J4.1 Satellite Remote Sensing of Cloud-base Updrafts for Marine Stratocumulus

Tuesday, 24 January 2017: 10:30 AM
612 (Washington State Convention Center )
Youtong Zheng, University of Maryland, College Park, MD; and D. Rosenfeld and Z. Li

Handout (1.0 MB)

Updraft speeds at cloud base (Wb) have always been notoriously difficult to measure, despite significant roles they play in cloud formation and precipitation. Resently, methods of satellite-retrieval of Wb for convective clouds were proposed. However, method of satellite retrieving Wb for stratocumulus is still misssing despite the significant role stratocumulus plays in Earth's radiation budget. In this study, a statistically significant relationship between Wb and cloud-top radiative cooling rate (CTRC) is found from the measurements of the Department of Energy’s Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) on board a ship sailing between Honolulu and Los Angeles has documented. A similar relation was found on the Graciosa Island, but with greater scatter and weaker correlation presumably due to perturbation of island effect. Based on the relation, we are able to estimate the cloud-base updrafts using a simple formula: Wb = -0.43*CTRC + 22.46 ±13, where the Wb and CTRC have the units of cm/s and W/m2, respectively. This relationship was applied to satellite retrieval of Wfor stratocumulus, which uses satellite- and reanalysis-derived parameters to calcuate the CTRC and therefore infer the Wb.
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