Drier soils get more afternoon rain than nearby wetter soils, according to an analysis of global satellite data presented in Nature this week.

These conclusions challenge most models, which suggest that wetter soils provide more favourable conditions for encouraging rainfall. Instead it is proposed that a greater flow of heat from drier soils encourages convection, a process involved in the development of storms.

Land surface properties, such as soil wetness, can affect atmospheric moisture content and are thought to influence rainfall patterns. However, in a global observational analysis, Christopher Taylor and colleagues reveal that rainfall occurrence is strongly favoured above dry soil rather than wet soil, especially in semi-arid climates. These results are consistent with enhanced afternoon convection occurring on drier soils, the authors explain. Their findings suggest that models may lack fundamental processes regulating convection and land–atmosphere interactions.