Temporal And Spatial Variation And Attribution Analysis Of Downwelling Shortwave Radiation In The Yunnan-Guizhou Platea

Downward Shortwave Radiation(DSR)is a major component of solar radiation,an important parameter for surface radiation balance and energy balance,and a key input parameter for land surface process models and regional climate models.DSR plays an important role in the energy cycle,hydrological cycle,and carbon cycle.Therefore,the DSR reaching the land surface is particularly important for terrestrial ecosystems and human society.The Yunnan-Kweichow Plateau is sensitive to climate change,and the spatial and temporal variation patterns of DSR are not yet clear.The study of spatial and temporal variation of DSR and the attribution analysis over the Yunnan-Kweichow Plateau can help to comprehensively understand the radiation variation in the plateau region and the response magnitude of global climate change,and provide theoretical basis for dynamic monitoring of global climate change and carbon cycle.In addition,DSR is affected by atmospheric conditions(aerosol optical thickness,cloud optical thickness,effective radius of cloud particles,atmospheric water vapor content,ozone content,etc.)and surface conditions(surface albedo,surface elevation),so this paper develops an attribution analysis of DSR variations over the Yunnan-Kweichow Plateau.This paper mainly takes Global Land Surface Satellite(GLASS)products as the main data source,and selects the downward shortwave radiation(DSR)dataset of GLASS.Combining the methods of Theil-Sen Median trend analysis and Mann-Kendall test analysis to study the trends of DSR and its drivers on different time scales;the periodicity of DSR at different time scales is analyzed by wavelet analysis;the correlation between the long time series drivers and DSR at different time scales is simply analyzed by using Pearson correlation coefficient;the number and timing of breakpoints in the trend component and seasonal component of daily averaged DSR were analyzed using Breaks for Additive Seasonal and Trend(BFAST)algorithm;finally,the explanatory power of 11 driving factors(temperature,precipitation,10 m wind speed,aerosol optical thickness,total cloudiness,climate zoning,elevation,slope,aspect,longitude,latitude)were analyzed in combination with the Geodetector model.The main findings are as follows:(1)The annual averaged DSR was 176.7 W·m-2 over the Yunnan-Kweichow Plateau from 1984 to 2018.The radiation intensity of the annual averaged DSR ranged between 117.5 W·m-2 and 245 W·m-2.Its strong radiation area is mainly concentrated over the northwest as well as the south of Yunnan Province,and the weak radiation area is mainly concentrated in the eastern part of Guizhou Province.The interannual variation shows a decreasing trend.The DSR variation in the Yunnan-Guizhou plateau has obvious seasonality.The overall spring radiation is the strongest and the winter radiation is the weakest.The maximum value of the overall monthly averaged DSR occurs in May,and the minimum value occurs in December over the YunnanKweichow Plateau.(2)The variation of DSR has an obvious periodicity over the Yunnan-Kweichow Plateau from 1984 to 2018.The time scale of the main cycle of monthly and seasonal averaged DSR is 18 months(6 seasons),of which the cycle of monthly averaged DSR is about 12 months and the cycle of seasonal averaged DSR is about 4 seasons.The first main cycle time scale for annual averaged DSR is 6 years with a period of about 3-5 years,and the second main cycle time scale is 13 years with a period of about 8-10 years.(3)The daily averaged DSR is unstable in terms of trend components and seasonal components in the Yunnan-Kweichow Plateau from 1984-2018.Based on the BFAST algorithm,the daily averaged DSR is detected to have breakpoints on the trend component and seasonal component.(4)The explanatory power of individual drivers for DSR in descending order is AOT(85.26%)> Longitude(84.48%)> Total Cloud Cover(76.36%)> Climate zones(51.99%)> Elevation(32.00%)> Precipitation(30.49%)> Latitude(29.14%)> Temperature(19.63%)> 10 m Wind Speed(15.96%)> Slope(0.74%)> Aspect(0.15%);The effects of the driving factors on DSR were not independent of each other and not simply superimposed.The interaction of the two factors on the DSR variation is significant,with the two-factor enhancement or non-linear enhancement;the risk detector shows that the DSR enhances with increasing aerosol optical thickness,latitude,and total cloud cover,and weakens with increasing elevation and longitude.