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| Titel |
Scale dependency of total water variance, and its implication for cloud parameterizations |
| VerfasserIn |
Vera Schemann, Bjorn Stevens, Verena Grützun, Johannes Quaas |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083501
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| Zusammenfassung |
| Cloud process and cloud cover parameterizations are known to be a main driver of uncertainties in
simulations of climate change. All parameterizations rest on the representation of subgrid-scale
variability of total water. With the ongoing increase in resolution and the new opportunities to use
grid refinement, the question of scale (in)dependency of parameterizations becomes more
important.
In this study the scale dependency of variance of total water mixing ratio is explored by analyzing
data from a General Circulation Model (ECHAM6), a Numerical Weather Prediction Model
(COSMO-DE and COSMO-EU) and Large Eddy Simulations (UCLALES). Additionally data from
Direct Numerical Simulations is included. The aim is to define a general scaling law, which can be
used to evaluate and improve cloud process parameterizations. Especially the large scale models
(ECHAM6 and COSMO-DE/EU) show a consistent and continuous scaling around a power law
exponent of -2. The scaling continues also for the higher resolution datasets but the variability of
the scaling exponent increases. Nevertheless neither a spectral gap nor a strong scale break was
found. This is of special interest for the transition between resolved and parameterized scales in a
general circulation model. The results point out the need for scale dependent cloud process
parameterizations. As a first step in this direction the evaluation of the parameterized total water
variance of a state of the art statistical scheme is also presented. |
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