Sensitivity of the Intensity and Structure of Tropical Cyclones to Tropospheric Stability Conditions

Tetsuya Takemi,Shota Yamasaki

doi:10.3390/atmos11040411

Abstract

The intensity of tropical cyclones (TCs) is controlled by their environmental conditions. In addition to the sea surface temperature, tropospheric temperature lapse rate and tropopause height are highly variable. This study investigates the sensitivity of the intensity and structure of TCs to environmental static stability with a fixed sea surface temperature by conducting a large ensemble of axisymmetric numerical experiments in which tropopause height and tropospheric temperature lapse rate are systematically changed based on the observed environmental properties for TCs that occurred in the western North Pacific. The results indicate that the intensity of the simulated TCs changes more sharply with the increase in the temperature lapse rate than with the increase in the tropopause height. The increases in the intensity of TCs are 1.3–1.9 m s−1 per 1% change of the lapse rate and 0.1–0.5 m s−1 per 1% change of the tropopause height. With the increase in the intensity of TCs, supergradient wind at low levels and double warm core structures are evident. Specifically, the formation of the warm core at the lower levels is closely tied with the intensification of TCs, and the temperature excess of the lower warm core becomes larger in higher lapse rate cases.

Highlights

The development of tropical cyclones (TCs) is controlled by their environmental conditions.Diagnosing and predicting the maximum intensity achievable during the lifetime of TCs are important to forecasting severe weather and hazards due to TCs
Emanuel [2,3] put forth a maximum potential intensity (MPI) theory based on the proposition that TC circulation can be regarded as a Carnot heat cycle
The purpose of this study is to quantify the impacts of environmental static stability on the intensity and structure of TCs by conducting a large number of numerical experiments with the use of an axisymmetric, non-hydrostatic model configured in environments with stability conditions systematically changed

Summary

Introduction

Diagnosing and predicting the maximum intensity achievable during the lifetime of TCs are important to forecasting severe weather and hazards due to TCs. Gray [1] statistically identified environmental conditions favorable for the development of TCs, and indicated that TCs favorably develop under conditions with warm SST, convective instability in the lower troposphere, positive relative vorticity at low-levels, weak vertical wind shear, high relative humidity at middle-levels, and significant planetary vorticity. Bister and Emanuel [9] updated the MPI equation to show that the surface enthalpy flux term can be replaced with convective available potential energy (CAPE) In this way, the atmospheric stability conditions play a role in determining the intensity of TCs

Objectives

Results

Conclusion