Wavenumber spectra of horizontal wind and temperature measured with WINDII, Part I: observational results

The horizontal wind and temperature data inferred from the WINDII green lin e observations are used to derive global maps of vertical and horizontal wa venumber spectra, and to investigate the temporal/geographic variations of atmospheric wave motions. The planetary-scale disturbances between 90 and 1 20 km in September 1995 were found to be characterized by large r.m.s. velo cities of similar to 30-45 m/s and fractional temperatures of similar to 5- 9%, with maximum velocity variances in the region over the equatorial India n - Central Pacific Oceans. In contrast, the small-scale gravity waves disp layed mean fluctuation amplitudes of similar to 18-30 m/s and 3-6%, with th e maxima at mid-latitudes. The velocity variances of both scales slowly inc reased with increasing altitude at the lower heights, with a faster growth for the large-scale waves, but remained virtually constant above similar to 105 km due to the wave breaking and saturation. The results also revealed strong correlations between the longitudinal and temporal variations of the large- and small-scale waves. Vertical and horizontal wavenumber spectra o bserved at different locations and times showed great similarities, respect ively, confirming the notion of "universality". However, significant tempor al/geographic variations were found to exist, in respose to the changes in the wave source mechanisms and/or the interaction of gravity waves with, an d their filtering by, the variable environment. (C) 2000 Elsevier Science L td. All rights reserved.