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

摘要

Fifty-one nights of lidar data and seventy-eight nights of Fourier transform spectrometer data taken during 1993 for the purpose of temperature measurements in the mesopause region were analyzed. Observed OH~*-temperatures from the (3-1) band over Delaware Observatory (43°N) were compared statistically 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°N). Seasonal temperature variations were deduced for two midlatitude sites and the resulting measurements were compared statistically. Very good agreement was obtained between the two sites in the magnitude of seasonal differences and variations. With marginal statistical significance, an overall 6-7 K difference between the observed and inferred seasonal averaged temperatures was detected. Other than the ～ 3 K difference in the summer accountable by the latitude difference, the remaining discrepancy may be tentatively resolved by a longitudinal difference with higher temperatures near mountainous region, revealed from a comparison of temperatures observed at the same nights over different Stations. Even with substantial data set considered here, geophysical variability still dominates the measurement uncertainty in seasonal means. One useful conclusion of this study is that for many purposes, the hydroxyl rotational temperature can be used as proxy for the temperatures at 87 ± 4 km.