Rotational temperatures retrival from the Arecibo Observatory Ebert-Fastie spectrometer and their inter-comparison with Lidar and SABER measurements

Abstract

Rotational temperatures in the Mesosphere-Lower Thermosphere region are estimated by utilizing the OH(6,2) Meinel band nightglow emission observed with an Ebert-Fastie Spectrometer (EFS) operated at Arecibo Observatory (AO), Puerto Rico (18.35 o N, 66.75 o W) during February-April 2005. To validate the estimated rotational temperatures, a comparison with temperatures obtained from a co-located Potassium Temperature Lidar (K-Lidar) and overhead passes of the Sounding of the Atmosphere by Broadband Emission Radiometry (SABER) instrument onboard NASA's TIMED satellite are performed. Two types of weighting functions are applied on the K-Lidar temperatures to compare them with EFS temperatures. The first type has a fixed peak altitude and a fixed full width at half maximum (FWHM) for the whole night. In the second type, the peak altitude and FWHM vary with the local time. Average temperature difference between the EFS and K-Lidar obtained with both types of weighting functions are comparable with the previously published results from different latitude-longitude sectors. Further, it is found that temperature comparison improves when the time varying weighting functions are considered. On the other hand, we have shown that comparison of temperatures obtained from these two instruments could provide a better estimate of the OH(6,2) peak altitudes if a reference temporal trend of the OH(6,2) peak altitudes is available. Also, it is noticed that there are significant differences between the seasonal mean OH(6,2) peak altitudes obtained from SABER observation and model calculation. Such a detailed study using the AO EFS data has not previously been carried out.