地球惑星科学専攻　地球科学輻合部特別講演会

日時: 平成２５年４月３０日（火）１０：００　～　１２：００
場所：京都大学 理学研究科１号館５階５６３号室

講演題名：
Is Record-Breaking Increase in Taiwan Typhoon Rainfall Related to Global
Warming?

講演者：
Professor Dr. Chih-Pei Chang
     (Dept. of Atmos. Sci., National Taiwan Univ., Taiwan /
      Dept. of Meteorology, Naval Postgraduate School, U.S.A.)

講演要旨：
    Taiwan has experienced a series of TCs with extraordinary amount of
rainfall since the late 1990s. In addition to an increase in the numbers,
nine of the top 12 typhoons in total rainfall since hourly rainfall
observations started in 1960 have occurred in the 21st century.
The most extreme case is the record-breaking Typhoon Morakot in 2009 that
caused huge economic and life losses, and became the first natural disaster
in Taiwan that actually triggered a change of government.
Whether the heavy rainfall associated of these heavy rainfall typhoons is an
impact of global warming, and in particular whether global warming-enhanced
water vapor capacity caused a positive interaction between water vapor
supply and TC that led to the observed large increasing trend of heavy
rainfall, is the subject of intense debate.
    Here we show that the increasing trend of typhoon related intense
rainfall in the last half Century is a local anomaly in the China summer
monsoon region, and that most of the recently observed large increase in
typhoon rainfall is the result of slowly moving TCs and 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 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.

問い合わせ先： 余田　成男