Response of OH airglow temperatures to neutral air dynamics at 78°N, 16°E during the anomalous 2003–2004 winter

Abstract

Hydroxyl (OH) brightness temperatures from the mesopause region derived from temperature profiles from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite are compared with OH(6‐2) rotational temperatures measured by spectrometer from Longyearbyen, Norway (78°N, 16°E), during the winter 2003–2004. The two series correspond well, although the satellite measurements are higher by an average of 5.6 K ± 4.4 K. Reasons for this apparent bias are discussed. The two series give a near‐continuous temperature record from this winter, making it possible to study the response of the temperatures to neutral air dynamics observed from meteor radar measurements of meridional and zonal wind. Vertical profiles of 1.6 μm OH volume emission rates from SABER reveal that the unusually high temperatures observed during January and February 2004 (240–250 K) correspond to a very low and bright OH layer. Significant linear correlations are found between meridional wind, OH temperature, and peak altitude. These data support the theory that the high temperatures result from an anomalously strong upper stratospheric vortex that confined air to the polar regions, coupled with meridional transport, which led to a strong downwelling of atomic oxygen‐rich air, thereby lowering the altitude of the OH layer. The SABER data reveal that the re‐formation of the OH layer at approximately 78 km altitude accounted for an increase in temperature of approximately 15 K, while the remaining temperature increase (20–35 K) is attributed to adiabatic heating and chemical heating from the exothermic reactions involved in producing the vibrationally excited OH.