Dependence of tropical cyclone intensification rate on sea‐surface temperature (original) (raw)

The dependence of tropical cyclone intensification rate on the sea-surface temperature (SST) is examined in the prototype problem for tropical cyclone intensification on an fplane using a three-dimensional, non-hydrostatic numerical model. The effects of changing the SST are compared with those of changing the latitude examined in a recent article. It is found that the dependence of intensification rate on latitude is largest when the SST is marginal for tropical cyclone intensification (26 • C) and reduces in significance as the SST is increased. Further, at a given latitude, intensification begins earlier and the rate of intensification increases with increasing SST, on account of a significant increase of surface moisture fluxes from the warmer ocean. These higher fluxes result in higher values of near-surface moisture and equivalent potential temperature, leading to a larger radial gradient of diabatic heating rate in the low to middle troposphere above the boundary layer. This larger radial gradient leads to a stronger overturning circulation, which in turn leads to a stronger radial import of absolute angular momentum surfaces and therefore more rapid spin-up. These arguments invoke the classical axisymmetric spin-up mechanism. Non-axisymmetric issues are touched upon briefly.