The Sensitivity of Tropical Cyclone Potential Intensity to Atmospheric Temperature Perturbations

The maximum potential intensity (PI) of tropical cyclones is affected by changes in the air-sea thermodynamic disequilibrium and factors controlling the outflow temperature. Changes in PI are of interest for interpreting observed changes in tropical cyclone activity and projections of future changes. Here, the sensitivity of PI to infinitesimal perturbations in the temperature of the free troposphere is assessed. In reanalysis estimates, the vertical structure of the PI sensitivity peaks near 100 hPa where a 1 K warming leads to a decrease of PI by about 0.3 m/s and exhibits much reduced sensitivity to mid-troposphere temperature changes. The sensitivity of PI varies between ocean basins with greater sensitivity in the northeast Pacific and Atlantic than the West Pacific. The PI sensitivity, therefore, reveals that spatial variations in climatological stratification and humidity can lead to differential PI changes even with horizontally homogeneous atmospheric warming in the tropical free troposphere.