American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 595466 bytes)

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D09S12, doi:10.1029/2004JD005097, 2005

Characteristics of instabilities in the mesopause region over Maui, Hawaii

Feng Li

Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Alan Z. Liu

Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Gary R. Swenson

Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Abstract

Characteristics of convective and dynamical instabilities in the mesopause region (between 85 and 100 km) over Maui, Hawaii (20.7°N, 156.3°W) are investigated using 19 nights, ∼133 hours of high-resolution wind and temperature data obtained by the University of Illinois Na wind/temperature lidar during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaigns. The mean probabilities of convective and dynamical instabilities are observed to be ∼3 and 10%, respectively, but there is considerable night-to-night variation. At any given time the probability that an unstable condition is found at some altitudes in the 85–100 km range is ∼90%. The Maui MALT data exhibit a distinct trend for N2 to increase with wind shear and vice versa. This correlation has important implications in the understanding of the development of instabilities. The night of 11 April 2002 is studied in detail in order to investigate the spatial and temporal structures of N2, wind shear, and convective and dynamical instabilities. A close linkage between instability and the mesosphere inversion layers (MILs) is identified. Most of the convectively and dynamically unstable regions are located above the MILs, with a tendency for dynamical instability to develop below convective instability. It is found that the vertical variations of N2 are often correlated with those of wind shear, but with a phase shift such that the maxima and minima of N2 are located ∼0.5–1 km below those of wind shear. Because of this shift, dynamical instability tends to develop in the region above the maximum wind shear, where relatively small N2 is observed to be associated with large wind shear. We also found that the wind shear is dominated by the contribution of the meridional wind, especially when the wind shear is strong. Possible mechanisms for the observed features are discussed.

Received 4 June 2004; accepted 8 December 2004; published 1 February 2005.

Keywords: instabilities; wind shear; mesopause.

Index Terms: 0310 Atmospheric Composition and Structure: Airglow and aurora; 3332 Atmospheric Processes: Mesospheric dynamics; 3384 Atmospheric Processes: Acoustic-gravity waves; 3389 Atmospheric Processes: Tides and planetary waves.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 595466 bytes)

Citation: Li, F., A. Z. Liu, and G. R. Swenson (2005), Characteristics of instabilities in the mesopause region over Maui, Hawaii, J. Geophys. Res., 110, D09S12, doi:10.1029/2004JD005097.