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| Titel |
Origin of the interannual variability of tropical cyclones activity in the South Pacific |
| VerfasserIn |
Nicolas C. Jourdain, Patrick Marchesiello, Christophe E. Menkes, Jérome Lefèvre, Emmanuel M. Vincent, Matthieu Lengaigne, Fabrice Chauvin |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033685
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| Zusammenfassung |
| The Weather Research and Forecast model (WRF, Skamarock et al., 2005) is used at 1/3°
(150Â km effective) resolution to simulate the statistics of tropical cyclone activity in the
South Pacific. Our first aim is to realistically represent the climatological conditions favorable
to tropical cyclone genesis, in particular the characteristics of the South Pacific
Convergence Zone (SPCZ). This is achieved by selecting a subgrid-scale convective
parametrization. In addition to the large-scale conditions, the model is shown to
reproduce a wide range of mesoscale convective systems. Tropical cyclones grow
from the most intense of these systems formed along SPCZ lines of strengthened
convergence and sometimes develop into hurricanes with surface winds of up to
45Â m.s-1. The 3-dimensional structure of simulated tropical cyclones is in remarkable
agreement with dropsondes and satellite observations. The mean seasonal and spatial
distributions of tropical cyclone genesis and occurrence are also in relatively good
agreement with the Joint Typhoon Warning Center data. We note however that the
spatial pattern of tropical cyclone genesis exhibits a similar bias as the large scale
forcing.
Previous work have shown that the seasonal frequency of tropical cyclone genesis at any
location is closely related to large scale environmental parameters (Gray, 1979; Royer et al.,
1998; Camargo et al., 2007). However, large scale conditions are not sufficient and triggering
mechanisms are also needed. Indeed, interactions of mesoscale convective systems play a
crucial role in tropical cyclone genesis once the large scales have been established
(Simpson et al., 1997). Our objective is to estimate the part of tropical cyclone genesis
interannual variability that is related to large scale environmental parameters, and
the part that is due to mesoscale interactions that are stochastic in nature. We use
a 10-member ensemble WRF experiment, genesis indices, and ENSO (El Niño
southern oscillation) and SPCZ indices to get such an estimate in the South Pacific. |
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