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Published March 2016 | Published
Journal Article Open

Stratocumulus Cloud Clearings and Notable Thermodynamic and Aerosol Contrasts across the Clear–Cloudy Interface


Data from three research flights, conducted over water near the California coast, are used to investigate the boundary between stratocumulus cloud decks and clearings of different sizes. Large clearings exhibit a diurnal cycle with growth during the day and contraction overnight and a multiday life cycle that can include oscillations between growth and decay, whereas a small coastal clearing was observed to be locally confined with a subdiurnal lifetime. Subcloud aerosol characteristics are similar on both sides of the clear–cloudy boundary in the three cases, while meteorological properties exhibit subtle, yet important, gradients, implying that dynamics, and not microphysics, is the primary driver for the clearing characteristics. Transects, made at multiple levels across the cloud boundary during one flight, highlight the importance of microscale (~1 km) structure in thermodynamic properties near the cloud edge, suggesting that dynamic forcing at length scales comparable to the convective eddy scale may be influential to the larger-scale characteristics of the clearing. These results have implications for modeling and observational studies of marine boundary layer clouds, especially in relation to aerosol–cloud interactions and scales of variability responsible for the evolution of stratocumulus clearings.

Additional Information

© 2016 American Meteorological Society. Manuscript received 18 May 2015, in final form 26 November 2015. All data used can be obtained from the corresponding author. This work was funded by NASA Grant NNX14AM02G and ONR Grants N00014-11-1-0783, N00014-10-1-0200, and N00014-10-1-0811. JSC acknowledges support from Dreyfus Award EP-11-117. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and READY website (http://ready.arl.noaa.gov) used in this publication. Some of the analyses and visualizations used in this study were produced with the Giovanni online data system, developed and maintained by the NASA GES DISC.

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October 18, 2023