scholarly journals Large Increasing Trend of Tropical Cyclone Rainfall in Taiwan and the Roles of Terrain

2013 ◽  
Vol 26 (12) ◽  
pp. 4138-4147 ◽  
Author(s):  
Chih-Pei Chang ◽  
Yi-Ting Yang ◽  
Hung-Chi Kuo
Keyword(s):  
Global Warming ◽  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Southwest Monsoon ◽  
Steering Flow ◽  
Terrain Effects ◽  
Typhoon Center ◽  
The Taiwan Strait ◽  
In The Beginning

Abstract Taiwan, which is in the middle of one of the most active of the western North Pacific Ocean’s tropical cyclone (TC) zones, experienced a dramatic increase in typhoon-related rainfall in the beginning of the twenty-first century. This record-breaking increase has led to suggestions that it is the manifestation of the effects of global warming. With rainfall significantly influenced by its steep terrain, Taiwan offers a natural laboratory to study the role that terrain effects may play in the climate change of TC rainfall. Here, it is shown that most of the recently observed large increases in typhoon-related rainfall are the result of slow-moving TCs and the location of their tracks relative to the meso-α-scale terrain. In addition, stronger interaction between the typhoon circulation and southwest monsoon wind surges after the typhoon center moves into the Taiwan Strait may cause a long-term trend of increasing typhoon rainfall intensity, which is not observed before the typhoon center exits Taiwan. The variation in the location of the track cannot be related to the effects of global warming on western North Pacific TC tracks reported in the literature. The weaker steering flow and the stronger monsoon–TC interaction are consistent with the recently discovered multidecadal trend of intensifying subtropical monsoon and tropical circulations, which is contrary to some theoretical and model projections of global warming. There is also no evidence of a positive feedback between global warming–related water vapor supply and TC intensity, as the number of strong landfalling TCs has decreased significantly since 1960 and the recent heavy rainfall typhoons are all of weak-to-medium intensity.

Future Changes in the Tropical Cyclone Intensity and Frequency over the Western North Pacific Based on 20-km HiRAM and MRI Models

2020 ◽  
pp. 1-47
Author(s):  
Chi-Cherng Hong ◽  
Chih-Hua Tsou ◽  
Pang-Chi Hsu ◽  
Kuan-Chieh Chen ◽  
Hsin-Chien Liang ◽  
...  
Keyword(s):  
Global Warming ◽  
Tropical Cyclone ◽  
Energy Conversion ◽  
North Pacific ◽  
Western North Pacific ◽  
Synoptic Scale ◽  
Steering Flow ◽  
The Future ◽  
Budget Equation ◽  
Upper Level

AbstractThe future changes in the tropical cyclone (TC) intensity and frequency over the western North Pacific (WNP) under global warming remain uncertain. In this study, we investigated such changes using 20-km resolution HiRAM and MRI models, which can realistically simulate the TC activity in the present climate. We found that the mean intensity of TCs in the future (2075−2099) would increase by approximately 15%, along with an eastward shift of TC genesis location in response to the El-Niño like warming. However, the lifetime of future TCs would be shortened because the TCs tend to have more poleward genesis locations and move faster due to a stronger steering flow related to the strengthened WNP subtropical high in a warmer climate. In other words, the enhancement of TC intensity in future is not attributable to the duration of TC lifetime.To understand the processes responsible for the change in TC intensity in a warmer climate, we applied the budget equation of synoptic-scale eddy kinetic energy along the TC tracks in model simulations. The diagnostic results suggested that both the upper level baroclinic energy conversion (CE) and lower-level barotropical energy conversion (CK) contribute to the intensified TCs under global warming. The increased CE results from the enhancement of TC-related perturbations of temperature and vertical velocity over the subtropical WNP, whereas the increased CK mainly comes from synoptic-scale eddies interacting with enhanced zonal-wind convergence associated with seasonal mean and intraseasonal flows over Southeast China and the northwestern sector of WNP.

scholarly journals Interannual and interdecadal impact of Western North Pacific Subtropical High on tropical cyclone activity

2020 ◽  
Vol 54 (3-4) ◽  
pp. 2237-2248 ◽  
Author(s):  
Qiong Wu ◽  
Xiaochun Wang ◽  
Li Tao
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Southern Oscillation ◽  
Subtropical High ◽  
Interdecadal Change ◽  
Steering Flow ◽  
The Pacific ◽  
Sea Surface Temperature Anomalies ◽  
Peak Phase

AbstractIn this study, we analyzed the impacts of Western North Pacific Subtropical High (WNPSH) on tropical cyclone (TC) activity on both interannual and interdecadal timescales. Based on a clustering analysis method, we grouped TCs in the Western North Pacific into three clusters according to their track patterns. We mainly focus on Cluster 1 (C1) TCs in this work, which is characterized by forming north of 15° N and moving northward. On interannual timescale, the number of C1 TCs is influenced by the intensity variability of the WNPSH, which is represented by the first Empirical Orthogonal Function (EOF) of 850 hPa geopotential height of the region. The WNPSH itself is modulated by the El Niño–Southern Oscillation at its peak phase in the previous winter, as well as Indian and Atlantic Ocean sea surface temperature anomalies in following seasons. The second EOF mode shows the interdecadal change of WNPSH intensity. The interdecadal variability of WNPSH intensity related to the Pacific climate regime shift could cause anomalies of the steering flow, and lead to the longitudinal shift of C1 TC track. Negative phases of interdecadal Pacific oscillation are associated with easterly anomaly of steering flow, westward shift of C1 TC track, and large TC impact on the East Asia coastal area.

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