7.6.5.2 ENSO and tropical storms
Any changes in ENSO as the climate changes will impact the distribution and
tracks of tropical cyclones (including intense storms such as hurricanes and
typhoons). During an El Niño, for example, the incidence of hurricanes
typically decreases in the Atlantic and far western Pacific and Australian regions,
but increases in the central and eastern Pacific (Lander, 1994). Thus it should
be recognised that decreases in one area may be offset by increases in another
area because of the global connectivity of the tropical atmospheric circulation.
Global warming from increasing greenhouse gases in the atmosphere suggests increased
convective activity but there is a possible trade-off between individual versus
organised convection. While increases in sea surface temperatures favour more
and stronger tropical cyclones, increased isolated convection stabilises the
tropical troposphere and this in turn suppresses organised convection making
it less favourable for vigorous tropical cyclones to develop (Yoshimura et al.,
1999). Thus changes in atmospheric stability (Bengtsson et al., 1996) and circulation
may produce offsetting tendencies (e.g., Royer et al., 1998). General circulation
models of the atmosphere (see Chapter 8, Section
8.8.4) do not resolve the scales required to properly address this issue;
for instance, moist convection and hurricanes are not resolved adequately.
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