Observed Shear-Relative Rainfall Asymmetries Associated with Landfalling Tropical Cyclones

Xiang Wang,Haiyan Jiang,Xun Li,Jun A Zhang

doi:10.1155/2021/4676713

Abstract

This study examines the shear-relative rainfall spatial distribution of tropical cyclones (TCs) during landfall based on the 19-year (1998–2016) TRMM satellite 3B42 rainfall estimate dataset and investigates the role of upper-tropospheric troughs on the rainfall intensity and distribution after TCs make a landfall over the six basins of Atlantic (ATL), eastern and central Pacific (EPA), northwestern Pacific (NWP), northern Indian Ocean (NIO), southern Indian Ocean (SIO), and South Pacific (SPA). The results show that the wavenumber 1 perturbation can contribute ∼ 50% of the total perturbation energy of total TC rainfall. Wavenumber 1 rainfall asymmetry presents the downshear-left maxima in the deep-layer vertical wind shear between 200 and 850 hPa for all the six basins prior to making a landfall. In general, wavenumber 1 rainfall tends to decrease less if there is an interaction between TCs and upper-level troughs located at the upstream of TCs over land. The maximum TC rain rate distributions tend to be located at the downshear-left (downshear) quadrant under the high (low)-potential vorticity conditions.

Highlights

Landfalling tropical cyclones (TCs) can bring strong winds and heavy precipitation, which cause tremendous damage to the affected region [1]
Before comparing the rainfall asymmetry usually represented by the decomposed field of wavenumber 1, we examined how the azimuthal mean rain rates distribute radially among different basins to understand the relative amplitude of the composited field to the mean rain rate for different TC subregions
Is result is similar to the recent satellite composites by Ankur et al [10]. e peak azimuthal mean rain rates for six basins experience a slight enhancement during the course of TCs approaching the coast and making landfall with the rain rate of ∼ 5.0–5.8 mm·hr−1 (Figure 1(b)). is can be explained by the fact that the surface frictional convergence between the land and ocean in landfalling TCs [32, 42] is consistent with previous studies [27, 30, 61, 62]

Summary

Introduction

Landfalling tropical cyclones (TCs) can bring strong winds and heavy precipitation, which cause tremendous damage to the affected region [1]. Flash flooding and landslides associated with long-duration rainfall of landfalling TCs have been the predominant causes of death all over the world [2]. E devastated regions are largely determined by the distribution of rainfall in landfalling TCs [3]. Earlier studies revealed that the mean rain rate in the TC eyewall increased as the storm intensified by using airborne radar datasets. Marks [6] showed that Hurricane Allen (1980) exhibited an azimuthal mean rain rate greater than mm h−1 in the eyewall, which was six times more than that within a radius of 111 km of mature Allen’s center. Burpee and Black [7] found that the eyewall of Hurricane Alicia (1983) became circular as the maximum low-level winds approached 50 m s−1, while a second eyewall had shaped outside the original eyewall when the minimum central surface pressure dropped to 970 hPa

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Results

Conclusion