The Effect Of Vegetation Cover Change On Regional Climate Effect Of Dust Over Northern China Based On RegCM

The spatiotemporal changes of sand and dust events are affected by global climate change and human activities,which have a significant impact on the regional climate.This study used AVHRR VCF data,combined with satellite-based terrain data,and GIMMS NDVI data products to build a BATS-based annual land cover data(AVHRR-BATS).At the same time,based on land use status database of remote sensing monitoring in China and its classification system,with ERA-interim global atmospheric reanalysis data as climate forcing data,the availability of the AVHRR-BATS land cover data and the data in the simulation of sand and dust events based on BATS land surface model were verified.Through the comparison of spring scenarios during 2000?2015,the impact of surface cover changes on sand and dust events in northern China and its climatic effects were simulated.The effects of sand and dust on temperature and precipitation under the background of vegetation change and climate change were explained by the spatiotemporal changes of sand dust aerosol radiative forcing and circulation.The main research conclusions are:(1)The Reg CM-DUST coupling model can better simulate the spatiotemporal distribution of sand and dust events,and the process of sand and dust discharge and transportation in northern China.Although the Reg CM-DUST coupling model and MERRA2 have significant differences in the sand and dust simulation,their DAOD based on 2 land surface models and 4 underlying surface data simulations all show good consistency with MERRA2 DAOD.The interannual change trends of the two are roughly the same,with an average correlation coefficient of 0.769 and an average offset of 0.083.Among them,the sand and dust event simulated by the AVHRR VCF data decision tree classification results as the input of the BATS land surface model is superior to the other three scenarios in terms of spatial and temporal distribution.The RMSE in the spatial distribution is 0.062,and the offset in the temporal distribution is 0.058±0.050.The results show that the sand and dust events simulated under the land surface model and underlying surface data are more suitable for studying the impact of vegetation changes on sand and dust events in northern China.(2)The BATS classification standard based on land use data by decision tree classification with AVHRR VCF data is more accurate in the desert and semi-desert distribution in northern China.Its accuracy meets or surpasses the ESA CCI-LC data level.At the same time,it can better represent the actual land use time changes.AVHRR VCF data is suitable for land surface data input of Reg CM model sand and dust events simulation.(3)Vegetation changes not only have a significant impact on sand and dust events but also have an impact on the climate effects of sand and dust.At the time and space scales,the change of sand and dust indicators caused by vegetation changes significantly affects its climatic effects on radiative forcing,temperature,circulation,and precipitation.With the spread of sand and dust,it affects a large area of sand and dust in northern China.Dust aerosols have a cooling effect on the temperature in most parts of northern China from spring during 2000?2015(0.28°C for average).For the main sand source area,the increase of vegetation makes its surface albedo decrease.The increase in evapotranspiration leads to the transfer of latent heat flux between the surface and the atmosphere,which in turn enhances the cooling effect of sand and dust on the ground-gas system.The cooling effect is more obvious in the area with larger surface radiative forcing.The accumulation of atmospheric dust in the main sand source area absorbs a large amount of solar radiation and causes an increase in temperature.In general,sand and dust contribute to the increase of precipitation in northern China during the spring of 2000?2015(0.005×10^-6kg/m²·day for average).Under the influence of vegetation,although the sand and dust in the sand and dust affected area still mainly reduce the precipitation by enhancing the circulation,the improvement of the vegetation is beneficial to the reduction of the sand and dust,which in turn weakens the control of the circulation and increases the precipitation.In addition,the seasonal changes weaken the impact of dust on the circulation.