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| Titel |
Relationships between wind speed, humidity and precipitating shallow convection |
| VerfasserIn |
L. Nuijens, B. Stevens |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022661
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| Zusammenfassung |
| Precipitation from shallow cumulus is observed to be a frequent phenomenon over
subtropical oceans, yet ignored in most theories that describe shallow cumulus
convection and its bulk characteristics. It is questioned what factors control
variability of precipitation in a typical undisturbed trade-wind regime and how
precipitation relates to cloud behavior and mean boundary layer characteristics.
Two-months of observations suggest that even within such a meteorological regime
subtle fluctuations in the strength of the easterlies and in subsidence play a
major role in regulating boundary layer humidity, hence clouds and
precipitation. In particular the covariability between wind speed, humidity and
precipitation stands out, with interesting similarities to cases of
precipitating deep convection. It is hypothesized that stronger winds, through
enhanced surface evaporation and upward mixing of moisture, lead to more and on
average deeper cumuli that rain more. Possible aerosol effects on large-scale
precipitation occurrence, through an influence of wind speed on wave-breaking
and sea-salt aerosol concentrations, likely play a minor role. Large-eddy
simulation (LES) studies are used to explore the idea that the observed
wind speed - precipitation relationship resides in a change in macroscopic cloud
properties. |
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