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

摘要

Ground-based observations of OH(6, 2) Meinel band nightglow were carried out at Ranchi (23.3 degrees N, 85.3 degrees 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 (T-OH) with SABER/TIMED measurements in 30 cases was performed by defining almost coincident criterion of +/- 1.5 degrees latitude-longitude and +/- 3 min of the ground-based observations. Using SABER OH 1.6 and 2.0 mu m volume emission rate profiles as the weighing function, two sets of OH-equivalent temperature (T-1.6 and T-2.0 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.