Stratocumulous-to-Cumulous Transition

Stratocumulus-to-Cumulous Transition

© Youtong Zheng

CICS-MD Scientist Youtong Zheng, who works with Prof. Zhanqing Li on his JPSS PGRR-funded CICS task on satellite cloud-base height retrievals, has new a new article accepted by Geophysical Research Letters and posted online on July 23. The article looks at the “Decoupling Degree” of stratocumulus decks, a key variable in the evolution of these clouds. In the subtropical region, decoupling is an intermediate process in stratocumulus-to-cumulus transitions, a persistent phenomenon that is not fully understood. The Decoupling Degree in the study is defined as the difference between the stratocumulus cloud-base height and the lifting condensation level (LCL), determined by the cumulus cloud-base height under cold-advection conditions.

The schematic above shows the decoupling process and its measurability through its link to the skewness of the Liquid Water Path (LWP) Probability Distribution Function (PDF). Using measurements from passive satellite sensors, the researchers were able to confirm the theory that decoupled stratocumulus clouds under cold-advection conditions are fed by spreading of the tops of cumulus clouds to which they are coupled.  Zheng, Youtong, Daniel Rosenfeld and Zhanqing Li, 2018: Estimating the decoupling degree of subtropical marine stratocumulus decks from satellite, Geophys. Res. Lett., https://doi.org/10.1029/2018GL078382, accepted.

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