Using Synthetic Brightness Temperatures to Address Uncertainties in Cloud-Top-Height Verification

Cloud-top verification is inherently difficult because of large uncertainties in the estimates of observed cloud-top height. Misplacement of cloud top associated with transmittance through optically thin cirrus is one of the most common problems. Forward radiative models permit a direct comparison o...

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Bibliographic Details
Published in:Journal of applied meteorology and climatology 2017-02, Vol.56 (2), p.283-296
Main Authors: Nachamkin, Jason E., Jin, Yi, Grasso, Lewis D., Richardson, Kim
Format: Article
Language:English
Subjects:
Brightness
Brightness temperature
Cirrus clouds
Cloud cover
Clouds
Computer simulation
Convection
Diagnosis
Errors
Filters
Height
Ice
Ice clouds
Laboratories
Meteorological satellites
Radiance
Simulation
Statistical analysis
Statistical methods
Stratus clouds
Temperature
Transmittance
Trends
Vertical orientation
Weather forecasting
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Summary:Cloud-top verification is inherently difficult because of large uncertainties in the estimates of observed cloud-top height. Misplacement of cloud top associated with transmittance through optically thin cirrus is one of the most common problems. Forward radiative models permit a direct comparison of predicted and observed radiance, but uncertainties in the vertical position of clouds remain. In this work, synthetic brightness temperatures are compared with forecast cloud-top heights so as to investigate potential errors and develop filters to remove optically thin ice clouds. Results from a statistical analysis reveal that up to 50% of the clouds with brightness temperatures as high as 280 K are actually optically thin cirrus. The filters successfully removed most of the thin ice clouds, allowing for the diagnosis of very specific errors. The results indicate a strong negative bias in midtropospheric cloud cover in the model, as well as a lack of land-based convective cumuliform clouds. The model also predicted an area of persistent stratus over the North Atlantic Ocean that was not apparent in the observations. In contrast, high cloud tops associated with deep convection were well simulated, as were mesoscale areas of enhanced trade cumulus coverage in the Sargasso Sea.
ISSN:1558-8424
1558-8432
DOI:10.1175/JAMC-D-16-0240.1