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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D03S90, doi:10.1029/2004JD004954, 2005

Climatology of short-period gravity waves observed over northern Australia during the Darwin Area Wave Experiment (DAWEX) and their dominant source regions

P.-D. Pautet

Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah, USA


M. J. Taylor

Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah, USA


A. Z. Liu

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


G. R. Swenson

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


Abstract

The Darwin Area Wave Experiment (DAWEX) was designed to investigate the generation and propagation of gravity waves from intense regions of localized convection that occur regularly over northern Australia (in the vicinity of Darwin) during the premonsoon period. This multinational program was conducted during the austral spring 2001 using a range of coordinated optical, radar, and in situ balloon measurements. As part of this program, all-sky image observations of short-period gravity wave events in the near infrared OH nightglow emission (altitude ∼87 km) were made from two well-separated sites in northern Australia: Wyndham (15.5°S, 128.1°E) and Katherine (14.5°S, 132.3°E), over a 10-day period during November 2001. A total of 25 extensive wave events were observed during this period, from which the dominant horizontal wave characteristics were determined to be: wavelength 25–35 km and observed phase speed 27–75 m/s, yielding observed periods from 7 to 14 min, consistent with previous measurements at other low-latitude sites. A key finding of this study was a marked anisotropy in the wave propagation headings, with over 3/4 of the events exhibiting a strong southward component of motion and a clear preference for wave progression over the azimuthal range SE to SSW. Although this range encompasses gravity waves originating locally from the Darwin area, the majority of the wave events exhibited propagation headings consistent with more distant sources located to the north and northwest of Australia. Assuming deep convection was the dominant mechanism for the waves, the strong asymmetry in their velocity distribution appears to result from a combination of nonuniformity in the geographic occurrence of thunderstorms coupled together with significant wind filtering effects at the source altitude and within the middle atmosphere. These results are consistent with long-range, short-period wave propagation (most probably in the form of ducted waves) possibly from intense convective regions located ∼1000 km to the north over the Indonesian Island chain.

Received 26 April 2004; accepted 15 December 2004; published 11 February 2005.

Keywords: DAWEX campaign; gravity waves; convective sources.

Index Terms: 3334 Atmospheric Processes: Middle atmosphere dynamics (0341, 0342); 0310 Atmospheric Composition and Structure: Airglow and aurora; 3314 Atmospheric Processes: Convective processes; 3332 Atmospheric Processes: Mesospheric dynamics; 3384 Atmospheric Processes: Acoustic-gravity waves.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 532432 bytes)

Citation: Pautet, P.-D., M. J. Taylor, A. Z. Liu, and G. R. Swenson (2005), Climatology of short-period gravity waves observed over northern Australia during the Darwin Area Wave Experiment (DAWEX) and their dominant source regions, J. Geophys. Res., 110, D03S90, doi:10.1029/2004JD004954.