SEMIDIURNAL AND DIURNAL TEMPERATURE TIDES (30-55 KM) - CLIMATOLOGY AND EFFECT ON UARS-LIDAR DATA COMPARISONS

Very good agreement is shown for diurnal and semidiurnal temperature v ariations calculated from lidar measurements in southern France and fr om data of the microwave limb sounder of the Upper Atmosphere Research Satellite (UARS). Tides induce temperature deviations observed in sou thern France to be as large as +/-3 K, with a maximum at the stratopau se. The amplitudes and phases of the semidiurnal variation change sign ificantly with season and location. Seasonal changes up to 2 K have be en clearly identified for the diurnal component. An analytic model of the diurnal component, based on sinusoidal functions, fits the data we ll, but is less successful for the semidiurnal component. Substantial agreement is also reported for the diurnal component between the resul ts of our analytical model and the published results of a two-dimensio nal global-scale wave model. In contrast, the semidiurnal component is in total disagreement with numerical simulations that report very sma ll amplitudes, as compared with the observations reported here. The co nfidence in detecting bias in data comparisons is improved if data use d are limited to periods from April to September and if time-of-day ad justments are applied. Comparison between lidar and nearly coincident UARS temperature measurements have revealed, systematically, for the 4 experiments aboard UARS, a significant residual mean difference of up to 3 K around 35-43 km. A comparison using simultaneous measurements suggests that the bias is associated with the variability of migrating tides and/or the presence of nonmigrating tides rather than instrumen tal characteristics.