Document Type

Article

Publication Date

10-16-2015

Publication Title

Geophysical Research Letters

Abstract

High-resolution ground-based measurements are used to assess the realism of fine-scale numerical simulations of shallow cumulus cloud fields. The overlap statistics of cumuli as produced by large-eddy simulations (LES) are confronted with Cloudnet data sets at the Jülich Observatory for Cloud Evolution. The Cloudnet pixel is small enough to detect cumuliform cloud overlap. Cloud fraction masks are derived for five different cases, using gridded time-height data sets at various temporal and vertical resolutions. The overlap ratio (R), i.e., the ratio between cloud fraction by volume and by area, is studied as a function of the vertical resolution. Good agreement is found between R derived from observations and simulations. An inverse linear function is found to best describe the observed overlap behavior, confirming previous LES results. Simulated and observed decorrelation lengths are smaller (∼300 m) than previously reported (>1 km). A similar diurnal variation in the overlap efficiency is found in observations and simulations.

Comments

This research has been jointly financed by the Federal Ministry of Education and Research (BMBF) within the programme High Definition Clouds and Precipitation for advancing Climate Predic tion (HD(CP)2) under grant HD(CP)2 01LK1209A and ITARS(www.itars.net), European Union Seventh Framework Programme FP7: People, and ITN Marie SklodowskaCurie Actions Programme under grant agreement 289923.

DOI

10.1002/2015GL065140

Version

Publisher's PDF

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Volume

42

Issue

19

Included in

Physics Commons

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