Geography Reference
In-Depth Information
Figure 4.2
Maps of the cyclone hazard in the South China Sea area: (A) percentage chance of a cyclone
entering the China Sea affecting different 2×2 degree grid squares; (B) the size of reduction in cyclone
frequency (six-hour periods per year) in an ENSO year for 2×2 degree grid squares in the China Sea area.
Source:
After McGregor 1995.
of the percentage probability that any tropical
cyclone entering the South China Sea would pass
through any given square (Figure 4.2A). A
WNW—ESE oriented zone of peak probability
was identified stretching from Hainan,
Guangdong and Hong Kong in southern China
to central Luzon in the Phillipines. The study also
demonstrated how cyclone activity in the region
was greatly reduced in all ENSO years during the
period (Figure 4.2B), a pattern also found in the
Caribbean (Eyre and Gray 1990; Gray and
Sheaffer 1991).
climatic modellers have suggested (e.g. Emanuel
1987). To overcome the problem of increasingly
incomplete records back through time, analyses
have been restricted to those parts of a
macroregion with longer periods of
comprehensive data. Figure 4.3 updates to 1995
analyses carried out by several geographers of
cyclone frequency for a 5°×5° grid-square matrix
covering the western part of the North Atlantic/
Caribbean macroregion using US Weather Bureau
charts of cyclone tracks since 1871 (Spencer and
Douglas 1985; Walsh and Reading 1991; Reading
and Walsh 1995). Regional cyclone frequency was
high in 1871-1901 and in 1928-58 but low in
1902-27 and from 1959 to the 1990s, but the
spatial distributions of activity in the two peaks
and the two troughs differed markedly. Temporal
fluctuations varied greatly between different 5°
squares (Figure 4.4). Along the Texan coast,
cyclone frequency peaked in the late nineteenth
century, whereas in Florida and the northern
Lesser Antilles frequencies peaked in 1928-58. In
Spatiotemporal changes in cyclone
magnitude and frequency
Several geographical studies have examined recent
or historical changes in the frequency and tracks
of cyclones and assessed the question of whether
or not global warming, via higher sea-surface
temperatures, will result in increased cyclone
frequency or severity, as some climatologists and
