Evolution of the upper-level thermal structure in tropical cyclones

Abstract

Tropical cyclones (TCs) are associated with tropopause-level cooling above tropospheric warming. We collect temperature retrievals from 2007 to 2014 near worldwide hurricane-strength TCs using three remote sensing platforms: the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), the Advanced Microwave Sounding Unit-A (AMSU-A), and geostationary infrared (IR) imagery. These retrievals are composited about the lifetime maximum intensity (LMI) to examine the evolution of the fine-scale temperature structure within TCs. The convective structure evolves highly asymmetrically about LMI, while intensity evolution shows a much weaker degree of asymmetry. Relative to the far-field structure, tropopause-level cooling occurs before a tropospheric warm core is established. We speculate that the associated convective destabilization exerts a positive feedback on TC development by increasing the depth of existing convection. Tropopause-level cold anomalies move away from the storm after LMI, potentially increasing the near-surface horizontal pressure gradient toward the storm center and increasing the maximum winds.