The Effects of Topography on the Evolution of Typhoon Saomai (2006) under the Influence of Tropical Storm Bopha (2006)

Abstract

The effects of topography on the evolution of Typhoon Saomai (2006) are investigated by conducting a series of numerical simulations with the Weather Research and Forecasting (WRF) Model using 100%, 75%, 50%, and 25% of terrain heights of the Central Mountain Range (CMR) in Taiwan. Differences in the track and intensity of Typhoon Saomai between the experiments are strongly related to those of Tropical Storm Bopha, which passed Taiwan earlier than the typhoon. In the sensitivity experiments, the higher CMR drifts Bopha more southward, which results in the weakening of Bopha by prohibiting the interaction between the CMR and Bopha, and the flows induced by Bopha force Saomai to propagate along a more southerly track. The higher CMR weakens the easterly flow in the lower troposphere and suppresses the northerly flow in the upper troposphere to the west of Saomai. The resultant weak vertical wind shear keeps warm air near the typhoon center in the upper troposphere, which promotes the intensification of the typhoon. To examine the direct effects of topography on the track and intensity of Saomai, additional simulations involving the removal of Bopha from the initial condition with 100% and 50% of CMR are conducted. The results without Bopha showed that Saomai moves more southward at a slower speed and with greater intensity, due to the stronger northerly wind to the west of Saomai, which was not canceled out by the southerly wind to the east of Bopha, and there is no significant difference in the tracks or intensity with respect to the mountain heights.

Investigating the Mechanisms Associated With the Evolutions of Twin Extratropical Cyclones Over the Northwest Pacific Ocean in Mid‐January 2011

“…The focus of this study is therefore the investigation of interactions between the twin cyclones, the mechanisms dominating their significantly different transitions, and the factors and associated mechanisms for inducing the extreme EEC. This effect can be a source of errors in the forecast of cyclone track, intensity, and structure (Brand, 1970;Jang & Chun, 2013;Liu & Tan, 2016;Ziv & Alpert, 1995). They have the potential to experience the "Fujiwhara effect" (Fujiwhara, 1923), where cyclones in relatively close proximity rotate cyclonically around each other and in some instances amalgamating into a single cyclone (Dong & Neumann, 1983;Hoover, 1961;Prieto et al, 2003).…”

“…They have the potential to experience the "Fujiwhara effect" (Fujiwhara, 1923), where cyclones in relatively close proximity rotate cyclonically around each other and in some instances amalgamating into a single cyclone (Dong & Neumann, 1983;Hoover, 1961;Prieto et al, 2003). This effect can be a source of errors in the forecast of cyclone track, intensity, and structure (Brand, 1970;Jang & Chun, 2013;Liu & Tan, 2016;Ziv & Alpert, 1995).…”

Horizontal divergence of typhoon-generated gravity waves in the upper troposphere and lower stratosphere (UTLS) and its influence on typhoon evolution

“…1c) is generally well matched during 12 h of period of Typhoon intensification (00:00 UTC, 9 August to 12:00 UTC, 9 August), while they are less correlated in the last 24 h including a decaying period after 00:00 UTC, 10 August. Due to the interaction of typhoon and topography, the vertical wind and precipitation increase after 12:00 UTC, 9 August and produce another peak around 00:00 UTC, 10 August when outer rainbands reach Taiwan, as shown recently by Jang and Chun (2013). Correlation between the vertical velocity and HDTGW at 16 km a.g.l.…”

Mapping and Analyzing the Evolution of the Butangbunasi Landslide Using Landsat Time Series with Respect to Heavy Rainfall Events during Typhoons

“…The mountains of Taiwan, with the highest peaks rising to almost 4000 m a.s.l., are characterized by fractured rock formations, high relief and steep stream gradients. These mountains, particularly the central mountain range (CMR), influence the tracks and intensity of typhoon events [1]. During summer and autumn, Taiwan is regularly affected by typhoons (tropical cyclones), three to four per year on average, which bring heavy rainfall [2].…”