Fig. 2: Characteristics of observed and model-simulated tropical convection.

a Joint probability density distribution of observed vertical velocity at 500 hPa and precipitation over the tropical ocean at each grid point from 1979 to 2022. Markers indicate the precipitation intensity corresponding to zero vertical velocity over the observation period (1979–2022, 1979–1994, 1995–2008, 2009–2022) with regression lines. b Relationship between the tropical mean SST from HadISST and the tropical mean 300 hPa temperature in ERA5. Shading indicates the corresponding SST threshold for convection based on HadISST with GPCP v2.3 from 1979 to 2022, while purple markers without shading indicate from 1950 to 1978. A solid line indicates the regression line for 73 years. c CESM simulated joint probability density distribution of vertical velocity at 500 hPa and precipitation over the tropical ocean at each grid point during the present day. The markers and lines represent the same things as in (a). Blue colors indicate the value of the ramp-down period (2070) and red colors indicate the value of the ramp-up period (2210). d Relationship between the tropical mean SST and the tropical mean 300 hPa temperature in CESM during the ramp-up and ramp-down. Markers indicate the ensemble-averaged 31-year value of the ramp-down period (red) and the ramp-down period (blue). A colored legend indicates the corresponding SST threshold for convection. The correlation coefficient (corre. coeff.) and slope of both periods are also provided.