Gaoyuan qixiang (Jun 2022)
Comparative Analysis of the Total Cloud Cover Products of Various Data in China
Abstract
Cloud is an important factor affecting climate change， and it plays an important role in controlling the earth's energy and water cycle.A comprehensive understanding of the distribution and changes of the total cloud cover is particularly important for assessing the role of cloud in climate change.At present， there are relatively few studies on the characteristics of cloud cover changes in China based on reanalysis data.Further attention needs to be paid to the application of cloud products based on reanalysis data in China.Using the total cloud cover data of 776 sites observations in Mainland China， the four sets of CRA40， ERA5， JRA55， CFSR reanalysis data and the monthly average total cloud cover data of the International Satellite Cloud Climatology Project （ISCCP） from 1987 to 2016， We analyzed the temporal and spatial differences of the total cloud cover of different data in China and the relative consistency between the data.The results showed that： the spatial distribution characteristics of the total cloud cover of different data were generally consistent， and the high value area and low value area of the cloud amount were reflected.However， there were certain differences in the value of the different data.The total cloud cover of ISCCP was generally 5%~20% higher than other data， and the various data were in better agreement in the high value areas of total cloud cover such as Jianghuai， Southeast and Southwest.In the Northeast， Northwest and most areas of Inner Mongolia， due to the snow cover， the misjudgment of cloud and snow in satellite inversion resulted a significantly higher ISCCP total cloud content compared with ground observations and reanalysis data.CRA40 and JRA55 had relatively small deviations from ground observations in Northeast， North China and Jianghuai regions.ERA5 and CFSR were closer to ground observations in South China and Southwest China.JRA55 total cloud cover was the lowest among the various data.This was particularly evident in the North China， Northwest China and Qinghai-Xizang Plateau.ERA5 had the highest consistency with ground observations， and its correlation coefficient reached 0.91.The correlation coefficient between reanalysis total cloud cover and ISCCP was lower than 0.7， while the correlation coefficient between CRA40 and ERA5 reaches 0.87.CFSR and ERA5 also had a high correlation.JRA55 and CFSR had a very low correlation.Next， we can introduce more data and different parameters such as high， medium， and low cloud cover for more detailed analysis.
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