Mesospheric energy loss rates by OH and O₂ emissions at 23^°S

Abstract. The nightglow OH(9, 4) and O₂ atmospheric (0,1) band emission intensities and their rotational temperatures T(OH) and T(O₂), respectively, observed at Cachoeira Paulista (23^°S, 45^°W), Brazil, during the period from October 1989 to December 1990, have been analyzed to study the nighttime mesospheric energy loss rates through the radiations from the vibrationally excited OH^* and electronically excited O₂^* bands. The total emission rates of the OH Meinel bands, O₂ atmospheric (0,0) and O₂ infrared atmospheric (¹Δ_g) bands were calculated using reported data for the relative band intensities I_(ν^'',ν^')/I_(9,4), I_O2A(0,0)/I_O2A(0,1) and I_O2(¹Δ_g)/I_O2A(0,1). It was found that there is a minimum in equivalent energy loss rate by the OH^* Meinel bands during December/January (equivalent energy loss rate of 0.39K/day^*, where day^* means averaged over the night) and maximum in equivalent energy loss rate during September (equivalent energy loss rate of 0.98K/day^*). Energy loss rate by the O₂^* radiation, on the other hand, is weaker than that by the OH^* Meinel bands, showing equivalent energy loss rates of 0.12K/day^* and 0.22K/day^* during January and September, respectively.