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| Titel |
Influence of the land-atmosphere coupling on cloud development and precipitation over Southeastern Brazil |
| VerfasserIn |
Daniela Carneiro Rodrigues, Sin Chan Chou |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250152336
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| Publikation (Nr.) |
 EGU/EGU2017-17160.pdf |
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| Zusammenfassung |
| The processes of interaction between the land surface and the atmosphere may play an
important role in mesoscale convection and precipitation. Numerical weather and climate
prediction models still do not correctly represent surface-to-atmosphere changes. The
objective of this study is to investigate the influence of the land surface-to-atmosphere
coupling on cloud development and convective precipitation over the Southeast region of
Brazil. The effects of the land-atmosphere coupling are analyzed through simulations with
the Eta regional model in very high spatial resolution (1 km), using the NOAH surface
scheme. Different values were tested for the Zilitinkevich coefficient (Czil) which partitions
the heat/moisture and momentum roughness lengths and indirectly determine the
coupling force between the land surface and the atmosphere. The results showed that
improvements in the precipitation simulation can be obtained by changing the value of the
surface-to-atmosphere exchange coefficient. Changes in parameter values impact partitioning
of surface flows resulting in changes in atmospheric fields near the surface. We have found
that in general the increase in Czil leads to a decrease in latent and sensitive heat fluxes and,
consequently, causes an increase in surface temperature. A decrease in surface temperature
was observed in tropical forest areas when the value of the Czil coefficient was
dynamically varied as a function of the height of the vegetation. The substitution of the
default value (0.2) for the value of 0.8 and values that vary dynamically due to
the roughness of the vegetation cover showed the best results in the simulation of
the precipitation event. These values decreased precipitation overestimates and
increased their amount in regions where it was underestimated. Improvements in the
simulation of surface fluxes and in the atmospheric field were obtained by adopting
the dynamic coupling coefficient. The tests need to be analyzed for other regions.
The results support the use of a dynamic coupling formulation, but caution about
complex terrain should be taken. Overall, these results point out that the evaluation and
enhancement of the land-to-atmosphere coupling could potentially improve the
performance of the model in simulation of convective clouds and precipitation. |
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