Augmented Non‐LTE Parameterization of NO Infrared Radiative Cooling Rates

Abstract

AbstractParameterizations of NO cooling rates in thermospheric models have not changed substantially since the work of Kockarts (1980, https://doi.org/10.1029/GL007i002p0013). We investigate three areas to augment the standard parameterization. The first focuses on cooling‐rate contributions from the first NO “hot band.” Arguments concerning the difficulty or irrelevance of parameterizing hot‐band rates are addressed and either refuted or clarified. Parameterized hot‐band cooling peaks during periods of high solar activity, contributing up to 10%–15% additional cooling, in agreement with published line‐by‐line calculations. The second focuses on collisional NO‐O quenching rates. Recent theoretical calculations predict temperature‐dependent rates similar to those seen in collisional CO2‐O quenching rates. Yet available measurements of NO‐O quenching rates do not reveal clear temperature trends. Quenching rates parameterized with and without temperature dependence produce substantially different thermospheric cooling rates. Further research is needed to resolve these discrepancies. The third involves a linearization of parameterized NO cooling rates around a prescribed state, yielding thermal damping rates for use in parameterizations of subgrid‐scale dynamics. Thermal relaxation rates peak at up to 2 days−1 near 140 km, where they are competitive with corresponding rates due to viscous thermal conduction, consistent with the imputed role of NO in regulating thermospheric climate in response to extraterrestrial energy inputs.