Changes in the hydrological properties of inner East Asia during the boreal summer and possible mechanisms

We investigated changes in the hydrological cycle in inner East Asia during the boreal summer (June-to-August) from 1979 to 2020 by analyzing climate variables including latent heat flux, precipitation and soil moisture. We found that the correlation between latent heat flux (LH) and precipitation varies across East Asia, with a negative correlation dominating over the summer monsoon region. In contrast, LH is positively correlated with precipitation in inner East Asia. Additional analyses indicate a positive correlation of LH-precipitation, implying a coupling of land and atmosphere that becomes strong in inner East Asia across the late 1990s. Soil moisture is also consistently and significantly reduced in inner East Asia after the late 1990s, which could be associated with the strengthening of a positive correlation of LH-precipitation. A tripole-like sea surface temperature (SST) in the North Atlantic Ocean causes anomalous anticyclonic circulation in inner East Asia through zonal wave propagation, resulting in a significant reduction of soil moisture. Our results indicate that the hydrological cycle in inner East Asia is influenced remotely by North Atlantic SST through soil moisture – precipitation feedback.