite.The short-wave and net radiative forcing of mid cloud have the most significant change trend in Shannan,and the long-wave radiative forcing is the most significant in Qinling. |
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