Global dryland aridity changes indicated by atmospheric, hydrological, and vegetation observations at meteorological stations

Abstract. In the context of global warming, an increase in atmospheric aridity and global dryland expansion were expected under the future climate in previous studies. However, it conflicts with observed greening over drylands and the insignificant increase in hydrological and ecological aridity from the ecohydrology perspective. Combining climatic, hydrological, and vegetation data, this study evaluated global dryland aridity changes at meteorological sites from 2003 to 2019. A decoupling between atmospheric, hydrological, and vegetation aridity was found. Atmospheric aridity represented by the vapour pressure deficit (VPD) increased, hydrological aridity indicated by machine learning-based precipitation minus evapotranspiration (P-ET) data did not change significantly, and ecological aridity represented by leaf area index (LAI) decreased. P-ET showed non-significant changes in most of the dominant combinations of VPD, LAI, and P-ET. This study highlights the added values of using station scale data to assess dryland change as a complement to the results based on coarse resolution reanalysis data and land surface models.