Showing papers on "Winds aloft published in 1995"
TL;DR: The Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector as discussed by the authors.
Abstract: The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of approximately 100 m/s developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of approximately 150 m/s developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of approximately 0.08.
34 citations
TL;DR: In this article, the authors explored the dependence of the outflow from Coal Creek Canyon on surface cooling and channeling by winds above the canyon using three years of data from a portion of the network and found that the depth of the drainage flow and the height of the wind speed maximum were largest at external wind speeds near 3 m s−1.
Abstract: The atmospheric katabatic flow in the foothills of the Front Range of the Rocky Mountains has been monitored by a network of towers and sodars for several years as part of the ASCOT program. The dependence of the outflow from Coal Creek Canyon on surface cooling and channeling by winds above the canyon is explored by using three years of data from a portion of the network. The depth of the drainage flow and the height of the wind speed maximum were found to be largest at external wind speeds near 3 m s−1. For lighter winds aloft, the drainage depth, the height of the jet, and the drainage wind speed depend both on external wind speed and on the strength of the surface cooling. The magnitude of the near-surface temperature differences was also found to decrease with increasing surface cooling, possibly because of increasing turbulence caused by winds interacting with surface topography.
14 citations
TL;DR: In this paper, a best fit analysis in the least squares sense of the simultaneous measurements of the neutral winds to a 12-hour periodicity has provided amplitude and phase parameters for the semidiurnal tide as well as a measure of the mean wind.
Abstract: Fabry-Perot interferometer observations of the mesospheric hydroxyl emission and the lower thermospheric OI (5577A) emission have been conducted from an airglow observatory at a dark field site in southeastern Michigan for the past several years. The primary functions of the observatory are to provide a database for correlative observations with the UARS satellite and to provide a synoptic measurement program for the coupling energetics and dynamics of atmospheric regions effort, An intensive operational effort between May 1993 and July 1994 has resulted in a substantial data set from which neutral winds have been determined from the bifilter acquisition sequence. A 'best fit' analysis in the least squares sense of the simultaneous measurements of the neutral winds to a 12-hour periodicity has provided amplitude and phase parameters for the semidiurnal tide as well as a measure of the mean wind. The measured tidal amplitude is greater at the higher altitude, though the seasonal behavior at both altitudes is similar with greater amplitudes during August/September and April/May. Both meridional and zonal wind components are consistent with a semidiurnal tidal description during the entire observational sequence except for the May to July 1993 period. The mean winds show annual variation in the meridional flow, being equatorward from May to October and poleward during the winter. The zonal flow is primarily eastward during the entire observational window with higher speed flows during May/June at the higher attitude and June/July at the lower altitude. A comparison with a semidiurnal tidal model indicates that the measured tidal amplitudes are a factor of 2 times greater, while the phases show similar equinoctial transitions.
5 citations
TL;DR: In this paper, a fog episode characterized by quasi-periodic oscillations in visibility is described, and frequencies at which pressure and transparency fluctuate are compared, and the existence of intervals during which they are synchronized and the presence of strong winds aloft suggest that shear instabilities in the troposphere can influence the fog behaviour at ground.
Abstract: A fog episode characterized by quasi-periodic oscillations in visibility is described. Gravity waves are also present, and frequencies at which pressure and transparency fluctuate are compared. The existence of intervals during which they are synchronized and the presence of strong winds aloft suggest that shear instabilities in the troposphere can influence the fog behaviour at ground.
5 citations