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| Titel |
Scale-by-scale analysis of probability distributions for global MODIS-AQUA cloud properties: how the large scale signature of turbulence may impact statistical analyses of clouds |
| VerfasserIn |
M. Torre Juárez, A. B. Davis, E. J. Fetzer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 6 ; Nr. 11, no. 6 (2011-03-28), S.2893-2901 |
| Datensatznummer |
250009528
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| Publikation (Nr.) |
 copernicus.org/acp-11-2893-2011.pdf |
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| Zusammenfassung |
| Means, standard deviations, homogeneity parameters used in models based
on their ratio, and the probability distribution functions (PDFs) of cloud
properties from the MODerate resolution Infrared Spectrometer (MODIS) are
estimated globally as function of averaging scale varying from 5 to 500 km.
The properties – cloud fraction, droplet effective radius, and liquid
water path – all matter for cloud-climate uncertainty quantification and
reduction efforts. Global means and standard deviations are confirmed to
change with scale. For the range of scales considered, global means vary only
within 3% for cloud fraction, 7% for liquid water path, and 0.2% for cloud
particle effective radius. These scale dependences contribute to the
uncertainties in their global budgets. Scale dependence for standard
deviations and generalized flatness are compared to predictions for turbulent
systems. Analytical expressions are identified that fit best to each observed
PDF. While the best analytical PDF fit to each variable differs, all
PDFs are well described by log-normal PDFs when the mean is normalized by the
standard deviation inside each averaging domain. Importantly, log-normal
distributions yield significantly better fits to the observations than
gaussians at all scales. This suggests a possible approach for both sub-grid
and unified stochastic modeling of these variables at all scales. The results
also highlight the need to establish an adequate spatial resolution for
two-stream radiative studies of cloud-climate interactions. |
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