Showing papers by "Wilbert R. Skinner published in 2009"

Imaging of atmospheric gravity waves in the stratosphere and upper mesosphere using satellite and ground-based observations over Australia during the TWPICE campaign

Abstract: [1] During the Tropical Warm Pool International Cloud Experiment (TWPICE) an intense tropical low was situated between Darwin and Alice Springs, Australia. Observations made on 31 January 2006 by the Atmospheric Infrared Sounder instrument on the NASA Aqua satellite imaged the presence of atmospheric gravity waves (AGWs), at approximately 40 km altitude, with horizontal wavelengths between 200 and 400 km that were originating from the region of the storm. Airglow images obtained from Alice Springs (about 600 km from the center of the low) showed the presence of similar waves with observed periods of 1 to 2 h. The images also revealed the presence of 30- to 45-km-horizontal-wavelength AGWs with shorter observed periods of near 15 to 25 min. Ray tracing calculations show that (1) some of the long wavelength waves traveled on rays, without ducting, to the altitudes where the observations were obtained, and (2) shorter-period waves rapidly reached 85 km altitude at a horizontal distance close to the storm, thus occurring over Alice Springs only if they were trapped or ducted. The mesospheric inversion layer seen in the measured temperature data almost forms such a trapped region. The winds therefore critically control the formation of the trapped region. Wind profiles deduced from the available data show the plausibility for the formation of such a trapped region. Variations in the wind, however, would make ideal trapped region conditions short-lived, and this may account for the sporadic nature of the short-period wave observations.

Structure of the nonmigrating semidiurnal tide above Antarctica observed from the TIMED Doppler Interferometer

Abstract: [1] Spatial structure and temporal evolution of the nonmigrating semidiurnal tidal components over Antarctica are determined by analyzing horizontal wind measurements in the Mesosphere and Lower Thermosphere (MLT) collected using TIMED Doppler Interferometer (TIDI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite from 2002 to 2007. The data were organized into six specific intervals of approximately 60 days corresponding to the TIMED yaw periods. The results confirm the existence of a westward propagating zonal wave number 1 (W1) semidiurnal tidal component in the Antarctic MLT meridional wind field prior to the Austral summer solstice. This wave achieves a peak amplitude near 20 m s−1 at 90 km and is vertically stratified while extending latitudinally from the pole to 60°S. A similar structure is observed in the zonal wind field. However, the amplitude maximizes around the Austral summer solstice during the yaw period spanning 15 November to 15 January. In addition to a strong latitudinal gradient in amplitude, the W1 component also shows a vertical wavelength from 20 km near the pole to 40 km at 60°S. The amplitude and phase agree well with ground-based meteor radar observations from the South Pole. Evidence for significant though weaker standing (S0) and W3 components is also found. These components diminish in the vicinity of the pole and appear during the winter months with latitudinally restricted structures. The vertical wavelength of the S0 component during the summer is 25 km, similar to the W1 component. During the winter the wavelength of the S0 component becomes nearly evanescent.