TIDAL INFLUENCE ON MIDLATITUDE AIRGLOW - COMPARISON OF SATELLITE AND GROUND-BASED OBSERVATIONS WITH TIME-GCM PREDICTIONS

WINDII, the Wind imaging interferometer on the Upper Atmosphere Resear ch Satellite measures winds and emission rates from selected excited m etastable species. Measurements of the 558-nm emission from atomic oxy gen provide both the wind from the Doppler shift, and the atomic oxyge n concentration from the emission rate. Thus the tides and their influ ence on atomic oxygen are measured with the same instrument. Ground-ba sed airglow measurements provide vertical integrals of the same quanti ties and coordinated observations were obtained between WINDII and gro und-based instruments at Bear Lake (42.5 degrees N, 212 degrees E) for O(S-1) 558 nm winds and O-2(b(1)Sigma) (0,1) band emission rate and t emperature. The TIME-GCM model has recently incorporated airglow photo chemistry, so that direct comparisons may be made with airglow observa tions, without inverting those observations to atomic oxygen distribut ions. In this study, the influence of tides on airglow emission at mid latitude is studied through the comparison of the above data sets with the TIME-GCM model, extending earlier studies conducted for the equat orial region. At the vernal equinox the upward propagating diurnal tid e is found to be the dominant influence on airglow diurnal variation. At solstice the diurnal tide does not penetrate to as high an altitude , so that the dominant influence is then the in situ semidiurnal tide. This conclusion is consistent with both WINDII observations and TIME- GCM predictions, whose data sets agree extremely well with one another . The ground-based results agree well in the local time variation patt ern, but the amplitudes observed are larger than for WINDII or the TIM E-GCM by roughly a factor of 2. This difference illustrates very clear ly the differences between a tidal pattern observed at a single site f ora few nights, and a global pattern that is first zonally averaged, a nd then combined in local time over about 1 month, as is done with the WINDII data. The agreement of these averaged data with the TIME-GCM m odel strongly suggests that they accurately represent the behavior of the zonally averaged atmosphere.