A Comparison Study of NO Cooling Between TIMED/SABER Measurements and TIEGCM Simulations

We investigate the latitudinal and longitudinal variations of thermospheric nitric oxide (NO) cooling rate from 2005 to 2016. We compare the maximum of the NO cooling rate and its altitude from measurements by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on National Aeronautics and Space Administration (NASA)'s TIMED (Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics) satellite and from simulations by the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). In both data and model, the maximum NO cooling rate varies with ~11-year solar cycle, while the altitude of the peak value does not. At local noon, the maximum NO cooling rate from TIEGCM is significantly larger than that derived from SABER, especially in solar minimum. There are differences in the altitudes of the maximum NO cooling rates between the observations and simulations. The largest difference occurs at noon at low latitudes, with SABER values exceeding TIEGCM values by more than 10 km with a maximum difference of 16 km near solar maximum. Model sensitivity tests suggest that the biases are caused by a model temperature overestimation in the low thermosphere, and tides in the TIEGCM lower boundary play an important role in inducing the low-latitude temperature overestimation by the model. In addition, SABER's height-integrated cooling rate (NO flux) exceeds that from TIEGCM, primarily due to the lower cooling rates at 140–200 km in the model.