碩士 / 國立臺灣大學 / 大氣科學研究所 / 106 / This study investigates convective lines developing around Taiwan under the environment of Typhoon Soudelor, Sinlaku, and Hagupit using radar data from Wufenshan (WFS), Hualien (RCHL), Kenting (RCKT), and surface observations from Central Weather Bureau and Green Island radar of the Air Force Weather Wing, and Yonaguni surface observations of Japan Meteorological Agency. This research analyzes the three-dimensional characteristics of the precipitation structure in the convective line through dual-Doppler analysis for the three cases(RSOU, RSIN, RHA)and compared with the structure of squall line.
For the cases study, the large environment are affected mainly by the typhoon’s outer circulations when the convective lines develop. Coastal wind analyes show no obvious diurnal variation in offshore flow(onshore flow). Furthermore, the area of high Convective Available Potential Energy (CAPE) near Ishigaki Island, Japan matches the generation area of the convective lines. There convective lines weaken near the coast of Taiwan, consistent with characteristic of smaller CAPE near the shore. On the other hand, the pressure ridge along the eastern Taiwan deepens as the convective lines approach the eastern coast of Taiwan, and weaken as the convective lines dissipate.
The dual-Doppler radar analysis shows unique characteristics for each case. All three convective lines have convective precipitation without obvious stratiform precipitation. The internal kinematic circulations are also different. For R HA , the convective zone is dominated by Front-to-rear (FTR) flow that is lifted over the region of heavy precipitation. There is only a deep layer of either FTR or rear-to-front (RTF) flow lifted in the convective zone of R SIN . However, FTR and RTF converge in the convective zone for RSOU , an air flow pattern similar to squall-line’s structure documented previously.However, the maximum vertical velocities associated with RSOU , RSIN , RHA(~2 ms-1) are much smaller than the typical vertical velocity of squall line (~10 m s -1 ).
During the passage of the R SOU and R SIN , the surface perturbation pressure(P’) and cross-band wind(Vc) show the feature of the gravity wave, whereas there is no obvious wave characteristic in the P’ and Vc for R HA . After comparing the phase speeds of internal and inertia gravity waves with the cases, it can be concluded that the two are not identical.
| Identifer | oai:union.ndltd.org:TW/106NTU05022023 |
| Date | January 2018 |
| Creators | Jia-Ming Yan, 嚴嘉明 |
| Contributors | Cheng-Ku Yu, 游政谷 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 101 |
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