Mesospheric temperatures from observations of the hydroxyl (6-2) emission above Davis, Antarctica: A comparison of rotational and Doppler measurements

We present observations of the hydroxyl (6-2) airglow lines from similar to 87 km altitude obtained at Davis station, Antarctica, in the austral winte r of 1999. Nine nights of observations were made of the P-branch near lambd a 840 nm with a Czerny-Turner scanning spectrometer (CTS); at the same time , high-resolution Fabry-Perot Spectrometer (FPS) spectra were collected of the Q(1)(1) doublet at lambda 834 nm. Rotational temperatures were determin ed from the CTS observations, while Doppler temperatures were derived from the line-widths of the FPS Q1(1) spectra. Absolute temperatures determined by these methods are uncertain by similar to2 and similar to 20 K, respecti vely. For the comparison we set the value of the reflective finesse of the FPS at lambda 834 nn so the mean FPS temperature from one night of simultan eous data was equal to that from the CTS, and then looked at the measured v ariations in each data set for the other eight nights. Both instruments sho w the upper mesosphere temperature to vary in a similar manner to within th e observational errors of the measurements, implying an equivalence of the rotational and Doppler temperatures. We believe that this is the first publ ished simultaneous, same-site, comparison of rotational and Doppler tempera tures from the OH emission.