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Simulated Convective Invigoration Processes at Trade Wind Cumulus Cold Pool Boundaries

Simulated Convective Invigoration Processes at Trade Wind Cumulus Cold Pool Boundaries Observations of precipitating trade wind cumuli show convective invigoration on the downwind side of their cold pools. The authors study convection and cold pools using a nested–Weather Research and Forecasting Model simulation of 19 January 2005—a day from the Rain in Cumulus over the Ocean experiment. The temperature and water vapor mixing ratio drops in simulated cold pools fall within the envelope of observed cases, and the wind enhancement matches observations more closely. Subcloud updrafts downwind and near the cold pool boundary are statistically compared to updrafts further from cold pools. Updrafts near cold pool outflows are moister than the other updrafts and are more likely to originate from overall moister regions. Cold pool–influenced updrafts tend to exceed the other updrafts in vertical velocity and are associated with more cloud liquid water. The strength of circulation within the cold pool boundary is unable to match that because of the low-level environmental wind shear, and the lifted updrafts advect faster than the environmental wind, thereby accessing the ambient environmental moisture converged by cold pool expansion. Cases with higher rain rates correspond to larger cloud cover through the shearing off of the upper-level cloud, consistent with observations. This study suggests that it is the ability of cold pools to lift thermodynamically favorable air that is critical for secondary convection of trade wind cumuli. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

Simulated Convective Invigoration Processes at Trade Wind Cumulus Cold Pool Boundaries

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Publisher
American Meteorological Society
Copyright
Copyright © 2013 American Meteorological Society
ISSN
0022-4928
eISSN
1520-0469
DOI
10.1175/JAS-D-13-0184.1
Publisher site
See Article on Publisher Site

Abstract

Observations of precipitating trade wind cumuli show convective invigoration on the downwind side of their cold pools. The authors study convection and cold pools using a nested–Weather Research and Forecasting Model simulation of 19 January 2005—a day from the Rain in Cumulus over the Ocean experiment. The temperature and water vapor mixing ratio drops in simulated cold pools fall within the envelope of observed cases, and the wind enhancement matches observations more closely. Subcloud updrafts downwind and near the cold pool boundary are statistically compared to updrafts further from cold pools. Updrafts near cold pool outflows are moister than the other updrafts and are more likely to originate from overall moister regions. Cold pool–influenced updrafts tend to exceed the other updrafts in vertical velocity and are associated with more cloud liquid water. The strength of circulation within the cold pool boundary is unable to match that because of the low-level environmental wind shear, and the lifted updrafts advect faster than the environmental wind, thereby accessing the ambient environmental moisture converged by cold pool expansion. Cases with higher rain rates correspond to larger cloud cover through the shearing off of the upper-level cloud, consistent with observations. This study suggests that it is the ability of cold pools to lift thermodynamically favorable air that is critical for secondary convection of trade wind cumuli.

Journal

Journal of the Atmospheric Sciences – American Meteorological Society

Published: Jun 19, 2013

References

  • A comparison of cloud-resolving model simulations of trade wind cumulus with aircraft observations taken during RICO
    Abel
  • Effects of precipitation on the thermodynamic structure of the trade wind boundary layer
    Albrecht
  • Subcloud layer energetics of precipitating convection
    Barnes
  • A new parameterization for shallow cumulus convection and its application to marine subtropical cloud-topped boundary layers. Part I: Description and 1D results
    Bretherton