Fig. 2
From: Evolution of tropical cyclone genesis regions during the Cenozoic era
Differences in zonal mean genesis potential and environmental variables during storm season between the Early Eocene and pre-industrial. Over the western North Pacific (110–160°E): a Genesis potential index (GPI; number of events per month). b Potential intensity (PI; bars; m s−1), the enthalpy difference between sea surface and boundary layer (k*–k; red line; J kg−1), and the outflow temperature (OT; blue line; °C). c Vertical wind shear between 200 and 850 hPa (VS; bars; m s−1) and absolute meridional temperature gradient (MTG; red line; × 10‒6 °C m−1) in the troposphere. d Moist entropy deficit (X; bars), vertical temperature contrast (VTC; red line; °C) between surface and mid-troposphere (600 hPa), and relative humidity (RH; blue line; %) at 600hPa. e‒h same as a‒d but for the South Indian Ocean (40–100°E)
