Sideswiping Tropical Cyclones and Their Associated Precipitation over China

Abstract

Tropical cyclone (TC) precipitation (TCP) has attracted considerable attention in recent decades because of its adverse socioeconomic impacts. In particular, considerable effort has been devoted to quantifying TCP and investigating the precipitation of TCs that make landfall. However, precipitation over land induced by TCs that do not make landfall (i.e., offshore), the so-called “sideswiping” TCs (STCs), is an important component of TCP but has attracted little attention from the research community to date. Here, best-track and daily precipitation data from the China Meteorological Administration during the 59 years of 1960–2018 are used to study STC precipitation (STP). Results show that: (i) the annual number of STCs fluctuates significantly from 3 to 17, with a mean frequency of 8.8 STCs per year; (ii) there are decreasing trends in STC frequency and STP amount over the past 59 years; (iii) both STC frequency and STP are high from July to October, with maxima in August; (iv) the distribution of STP, covering most of China’s coastal regions, is dominated by intense STCs, and the annual STP decreases from southeast coastal regions to northwest inland areas, with a maximum value over the islands of Taiwan and Hainan; and (v) extreme STP events could appear not only over the island and coastal areas, but also over inland areas such as Zhumadian of Henan Province due to the influences of local orography and favorable large-scale forcing.

摘 要

热带气旋(TC)降水(TCP)由于其不利的社会经济影响, 在近几十年引起了广泛关注, 特别是在TCP和登陆TC降水方面的研究. 然而, 由未登陆TC (即近海TC), 也是所谓的 “擦边” TC (STC) 造成的陆上降水, 是 TCP 的重要组成部分, 却很少受到研究关注. 本文采用中国气象局 1960–2108 年 59 年间的 TC 最佳路径资料和日降水资料来研究擦边 TC 降水 (STP), 结果表明: (1) STC 年频数波动较大, 从 3 个到 17 个不等, 平均每年 8.8 个; (2) 从年际变化来看, STC 年频数和 STP 年总量在过去 59 年里均呈下降趋势; (3) STC 频数和 STP 的月际分布均呈单峰型, 在 7–10 月较高, 峰值为 8 月; (4) STP 空间分布覆盖中国大部分沿海地区, 且主要由强 TC 决定, 年平均 STP 从东南沿海地区到西北内陆逐渐下降, 最大值出现在台湾和海南; (5) 由于局部地形和有利的大尺度强迫作用, 极端 STP 事件不仅可能出现在海岛和沿海地区, 也可能出现在河南省驻马店等内陆地区.