The Semidiurnal Atmospheric Tide at the Equinoxes: A Spectral Study with Mean-Wind-Related Influences and Improved Heating Rates

Abstract

Calculations of the semidiurnal atmospheric tide at the equinoxes using improved heating rates and realistic mean winds and temperatures are presented. The heating rates for equinox are quite similar to those reported by Forbes and Garrett (1978) and significantly different from those of Lindzen and Hong (1974). The basic conclusions of this study based on present heating rates are as follows: 1) Although effects of mean-wind-related (nonclassical) generation are clearly discernible, the improved agreement with observations of the present study over earlier classical studies with respect to wavelengths in the region 80?115 km is due primarily to the present heating rates rather than nonclassical effects; 2) with present heating rates there is no phase shift below 30 km as predicted by the earlier classical model; 3) without nonclassical effects the amplitude of the barometric tide is significantly underpredicted; 4) the solutions with nonclassical effects do not reproduce the rather large observed seasonal differences at the equinoxes; and 5) the sensitivity of resultant waves exhibiting substantial destructive interference to changes in the phases of the antisymmetric components may help to explain the large observed intermonthly and inter-annual variability in the meteor region.