Title page for etd-0611117-125623


[Back to Results | New Search]

URN etd-0611117-125623
Author Yi-Ting Cheng
Author's Email Address z123456776@yahoo.com.tw
Statistics This thesis had been viewed 5359 times. Download 570 times.
Department Department of Oceanography
Year 2016
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Cyclonic Eddies Induced by Global Super typhoons
Date of Defense 2017-06-01
Page Count 110
Keyword
  • drifter
  • absolute geostrophic velocity
  • sea surface height
  • mesoscale cyclonic eddy
  • super typhoon
  • Abstract According to Geisler’s classic theory (1970), when the phase speed of the first baroclinic mode c1 exceeds the tropical cyclone’s (TC) translation speed Uh (Uh /c1 < 1, slow-moving), the oceanic response is a barotropic, geostrophical, and cyclonic gyre with upwelling in the storm’s center. Following Geisler’s theory (1970), this study analyzed data from drifters of the Surface Velocity Program (SVP), satellite altimeter measurements, and global typhoons from Joint Typhoon Warning Center during 1993-2015 to investigate mesoscale cyclonic eddies induced by slow-moving super typhoons.
    Our results show that 22 slow-moving super typhoons can be found globally in this period, among them only seven typhoons produced or strengthened mesoscale cyclonic eddies (3 in Northern Hemisphere, and 4 in Southern Hemisphere). These TCs have several properties in common: [1] mean Uh is less than 2 m/s, [2] slow-moving condition (Uh /c1 < 1) lasts for at least 12 hours, [3] pass the open ocean (without land effect). Strong current speed of TC-eddies over 2 m/s were observed, and these eddies propagated westward for a period of one to eight months. Compared with the North Pacific Subtropical Counter Current (STCC) eddies, the TC-eddies have a life span of about 1.3 times of the STCC eddies, while mean radius is 1.0-1.8 times, eddy kinetic energy (EKE) is 3-16 times, and current speed is 1.1-1.8 times of the STCC eddies.
    For the TC Nida-eddy, the SST shows a temperature drop of 2.5-3.5oC as observed by SVP drifters. A 30-m increase of the mixed-layer depth was also found from Global Temperature and Salinity Profile Programme data at a region in the north Pacific Ocean when Nida passed by. After Nida disappeared, the cyclonic eddy became strengthened and the thermocline was moved upward, indicating the formation of upwelling.
    Analysis of eddy’s EKE and TC’s translation speed reveal a negative correlation between these two quantities. Under the same TC’s maximum wind speed, as the TC’s translation speed is slower, the induced TC-eddy will have a higher EKE. The opposite is also true.
    Advisory Committee
  • Guan-Yu Chen - chair
  • Yu-Chia Chang - co-chair
  • Chun-Hoe Chow - co-chair
  • I-Huan Lee - co-chair
  • Ruo-Shan Tseng - advisor
  • Files
  • etd-0611117-125623.pdf
  • indicate access worldwide
    Date of Submission 2017-07-18

    [Back to Results | New Search]


    Browse | Search All Available ETDs

    If you have more questions or technical problems, please contact eThesys