Study of rotational temperatures with a multi-wavelength photometer from the Indian equatorial station Tirunelveli

Abstract

A multi-wavelength photometer (MWP) was operated at the equatorial station Tirunelveli (8.7°N, 77.8°E geographic), India, to study different nightglow emissions. In the present work, the intensities of the P1(2) and P1(4) lines of the OH(6,2) Meinel band were used to derive rotational temperatures in the mesosphere-lower thermosphere (MLT) region during February–April 2015. The methodology adopted to derive rotational temperatures using the MWP data is discussed in detail. A comparison with temperatures measured by the Sounding of the Atmosphere by Broadband Emission Radiometry (SABER) instrument onboard NASA's TIMED satellite was performed to validate the MWP-derived rotational temperatures. An excellent correlation was observed between the MWP-derived and SABER temperatures, with a mean temperature difference of ∼15 K. The plausible reasons for this temperature bias are discussed in this work. In addition, the P1 line intensities of the OH(6,2) band and temperatures obtained with the MWP were compared with the OH broadband intensity acquired by a co-located all-sky airglow imager (ASAI). Furthermore, the local time variation of the MWP-derived temperatures was studied, and the results were compared with the NRLMSISE-00 model simulation. This study demonstrates the effectiveness of the MWP in measuring MLT temperatures and highlights the importance of multi-instrument comparisons for validating the temperatures and airglow intensity.