Fig. 2: Strong causality of sub-processes by which boreal warm-season surface soil moisture (SSM) affects precipitation (P) based on ERA5 reanalysis.
From: Causal pathways underlying global soil moisture–precipitation coupling
a Land area fractions (LAFs; %) of significant SSM→evapotranspiration (ET), SSM→sensible heat (SH), ET→P and SH→P causality (p < 0.1) over the global land. b Global map of the pathways underlying SSM–P coupling. The SSM→ET→P pathway occurs over the overlapping areas with significant SSM→ET and ET→P causality, the SSM→SH→P pathway occurs over the overlapping areas with significant SSM→SH and SH→P causality, and thus over the overlapping areas with significant causality of all four sub-processes, both pathways occur. The royal blue lines denote the 2500-m isoline of terrain height. c Atmospheric moisture flux convergence (MFC) regime (mm day−1) and proportions (%) of grid cells with significant SSM→ET, ET→lifting condensation level (LCL) and ET→P causality over the eight SSM–P coupling hotspots. d Same as (c), but for boundary layer height (BLH) variability (−) and proportions of grid cells with significant SSM→SH, SH→BLH and SH→P causality. Here, BLH variability is defined as the ratio of BLH standard deviation to its climatological mean.
