A comparison of ground-based hydroxyl airglow temperatures with SABER/TIMED measurements over 23 N, India

Abstract

Ground-based observations of OH(6, 2) Meinel band nightglow were carried out at Ranchi (23.3 N, 85.3 E), India, during January–March 2011, December 2011–May 2012 and December 2012–March 2013 using an all-sky imaging system. Near the mesopause, OH temperatures were derived from the OH(6, 2) Meinel band intensity information. A limited comparison of OH temperatures (TOH/ with SABER/TIMED measurements in 30 cases was performed by defining almost coincident criterion of 1.5 latitude–longitude and 3 min of the ground-based observations. Using SABER OH 1.6 and 2.0 μm volume emission rate profiles as the weighing function, two sets of OHequivalent temperature (T1:6 and T2:0 respectively) were estimated from its kinetic temperature profile for comparison with OH nightglow measurements. Overall, fair agreement existed between ground-based and SABER measurements in the majority of events within the limits of experimental errors. Overall, the mean value of OH-derived temperatures and SABER OH-equivalent temperatures were 197.3 4.6, 192.0 10.8 and 192.7 10.3 K, and the ground-based temperatures were 4–5K warmer than SABER values. A difference of 8K or more is noted between two measurements when the peak of the OH emission layer lies in the vicinity of large temperature inversions. A comparison of OH temperatures derived using different sets of Einstein transition probabilities and SABER measurements was also performed; however, OH temperatures derived using Langhoff et al. (1986) transition probabilities were found to compare well.