On the factors affecting trends and variability in tropical cyclone potential intensity

Abstract

Tropical cyclone potential intensity (V[subscript p]) is controlled by thermodynamic air-sea disequilibrium and thermodynamic efficiency, which is a function of the sea surface temperature and the tropical cyclone’s outflow temperature. Observed trends and variability in V[subscript p] in each ocean basin are decomposed into contributions from these two components. Robustly detectable trends are found only in the North Atlantic, where tropical tropopause layer (TTL) cooling contributes up to a third of the increase in Vp. The contribution from disequilibrium dominates the few statistically significant V[subscript p] trends in the other basins. The results are sensitive to the data set used and details of the V[subscript p] calculation, reflecting uncertainties in TTL temperature trends and the difficulty of estimating V[subscript p] and its components. We also find that 20–71% of the interannual variability in V[subscript p] is linked to the TTL, with correlations between detrended time series of thermodynamic efficiency and V[subscript p] occurring over all ocean basins.