Examining asymmetric outer-core CAPE in sheared tropical cyclones based on the FNL data set

Abstract

The asymmetric distribution of convective available potential energy (CAPE) in the outer core of sheared tropical cyclones (TCs) is examined using the National Centers for Environmental Prediction Final operational global analysis data. Larger (smaller) CAPE tends to appear in the downshear (upshear) semicircle. This downshear-upshear contrast in CAPE magnitude becomes much more statistically significant in moderate-to-strong shear. The azimuthally asymmetric CAPE is closely associated with the near-surface equivalent potential temperature ({\theta }_e). Larger surface winds occur in the upshear semicircle in strongly sheared TCs, contributing to larger surface latent heat fluxes in those quadrants. More low-level air well fueled by the larger surface latent heat fluxes in the upshear quadrants is cyclonically advected into the downstream quadrants. As a result, larger near-surface {\theta }_e and CAPE are found in the outer core in the downshear quadrants.

Graphical abstract

Keywords

tropical cyclone / outer core / asymmetry / CAPE / reanalysis dataset

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Acknowledgments

This work was jointly supported by the National Key Research and Development Program of China (No. 2017YFC1501601), the National Natural Science Foundation of China (Grant Nos. 41475058, 41730961, 41675044, 41730960, and 41875054), and the Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province Foundation (No. SCSF202003).

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