Stronger Warming Amplification over Arid Ecoregions and Its Relationship to Vegetation Cover in China since 1982

To analyze vegetation variability and its relationship with summer air temperature variability in China, this study classifies various ecoregions based on the climatological Normalized Difference Vegetation Index (NDVI) values. Results show that there is a decreasing spatial distribution of vegetation from east to west in China. Arid ecoregions are the most obvious areas for summer warming since 1982. The warming rates over arid ecoregions for summer mean air temperature and mean maximum air temperature are 0.6-1.0℃/10 a and that for summer mean minimum air temperature is 0.8-1.4℃/10 a. Furthermore, summer air temperature variations have a significant negative correlation with vegetation conditions since 1982. In other words, the lower the vegetation greenness is, the stronger the warming trend is. It is worth noting that the negative correlation is most significant between mean minimum air temperature and vegetation conditions. In each ecoregion, the long-term trend of temperature is largely affected by changes in albedo and clouds. In the sparse vegetation regions, the increased albedo leads to a decrease in latent heat transport and increases the sensible heat flux, which intensifies the warming trend. In the dense vegetation regions, the decline in albedo leads to increases in evaporative cooling, which slows the rate of increase in the air temperature. Overall, vegetation activities play an important role in regional climate change, especially over the arid regions, where significant changes in surface radiation balance and energy flux amplify the rate of warming.