The Effect of Initial Vortex Asymmetric Structure on Tropical Cyclone Intensity Change in Response to an Imposed Environmental Vertical Wind Shear

Abstract

Previous studies have investigated how the environmental vertical wind shear (VWS) may trigger the asymmetric structure in an initially axisymmetric tropical cyclone (TC) vortex and how TC intensity changes in response. In this study, the possible effect of the initial vortex asymmetric structure on the TC intensity change in response to an imposed environmental VWS is investigated based on idealized full‐physics model simulations. Results show that the effect of the asymmetric structure in the initial TC vortex can either enhance or suppress the initial weakening of the TC in response to the imposed environmental VWS. When the initial asymmetric structure is in phase of the VWS‐induced asymmetric structure, the TC weakening will be enhanced and vice versa. Our finding calls for realistic representation of initial TC asymmetric structure in numerical weather prediction models and observations to better resolve the asymmetric structure in TCs.

Dependence of Tropical Cyclone Weakening Rate in Response to an Imposed Moderate Environmental Vertical Wind Shear on the Warm‐Core Strength and Height of the Initial Vortex

“…All simulation data that support the findings of this study are publicly available from Gao and Wang (2024).…”

“…The vertical profile of the environmental zonal winds is showed in Figure 1a (inset vignette). Only results from four VWS experiments with an initially axisymmetric TC vortex in Gao and Wang (2023) are used in this study. Namely, in these experiments, the moderate environmental VWS was imposed onto an initially axisymmetric vortex after 24 (SHE24_AXI), 48 (SHE48_AXI), 72 (SHE72_AXI), and 96 hr (SHE96_AXI) of the simulation during the TC intensifying period in a quiescent environment experiment (CTRL), respectively.…”

“…In a recent study, Gao and Wang (2023) found a strong dependence of TC weakening in response to an imposed moderate VWS on the stage of an intensifying TC. Since the different stages of the intensifying TC correspond to different warm‐core strengths and heights of the TC, they hypothesized that the TC intensity change rate in response to an imposed moderate VWS might depend on the warm‐core strength and height of the initial TC vortex, which was defined as the maximum potential temperature ( θ ) anomaly over the TC center relative to the TC environment (Xi et al., 2021).…”

“…The environmental θ at a certain level was defined as the mean θ of the outermost grids in four directions in the outermost domain. Because Gao and Wang (2023) focused on how the asymmetric structure of the initial TC vortex affects the TC intensity change in response to an imposed moderate VWS, they did not examine the detailed physical processes. This study can be considered as an extension of Gao and Wang (2023) with the focus on the dependence of the initial weakening rate of an intensifying TC on the warm‐core strength and height in response to an imposed moderate VWS on an f ‐plane using idealized numerical experiments performed in Gao and Wang (2023).…”

Added Value of Three‐Dimensional Horizontal Winds From Geostationary Interferometric Infrared Sounder for Typhoon Forecast in a Regional NWP Model

“…Although assimilating remote sensing measurements related to thermodynamic (Wang et al., 2015, 2019) and hydrometeor (Meng, Wang, et al., 2021, 2022) into NWP models can enhance the asymmetric component, which is highly correlated with the development of TC intensity (Gao & Wang, 2023; Kurihara et al., 1993), this study marks the first effort to synergistically assimilate the 3D horizontal wind from GeoHIS and Liquid Water Path (LWP) and Ice Water Path (IWP) derived from geostationary satellite imager. It is known that even if hydrometeor information is accurately analyzed in the initial conditions, it is hard for the model to retain this information for long without appropriate dynamical support.…”