Fig. 5: Large-scale atmospheric circulation and climatic drivers associated with tropical transboundary warm-season heatwaves.

a Maps show the temperature composite anomalies (red shading) and 850-hPa horizontal winds (vector) for the two days before, the day of, and the two days after landfalling for all ocean-to-land heatwave (OTLH) events from the Pacific to eastern Asia based on ERA5 during 1981–2020. The red contour presents the spatial range of the western North Pacific Subtropical High, characterized by 5880 m geopotential height. b The same as (a), but for the two days before, the day of, and the two days after offshore for all land-to-ocean heatwaves (LTOHs) from western Australia to the Pacific. The black contour shows that 500-hPa geopotential height anomalies (unit: gpm) compared to non-heatwave conditions during 1981–2020. c Map shows the differences in zonal wind (shading) and horizontal wind (arrows) during the lifetime of OTLHs between the period of 2001–2020 and 1981–2000 based on ERA5. d Map shows the zonal temperature difference on the hottest 10% of days at each grid cell during 2001–2020 compared to those during 1981–2000 based on ERA5. Dots indicate the temperature difference at grid cells is more than 1.5 times (or less than – 1.5 times) the standard deviation of all grid cells in the same zonal region.