Geographically versus dynamically defined boundary layer cloud regimes and their use to evaluate general circulation model cloud parameterizations

Regimes of tropical low‐level clouds are commonly identified according to large‐scale subsidence and lower tropospheric stability (LTS). This definition alone is insufficient for the distinction between regimes and limits the comparison of low‐level clouds from CloudSat radar observations and the EC...

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Bibliographic Details
Published in:Geophysical research letters 2013-09, Vol.40 (18), p.4951-4956
Main Authors: Nam, Christine C.W., Quaas, Johannes
Format: Article
Language:English
Subjects:
Altitude
Atmospheric stability
boundary layer clouds
Boundary layers
Circulation
Clouds
CloudSat
Computer simulation
Contamination
COSP
Cumulus clouds
Dynamic tests
Earth sciences
Earth, ocean, space
ECHAM5
Evaluation
Exact sciences and technology
General circulation
General circulation models
Histograms
Hydrometeors
Identification
Parametrization
Profiles
Radar
radar simulator
Reflectance
Reflectivity
Regional
Regional analysis
Simulation
Simulators
Stability
Stratocumulus clouds
Subsidence
Tropical climate
tropical low clouds
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Summary:Regimes of tropical low‐level clouds are commonly identified according to large‐scale subsidence and lower tropospheric stability (LTS). This definition alone is insufficient for the distinction between regimes and limits the comparison of low‐level clouds from CloudSat radar observations and the ECHAM5 GCM run with the COSP radar simulator. Comparisons of CloudSat radar cloud altitude‐reflectivity histograms for stratocumulus and shallow cumulus regimes, as defined above, show nearly identical reflectivity profiles, because the distinction between the two regimes is dependent upon atmospheric stability below 700 hPa and observations above 1.5 km. Regional subsets, near California and Hawaii, for example, have large differences in reflectivity profiles than the dynamically defined domain; indicating different reflectivity profiles exist under a given large‐scale environment. Regional subsets are better for the evaluation of low‐level clouds in CloudSat and ECHAM5 as there is less contamination between 2.5 km and 7.5 km from precipitating hydrometeors which obscured cloud reflectivities. Key Points Identification of low clouds by large‐scale dynamics insufficient for radarStratocumulus and shallow cumulus regimes have nearly identical reflectivitiesGeographical regions are better for evaluating low-level clouds with a radar
ISSN:0094-8276
1944-8007
DOI:10.1002/grl.50945