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 P1 rotational lines of OH depend on the choice of A values (T (Honl‐London, A) > T (Mies, A) > T (Espy, A)); (2) P =,213= 2072 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) × 108 cm−2 and (8.0 ± 0.8) × 108 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 k6 value for OH(υ′ = 0); (2) the higher k6 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(N2 and O2) 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.

Several notes on the OH* layer

“…(15) is proportional to the vibrationally dependent coefficient of Eq. (16), growing in the direction of the smaller v, as is well known from earlier results of modeling and measurements (e.g., Sivjee and Hamwey, 1987;Lopez-Moreno et al, 1987;McDade, 1991;Adler-Golden, 1997;Xu et al, 2012;Caridade et al, 2013).…”

Measurement of rotational temperature at Kolhapur, India

“…The OH(8-3) band was commonly used for hydroxyl temperature measurements in past years for high-and low-latitude regions (Agashe et al, 1977;Takahashi et al, 1974Takahashi et al, , 1999Takahashi and Batista, 1981;Myrabo, 1984;Sivjee and Hamwey, 1987). The hydroxyl airglow OH(8-3) band measurements have also been made in Antarctica (Stubbs et al, 1983;Williams, 1996).…”

Simultaneous measurement of OI 557.7 nm, O<sub>2</sub> (0, 1) Atmospheric Band and OH (6, 2) Meinel Band nightglow at Kolhapur (17° N), India

“…Sivjee and Hamwey, 1987, and references cited therin; Clemesha et al, 1990;Scheer and Reisin, 1990). Hence, OH and O 2 rotational temperatures can be assumed to represent the temperature around the mesopause heights of 87 (±4) and 94 (±3) km, respectively.…”

“…Due to the photodissociative action of the incoming solar ultraviolet radiation (on O 2 , O 3 , H 2 , H 2 O and CH 4 ) in the MLT region and the associated transport processes, this region hosts several active chemical species primarily grouped into two families, viz. the O x and HO x families (Smith, 2004;Brasseur and Solomon, 2005). The species of these two chemical families participate in numerous exothermic reactions that strongly depend upon the local density of atomic oxygen.…”