Temporal And Spatial Distribution Of Cloud Microphysical Parameters And Surface Shortwave Radiation In Qinghai-Tibet Plateau Based On Himawari-8 Satellite Data

Cloud plays an important role in the energy balance and water cycle process of the earth atmosphere system.Its radiative forcing is an important index to analyze the interaction between cloud and radiation and reflect the influence of cloud on the radiation balance of the earth atmosphere system.Cloud radiative forcing mainly depends on its microphysical characteristics,and is an important parameter in the study of cloud radiation climate change.The study of cloud microphysical characteristics and radiative forcing can deepen the understanding of the interaction mechanism between cloud and radiation,and can predict weather and climate change more accurately.The research on the shortwave radiation and cloud microphysical parameters of the Tibetan Plateau is also the focus of the second scientific research project.However,due to the complex topography and meteorological conditions of the plateau,there is a lack of high spatial-temporal resolution ground observation data.The satellite data used are mainly polar orbit satellite products observed once or twice during the day,which makes it difficult to accurately grasp the diurnal and seasonal variation characteristics of key energy balance parameters such as shortwave radiation in the plateau area.The advantage of high spatial and temporal resolution of Himawari-8 new generation geostationary meteorological satellite data provides accurate data for the analysis of spatial and temporal changes of key parameters of energy cycle in scientific research projects,and provides important information for the analysis of spatiotemporal variation characteristics of key parameters of energy balance in the second scientific research project of Qinghai Tibet plateau.In this study,the cloud microphysical parameters of Himawari-8 new generation geostationary meteorological satellite products and surface downward short wave radiation data products are used.Firstly,the reliability of the products is evaluated with the ground-based station data in the Qinghai Tibet plateau area,and then the temporal and spatial distribution characteristics of cloud microphysical parameters and surface downward short wave radiation characteristics are analyzed.At the same time,the diurnal and seasonal variations of short wave radiative forcing over the plateau are analyzed and evaluated by using CERES and ERA5 meteorological reanalysis data.The main conclusions are as follows:(1)The short wave radiation over Qinghai Tibet Plateau is higher in spring and summer than in autumn and winter,and the radiation duration in spring and summer is longer than that in autumn and winter.The highest value is in the southwest of the plateau,and the lowest value is in the southeast,which is higher in the West and lower in the East,and gradually decreases from the high altitude area in the southwest to the southeast.The shortwave radiation is the strongest in all seasons from 11:00 to 13:00local time,and the diurnal variation shows the characteristics of increasing and then decreasing.The accuracy verification of Himawari-8 data,ERA5 reanalysis data and surface shortwave radiation of CERES satellite products and ground-based stations show that CERES data has high accuracy and low spatial resolution;REA5 data has high resolution but underestimation;Himawari-8 data has high precision and high spatial resolution.(2)Based on the Himawari-8 data,the cloud optical thickness over the Tibetan Plateau shows the seasonal variation characteristics of high in summer and low in winter,and the regional difference is small.In spring,it is lower in the southwest,higher in the East,lower in Qaidam Basin and higher in Sichuan Basin.The cloud coverage period in summer is longer than that in the other three seasons,and the cloud coverage rate in spring and autumn has an obvious increasing trend.In spring,the effective radius of cloud particles in the central and eastern regions of the Qinghai Tibet Plateau is larger than that in the southwest.In summer,it increases from south to north.In autumn,it is larger in the East and smaller in the west,and generally smaller in winter.The effective radius of ice cloud particles is larger in spring and summer than in autumn and winter,and the effective radius of ice cloud particles in winter is slightly higher than that in autumn.The LWP in the Qinghai Tibet Plateau is higher in the northeast and lower in the southwest.It is higher in spring and summer than in autumn and winter.The trend of ice cloud water path is consistent with optical thickness and effective particle radius,but the water path of ice cloud has obvious seasonal variation characteristics of more in spring and summer,less in autumn and winter.(3)The plateau as a whole is a transitional region of positive and negative values of cloud short wave radiation forcing,and there are obvious seasonal differences and regional division in this transition.According to the results of ERA5 and CERES data,the cooling effect in the southeastern part of the plateau is stronger,and the cooling effect increases from the western region to the southeast region.In winter,the greenhouse effect of cloud is greater than the reflectivity effect of cloud,and the cloud plays a role of radiative warming to the earth atmosphere system.In spring,summer and autumn,on the contrary,clouds have a radiative cooling effect on the earth atmosphere system.In terms of numerical value,the negative value is more in spring,summer and autumn,and the positive value is more in winter.