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| Titel |
The effect of Arabian Sea optical properties on SST biases and the South Asian summer monsoon in a coupled GCM |
| VerfasserIn |
A. G. Turner, M. Joshi, E. S. Robertson, S. J. Woolnough |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066069
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| Zusammenfassung |
| This study examines the effect of seasonally varying chlorophyll on the climate of the
Arabian Sea and South Asian monsoon. The effect of such seasonality on the radiative
properties of the upper ocean is often a missing process in coupled general circulation models
and its large amplitude in the region makes it a pertinent choice for study to determine any
impact on systematic biases in the mean and seasonality of the Arabian Sea. In this
study we examine the effects of incorporating a seasonal cycle in chlorophyll due
to phytoplankton blooms in the UK Met Office coupled atmosphere-ocean GCM
HadCM3. This is achieved by performing experiments in which the optical properties of
water in the Arabian Sea — a key signal of the semi-annual cycle of phytoplankton
blooms in the region — are calculated from a chlorophyll climatology derived from
Sea-viewing Wide Field-of-View Sensor (SeaWiFS) data. The SeaWiFS chlorophyll
is prescribed in annual mean and seasonally-varying experiments. In response to
the chlorophyll bloom in late spring, biases in mixed layer depth are reduced by
up to 50% and the surface is warmed, leading to increases in monsoon rainfall
during the onset period. However when the monsoons are fully established in boreal
winter and summer and there are strong surface winds and a deep mixed layer,
biases in the mixed layer depth are reduced but the surface undergoes cooling. The
seasonality of the response of SST to chlorophyll is found to depend on the relative
depth of the mixed layer to that of the anomalous penetration depth of solar fluxes.
Thus the inclusion of the effects of chlorophyll on radiative properties of the upper
ocean acts to reduce biases in mixed layer depth and increase seasonality in SST. |
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