High-Altitude (0-100km) Global Atmospheric Reanalysis System: Description and Application to the 2014 Austral Winter of the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

We outline salient details of a data assimilation system (DAS) designed for global atmospheric reanalysis from 0-100 km altitude, based around the Navy Global Environmental Model (NAVGEM). We apply this system to the 2014 austral winter of the Deep Propagating Gravity Wave Experiment (DEEPWAVE), an international field campaign focused on gravity wave dynamics from 0 to 100 km, where an absence of meteorological reanalysis above 60 km inhibits research. Four experiments were performed from April to September 2014 and assessed for reanalysis skill above 50 km. A four-dimensional variational (4DVAR) run specified initial background error covariances statically. A hybrid-4DVAR (HYBRID) run formed background error covariances from an 80-member forecast ensemble blended with a static estimate. Each configuration was run at low and high horizontal resolution. In addition to operational observations below 50 km, each experiment assimilated around 10⁵ observations of the mesosphere and lower thermosphere (MLT) every 6 h. We describe relevant findings from these experiments focused on the MLT reanalysis, including MLT reanalysis skill relative to independent wind and temperature measurements, migrating semidiurnal (SW2) tides and planetary waves captured in the reanalysis, and flow-based MLT error covariances formed from the 80-member forecast ensembles. Future directions for this system are discussed, including planned 0-100 km reanalysis support for NASA's Atmospheric Waves Experiment (AWE).