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| Titel |
The impact of cloud radiative heating on the Madden-Julian Oscillation |
| VerfasserIn |
Traute Crueger, Bjorn Stevens |
| 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 |
250102991
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| Publikation (Nr.) |
 EGU/EGU2015-2691.pdf |
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| Zusammenfassung |
| We explore how atmospheric radiative heating, due to the presence of clouds, influences the
Madden-Julian-Oscillation (MJO) as simulated by four comprehensive atmosphere general
circulation models. For that reason we compare simulations in which clouds are transparent
to electromagnetic radiation (“clouds-off”) with control simulations in which clouds are
allowed to interact with radiation (“clouds-on"). Making clouds transparent to radiation
leads to robust changes of the mean state and the MJO: tropical precipitation in
the Indian ocean is displaced off the equator, leading to two symmetric bands of
precipitation in this basin. In addition, in clouds-off, the MJO weakens compared to
clouds-on.
Within the MJO cloud radiative effects lead to stronger convective heating profiles.
Heating from non-radiative processes is dominated by the parameterized convection,
but large-scale heating associated with cloud microphysical processes acting on
the grid-scale, modifies the shape of the profile, leading to a top-heaviness when
cloud radiative effects are accounted for. The radiative heating due to clouds slows
down the phase speed of the MJO. Averaged over the entire MJO life-cycle the
column-integrated radiative heating due to clouds lags the vertically integrated moist static
energy by 40° to 60° of longitude (equivalently 7 to 10 days assuming a period of 60
days).
All four models studied reveal more pronounced Kelvin waves when clouds are
transparent to radiation (clouds-off) suggesting that cloud-radiative effects on large-scale
heating profiles acts to damp smaller scale, or faster, Convectively Coupled Equatorial Waves
and amplify MJO-like disturbances. |
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