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| Titel |
Environmental Influences on the Intensity Changes of Tropical Cyclones over the Western North Pacific |
| VerfasserIn |
Shoujuan Shu, Fuqing Zhang, Yuan Wang |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104837
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| Publikation (Nr.) |
 EGU/EGU2015-4276.pdf |
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| Zusammenfassung |
| The influence of environmental conditions on the intensity changes of tropical cyclones (TCs)
over the western North Pacific (WNP) is investigated through examination of 37 TCs during
2000-2011 that interacted directly with the western North Pacific subtropical high
(WNPSH). Comprehensive composite analysis of the environmental conditions
is performed for two stages of storms: one is categorized as intensifying events
(maximum wind speed increases by 15 kts over 48 h) and the other is categorized as
weakening events (maximum wind speed decreases by 15 kts over 48 h). Comparison
of the composite analysis of these two cases show that environmental conditions
associated with the WNPSH play important roles in the intensity changes of TCs over
the WNP. When a TC moves along the southern periphery of the WNPSH, the
relatively weaker easterly environmental vertical wind shear helps bring warm moist air
from the south and southeast to its southeast quadrant within 500 km , which is
favourable for the TC to intensify. On the other hand, when a TC moves along the
western edge of the WNPSH, under the combined influences of the WNPSH and an
upper-level westerly trough, a strong westerly vertical shear promotes the intrusion of dry
environmental air associated with the WNPSH from the north and northwest, which
may lead to the inhibition of moisture supply and convection over the west half of
the TC and thus its weakening. These composite results are consistent with those
with additonal geographic restrictions, suggesting that the dry air intrusion and the
vertical wind shear (VWS) associated with the WNPSH, indeed affect the intensity
changes of TCs over the WNP beyond the difference related solely to variations in
geographical locations. The average sea surface temperature (SST) of 27.6° for
the weakening events is also lower than an average of 28.9° for the strengthening
events, but remains above the critical value of 27° for TC intensification, suggesting
that the SST may be regarded as a less positive factor for the weakening events. |
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