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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D02S04, doi:10.1029/2002JD003067, 2004

Observations of overturning in the upper mesosphere and lower thermosphere

M. F. Larsen

Department of Physics, Clemson University, Clemson, South Carolina, USA


A. Z. Liu

Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois, USA


C. S. Gardner

Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois, USA


M. C. Kelley

School of Electrical Engineering, Cornell University, Ithaca, New York, USA


S. Collins

School of Electrical Engineering, Cornell University, Ithaca, New York, USA


J. Friedman

Arecibo Observatory, Arecibo, Puerto Rico


J. H. Hecht

Space and Environmental Technology Center, The Aerospace Corporation, Los Angeles, California, USA


Abstract

A number of observations of the sodium density primarily in the mesosphere and lower thermosphere (but also of the electron density structure) have shown what appears to be overturning or convective roll cells near the transition from the mesosphere to the lower thermosphere. The cells are found in the region between 95 and 105 km and occur near the boundary between the region of lower stability in the mesosphere and the region of higher stability in the lower thermosphere. The vertical scale for the rolls is ∼5–6 km, and the timescale is ∼1–3 hours. The rolls occur in a region characterized by large shear in the neutral winds, but the timescales are too long to be explained by simple Kelvin-Helmholtz instability. We present observations from the University of Illinois lidar facility located at the Starfire Optical Range near Albuquerque, New Mexico, from the Arecibo Observatory in Puerto Rico, and from the Maui/MALT Lidar Facility located on Maui in Hawaii that show the overturning structure. possible mechanisms for generating the convective rolls are discussed, Including the relationship of the observed features to the characteristics expected for an inflection point instability.

Received 22 October 2002; accepted 15 October 2003; published 22 January 2004.

Index Terms: 0341 Atmospheric Composition and Structure: Middle atmosphere—constituent transport and chemistry (3334); 0350 Atmospheric Composition and Structure: Pressure, density, and temperature; 0355 Atmospheric Composition and Structure: Thermosphere—composition and chemistry.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 709764 bytes)

Citation: Larsen, M. F., A. Z. Liu, C. S. Gardner, M. C. Kelley, S. Collins, J. Friedman, and J. H. Hecht (2004), Observations of overturning in the upper mesosphere and lower thermosphere, J. Geophys. Res., 109, D02S04, doi:10.1029/2002JD003067.