A study on the structural evolution of Typhoon Kong-Rey (2013) and its relationship with convective precipitation

• Main Authors: Li, Mao-Cheng, 李茂正
• Other Authors: Wang, Chung-Chieh
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/56370234829019655379

碩士 === 國立臺灣師範大學 === 地球科學系 === 104 === Tropical Storm (TS) Kong-Rey (2013) affected Taiwan in late August 2013. During this period, satellite and radar observations indicated clear asymmetric structure, with its active convection and rainfall located most to the south and southwest of the typhoon center and a tilted vortex vertical structure. As a result, the maximum rainfall in Taiwan was over its southwestern region and far from the typhoon center, with an accumulative amount of over 500-700 mm that caused much damage and several casualties. On the other hand, over northern and eastern Taiwan closer to the storm center, only little rainfall was received (mostly below 50 mm). In this study, the Cloud-Resolving Storm Simulator (CReSS) is used to successfully reproduce the evolution of TS Kong-Rey and related whether phenomena during the period when it affected Taiwan. The control (CTRL) simulation shows that the asymmetric rainfall of the storm was mainly due to the strong vertical wind shear (from northeast to southwest) in the environmental flow during the approach of Kong-Rey over the Bashi Channel. An intense rainband formed along the convergence zone between the northerly typhoon circulation and the southwesterly flow over the southern Taiwan Strait. Later when the storm moved further north, this rainband also moved overland into southwestern Taiwan and became stationary and north-south oriented (parallel to topography), and produced heavy rainfall and the subsequent hazards with enhancement from terrain uplifting. In the CTRL experiment, the convection is also phase-locked to the topography of Taiwan, and the associated latent heating effect leads to an increase in mid-level potential vorticity (PV) with time and a westward moving tendency of the mid-level vortex. In contrast, the low-level storm center, being blocked by the Central Mountain Range (CMR), continues to move northward as observed and results in the significant vertical tilt (toward the Taiwan terrain with height). In the “no-terrain” (NT) where the Taiwan topography is removed, the strong convection and rainband become migratory and move with the storm, more rain is simulated over northern and eastern Taiwan, the PV production over Taiwan is less, and the vertical tilt of the storm is also reduced compared to the CTRL. Thus, the topographic effect of Taiwan on convection and precipitation was also a key factor (in addition to the vertical wind shear) in the maintenance of the tilted vertical structure of Kong-Rey (2013) when it passed by Taiwan.