Occurrence Frequency of Convective Gravity Waves during the North American Thunderstorm Season

Hoffmann, L.; Alexander, M.J.

doi:10.1029/2010JD014401

Journal Article

PreJuSER-9730

Occurrence Frequency of Convective Gravity Waves during the North American Thunderstorm Season

Hoffmann, L.FZJ* ; Alexander, M. J.

2010
Union Washington, DC

Journal of Geophysical Research 115, (2010) [10.1029/2010JD014401]

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Please use a persistent id in citations: http://hdl.handle.net/2128/20451 doi:10.1029/2010JD014401

Abstract: Convective gravity waves are an important driver of the equator-to-pole circulation in the stratospheric summer hemisphere, but their nature is not well known. Previous studies showing tight relationships between deep convection and convective waves mainly focus on tropical latitudes. For midlatitudes most analyses are based on case studies. Here we present a new multiyear occurrence frequency analysis of convective waves at midlatitudes. The study is based on radiance measurements made by the Atmospheric Infrared Sounder (AIRS) satellite experiment during the North American thunderstorm season, May to August, in the years 2003-2008. For this study we optimized an existing algorithm to detect deep convection in AIRS data to be applicable at midlatitudes. We also present a new detection algorithm for gravity waves in AIRS data based on a variance filter approach for 4.3 mu m brightness temperatures. The new algorithm can detect plane wave perturbations in the altitude range from 20 to 65 km with vertical wavelengths larger than 15 km and horizontal wavelengths from 50 to 1000 km. By analyzing spatial and temporal correlations of the individual AIRS observations, it can be shown that more than 95% of the observed gravity waves in a core region over the North American Great Plains are related to deep convective clouds, i.e., are likely being classified appropriately as convective waves. We conclude that the core region is a good location to observe and characterize the properties of convective waves at midlatitudes. The statistical analyses presented here are also valuable to validate parameterization schemes for convective gravity waves. For completeness, it should be mentioned that our analyses cover not only the U. S. Midwest but the North American continent as well as the surrounding ocean regions in general. Our analysis also reveals interesting details about tropical convection and related gravity wave activity, as well as the capability of the AIRS instrument to observe these.

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Meteorology & Atmospheric Sciences

Note: Support for this work was provided by the NASA program Earth System Science Research using Data and Products from TERRA, AQUA, and ACRIM Satellites, contract NNH06ZDA001N 06-EOS/06-0203 and NSF Physical and Dynamical Meteorology Program 0632378. We thank Manfred Ern and Peter Preusse, both at Forschungszentrum Julich, Germany, for suggestions and comments related to this study. We thank Duy-Viet Do, Forschungszentrum Julich, Germany, for technical support.

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