Seasonal temperature variations in the mesopause region at mid-latitude: comparison of lidar and hydroxyl rotational temperatures using WINDII/UARS OH Height profiles

Fifty-one nights of lidar data and seventy-eight nights of Fourier transfor m spectrometer data taken during 1993 for the purpose of temperature measur ements in the mesopause region were analyzed. Observed OH*-temperatures fro m the (3-1) band over Delaware Observatory (43 degrees N) were compared sta tistically to (1) Na-layer temperatures, (2) temperatures at 87 km, and (3) OH*-temperatures inferred from the WINDII observed OH* height profiles and lidar observed temperature profiles, all over Fort Collins (41 degrees N). Seasonal temperature variations were deduced for two midlatitude sites and the resulting measurements were compared statistically. Very good agreemen t was obtained between the two sites in the magnitude of seasonal differenc es and variations. With marginal statistical significance, an overall 6-7 K difference between the observed and inferred seasonal averaged temperature s was detected. Other than the similar to 3 K difference in the summer acco untable by the latitude difference, the remaining discrepancy may be tentat ively resolved by a longitudinal difference with higher temperatures near m ountainous region, revealed From a comparison of temperatures observed at t he same nights over different Stations. Even with substantial data set cons idered here, geophysical variability still dominates the measurement uncert ainty in seasonal means. One useful conclusion of this study is that for ma ny purposes, the hydroxyl rotational temperature can be used as proxy for t he temperatures at 87+/-4 lint. (C) 1998 Elsevier Science Ltd. All rights r eserved.