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- Author or Editor: Allan I. Carswell x
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Abstract
During February and March 1993, Rayleigh lidar observations of temperature structure and gravity wave activity were carried out in the high Canadian Arctic at Eureka, Northwest Territories (80°N, 86°W). A sudden warming was observed first in the upper stratosphere during late February and then at lower levels in early March. The warming appeared to be part of a disturbance of the entire middle atmosphere with temperature changes in the mesosphere and lower stratosphere being opposite in sign to those in the upper stratosphere. Shorter time and length scale temperature fluctuations, observed in the upper stratosphere, are interpreted as being a result of atmospheric gravity waves. The wave amplitudes are shown to be capable of inducing convective instability. The rms perturbation and available potential energy density show substantial vertical and day-to-day variability in regions of conservative and dissipative growth rates. Vertical growth of the potential energy spectral density is seen to cease at the broadband convective instability saturated limit. There appeared to be substantially greater dissipation of gravity wave energy within the upper-stratospheric warming in comparison with the preceding and following periods.
Abstract
During February and March 1993, Rayleigh lidar observations of temperature structure and gravity wave activity were carried out in the high Canadian Arctic at Eureka, Northwest Territories (80°N, 86°W). A sudden warming was observed first in the upper stratosphere during late February and then at lower levels in early March. The warming appeared to be part of a disturbance of the entire middle atmosphere with temperature changes in the mesosphere and lower stratosphere being opposite in sign to those in the upper stratosphere. Shorter time and length scale temperature fluctuations, observed in the upper stratosphere, are interpreted as being a result of atmospheric gravity waves. The wave amplitudes are shown to be capable of inducing convective instability. The rms perturbation and available potential energy density show substantial vertical and day-to-day variability in regions of conservative and dissipative growth rates. Vertical growth of the potential energy spectral density is seen to cease at the broadband convective instability saturated limit. There appeared to be substantially greater dissipation of gravity wave energy within the upper-stratospheric warming in comparison with the preceding and following periods.
Abstract
This paper describes wind measurements derived from displacements of small-scale cloud features obtained from time-lapse videography and simultaneous lidar measurements. Lidar provides the attitude of the cloud feature, with a high degree of accuracy. The video picture provides the information on the horizontal displacement coordinates of the wind speed and direction. Analysis of a large body of data has shown that the method can provide wind information with good spatial and temporal resolution. Comparisons with rawinsonde measurements show very good agreement.
Abstract
This paper describes wind measurements derived from displacements of small-scale cloud features obtained from time-lapse videography and simultaneous lidar measurements. Lidar provides the attitude of the cloud feature, with a high degree of accuracy. The video picture provides the information on the horizontal displacement coordinates of the wind speed and direction. Analysis of a large body of data has shown that the method can provide wind information with good spatial and temporal resolution. Comparisons with rawinsonde measurements show very good agreement.
Abstract
Four hundred and twenty-two nights of stratospheric gravity wave observations were obtained with a Rayleigh lidar in the High Arctic at Eureka (80°N, 86°W) during six wintertime measurement campaigns between 1992/93 and 1997/98. The measurements are grouped in positions relative to the arctic stratospheric vortex for comparison. Low gravity wave activity is found in the vortex core, outside of the vortex altogether, and in the vortex jet before mid-December. High gravity wave activity is only found in the vortex jet after late December, and is related to strengthening of the jet and decreased critical-level filtering. Calculations suggest that the drag induced by the late-December gravity wave energy increases drives a warming already observed in the vortex core, thereby reducing vortex-jet wind speeds. The gravity waves provide a feedback mechanism that regulates the strength of the arctic stratospheric vortex.
Abstract
Four hundred and twenty-two nights of stratospheric gravity wave observations were obtained with a Rayleigh lidar in the High Arctic at Eureka (80°N, 86°W) during six wintertime measurement campaigns between 1992/93 and 1997/98. The measurements are grouped in positions relative to the arctic stratospheric vortex for comparison. Low gravity wave activity is found in the vortex core, outside of the vortex altogether, and in the vortex jet before mid-December. High gravity wave activity is only found in the vortex jet after late December, and is related to strengthening of the jet and decreased critical-level filtering. Calculations suggest that the drag induced by the late-December gravity wave energy increases drives a warming already observed in the vortex core, thereby reducing vortex-jet wind speeds. The gravity waves provide a feedback mechanism that regulates the strength of the arctic stratospheric vortex.
