Hydroclimate Correlations Between the Alxa Desert and Adjacent Mountains in Northwestern China: Evidence From Meteorological and Tree-Ring Data

It is important to understand the hydroclimate history of water-deficient regions, such as the Alxa desert of northwest China. However, there are few high-resolution proxy records for the hydroclimate changes over the past centuries in the Alxa desert. Fortunately, there are many tree-ring hydroclimate reconstructions from the nearby mountains. However, the hydroclimate correlations between the Alxa desert and adjacent mountains are unclear. Here, we collected high-quality data from 43 meteorological stations in northwest China (1960-2017). We found increasing mean temperatures in the study area, both on seasonal and annual timescales. We also found that while relative humidity had mostly decreased in the Mt. Qilian and Alxa desert, precipitation and the standardized precipitation evapotranspiration index (SPEI) increased mostly. In the Mt. Helan and Hasi ranges, relative humidity, precipitation, and SPEI all showed decreasing trends. Empirical orthogonal function analysis indicated that precipitation, relative humidity, and SPEI in the Mt. Qilian were similar to the corresponding conditions in the central and western Alxa desert. Hydroclimate conditions in the Mt. Helan and Hasi ranges were correlated with data from the eastern desert. Tree-ring records of precipitation and SPEI from the mountains were used to validate the hydroclimate correlations during the instrumental period. We found strong similarities between hydroclimatic changes in the Mt. Qilian and those in the central and western Alxa desert, on both annual and decadal timescales, from 1877 to 2006. Tree-ring width chronologies from mountainous areas were shown to faithfully represent the hydroclimatic history of the desert area.