Temperature and chemistry of the polar mesopause OH

Abstract

Intensities ( I ) and rotational temperatures ( T ) of the OH(8, 3) and (6, 2) bands were derived from spectrophotometric observations of airglow emissions, over Longyearbyen in Spitsbergen, made in December 1984. The high latitude of the Spitsbergen Observatory (78°15′N) permitted 24‐hour coverage of the wintertime polar airglow. These measurements yielded the following results: (1) T derived from P 1 rotational lines of OH depend on the choice of A values ( T (Honl‐London, A ) > T (Mies, A ) > T (Espy, A )); (2) P =,213 = 207 2 K 207 implying a 3‐ to 5‐K/km temperature gradient in the atmosphere around 85 km height; (3) Ī(8, 3) = 314 ± 30 R and Ī (6, 2) = 1025 ± 110 R; the corresponding OH(υ′) columnar abundances are (5.5 ± 0.6) × 10 8 cm −2 and (8.0 ± 0.8) × 10 8 cm −2 for υ′ = 8 and υ′ = 6 vibrational levels. These results are compared with the predictions of a one‐dimensional oxygen‐hydrogen model which shows that (1) the reaction rate of OH H + O 2 may be much higher than the laboratory‐measured k 6 value for OH(υ′ = 0); (2) the higher k 6 value accounts for the separation of OH layers for different υ′ levels observed in various rocket measurements of OH * (υ′) profiles and implies a positive temperature gradient in the atmosphere around 85 km; (3) Llewellyn et al.’s (1978) rate for quenching of OH * by M(N 2 and O 2 ) is required in the model to match the calculated column abundance of OH * in υ′ = 8 to the value derived from the observed intensities of the airglow OH(8, 3) band; and (4) a perhydroxyl source must be invoked for the model to yield a column abundance of OH * in υ′ = 6 consistent with the intensity of the airglow OH(6, 2) band observed in Spitsbergen.