Thermospheric Nitric Oxide Density From SABER: Local Time Dependence and Validation Against Independent Observations

Abstract The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) nitric oxide (NO) concentration is a newly derived data set from SABER NO emission rate measurements, covering altitudes from 120 to ∼250 km with full local time coverage. The Naval Research Laboratory Mass Spectrometer Incoherent Scatter radar (NRLMSIS ® ) 2.1 is a semi‐empirical model of atmospheric temperature and density, which provides NO number density from ∼73 km to the exobase based on observations from six space‐based instruments. In this work, we evaluate the SABER NO density against MSIS 2.1 NO and other satellite data sets assimilated in MSIS 2.1, through a comprehensive analysis of altitude, local time, latitude, season, solar, and geomagnetic activity dependencies. The SABER NO is mostly in good agreement with MSIS 2.1 and the other NO data sets. SABER NO exhibits strong local time variations that have a diurnal component at all altitudes and an additional semidiurnal component at 120–130 km at low latitudes. These local time variations are not represented in MSIS 2.1 NO, the local time variation of which is driven solely via coupling with the MSIS temperature. Assimilating SABER NO between 120 and 130 km into MSIS significantly improves the model's local time dependence at all altitudes. These results demonstrate SABER's utility as an extensive source of information on upper atmospheric NO, providing critical insight for future modeling and climatological applications.