Sensitivity of gravity wave fluxes to interannual variations in tropical convection and zonal wind

Sensitivity of gravity wave fluxes to interannual variations in tropical convection and zonal wind AbstractUsing an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, we examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Niño and a La Niña year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. We compare modeled monthly-mean regional variations in wind and temperature with reanalyses, and we validate the modeled gravity waves using satellite- and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitaiton, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models due to deficiencies in parameterizations of gravity wave intermittency. Our results suggest a way forward to improve model representations of lowermost stratospheric quasi-biennial oscillation winds and teleconnections. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

Sensitivity of gravity wave fluxes to interannual variations in tropical convection and zonal wind

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0469
D.O.I.
10.1175/JAS-D-17-0044.1
Publisher site
See Article on Publisher Site

Abstract

AbstractUsing an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, we examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Niño and a La Niña year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. We compare modeled monthly-mean regional variations in wind and temperature with reanalyses, and we validate the modeled gravity waves using satellite- and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitaiton, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models due to deficiencies in parameterizations of gravity wave intermittency. Our results suggest a way forward to improve model representations of lowermost stratospheric quasi-biennial oscillation winds and teleconnections.

Journal

Journal of the Atmospheric SciencesAmerican Meteorological Society

Published: Jun 21, 2017

References

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