OH Meinel band nightglow profiles from OSIRIS observations

Abstract

AbstractThe mesospheric nightglow spectrum is replete with OH Meinel band emissions, from the midvisible to the midinfrared. These emissions provide a wealth of aeronomic information, giving a physical view of the chemistry and dynamics of the upper atmosphere. The Optical Spectrograph and Infrared Imaging System (OSIRIS) instrument, on the Odin satellite, is currently one of the few satellite instruments that simultaneously observes emissions from multiple and separate Meinel bands. This has allowed the derivation of near‐global data sets of nighttime OH volume emission rate profiles for the Meinel (5‐1), (8‐3), and (9‐4) bands. The 2002–2013 climatologies consistently show that emission from bands in higher upper vibrational levels peaks at higher altitudes. The global average (5‐1), (8‐3), and (9‐4) band emission peak heights are at altitudes of 86.0 km, 86.7 km, and 87.1 km, respectively. The 1σ variation in the (5‐1), (8‐3), and (9‐4) band, peak heights are 1.8 km, 1.9 km, and 1.9 km, respectively. The climatological (30 day, 10° latitude) peak heights can vary significantly with both time and latitude; however, the (5‐1) band climatological peak height is nearly always below that of the (8‐3) band, which is nearly always below that of the (9‐4) band. The temporal variation in the emission peak height can have a significant impact on measurements of OH rotational temperatures from ground‐based observations of the OH layer. It was found that omitting the profile climatology can bias a ground‐based temperature measurement by as much as ±4 K and can also make ground‐based measurements susceptible to nonrealistic temperature variations.