地球惑星科学専攻 地球科学輻合部特別講演会
 
日時: 2011年7月27日(水) 16:00〜17:00
場所: 京都大学理学部1号館5階563号室
 

講演題名：
Roles of Mesoscale Convective Systems in Tropical Cyclone Formations: A Numerical Study of Typhoon Ketsana (2003)
 
講演者：
Dr. Kevin K. W. Cheung 
(Senior Lecturer, Department of Environment and Geography, Macquarie University, Sydney, Australia)
 
講演要旨：
Tropical cyclone (TC) formation is still one of the mysteries in tropical meteorology, and represents a substantial 
challenge for numerical guidance. After reviewing some recent theories of TC formation, this talk will present results 
from a case study that focuses on the effects of multiple mesoscale convective systems (MCSs) on the formation of 
Typhoon Ketsana (2003). Numerical simulations using the Weather Research and Forecast (WRF) model with assimilation of 
QuikSCAT and SSM/I oceanic winds and total precipitable water are performed. The WRF model simulates well the convective 
episodes associated with the MCSs and the formation time and location of Typhoon Ketsana. With the successive occurrence 
of MCSs, mid-level average relative vorticity is strengthened through generation of mesoscale convective vortices (MCVs) 
mainly via the vertical stretching mechanism. Scale separation shows that the activity of the vortical hot tower 
(VHT)-type meso-γ-scale vortices is closely related to the development of the MCSs. These VHTs have large values of 
positive relative vorticity induced by intense low-level convergence, and thus play an important role in the low-level 
vortex enhancement with aggregation of VHTs as one of the possible mechanisms. Four sensitivity experiments are performed 
to analyze the possible different roles of the MCSs during the formation of Typhoon Ketsana by modifying the vertical 
relative humidity profile in each of the MCSs. The results show that the development of a MCS depends substantially on 
that of the prior ones, and thus leading to different scenarios of system intensification during the TC formation. The 
earlier MCSs are responsible for the first stage vortex enhancement, and depending on the location can affect quite 
largely the simulated formation location. The extreme convection within the last MCS before formation is determining the 
final route to the TC formation, and consequently the formation time as well.
 
 
問い合わせ先：
余田 成男