Fig. 2: The moisture transport and associated lower-level atmospheric circulations in August.

a The topographic height (m; shading) and horizontal wind at 850 hPa of climatology (m s^–1; vector). b The column-integrated moisture flux (from surface to 300 hPa; kg m^–1 s^–1; vector) and precipitation (mm day^–1; shading) of climatology. The numbers denote net water vapor input (positive) or output (negative) (Kg s^–1) across four boundaries of the key region. c The anomalies of horizontal wind at 850 hPa (m s^–1; vector) and surface pressure (hPa; shading) in 2022, with the dashed box outlines the region for defining the easterly index (EI). d The anomalies of column-integrated moisture flux (kg m^–1 s^–1; vector) and its divergence (×10^–5 kg m^–2 s^–1; shading) in 2022. The black and red numbers/thick arrow denote net water vapor input (or output) in 2022 and their departure from the climatology, respectively. e The standardized time series of SPRI (black) and EI (red) from 1979 to 2022. f Same as in (d), but for the regressions against the standardized EI during 1979–2022, in which black dots denote significance at p = 0.05 level.