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

Abstract

A data assimilation system (DAS) is described for global atmospheric reanalysis from 0- to 100-km altitude. We apply it 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 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 105 observations of the mesosphere and lower thermosphere (MLT) every 6 h. While all MLT reanalyses show skill relative to independent wind and temperature measurements, HYBRID outperforms 4DVAR. MLT fields at 1-h resolution (6-h analysis and 1–5-h forecasts) outperform 6-h analysis alone due to a migrating semidiurnal (SW2) tide that dominates MLT dynamics and is temporally aliased in 6-h time series. MLT reanalyses reproduce observed SW2 winds and temperatures, including phase structures and 10–15-day amplitude vacillations. The 0–100-km reanalyses reveal quasi-stationary planetary waves splitting the stratopause jet in July over New Zealand, decaying from 50 to 80 km then reintensifying above 80 km, most likely via MLT forcing due to zonal asymmetries in stratospheric gravity wave filtering.

Large‐Amplitude Mountain Waves in the Mesosphere Accompanying Weak Cross‐Mountain Flow During DEEPWAVE Research Flight RF22

“…Zonal and meridional winds measured by the meteor radar at Kingston, Tasmania, and obtained from the NAVGEM T119L74 reanalysis (Eckermann et al, ) from 03 to 09 UT on 13 July centered on Lauder are shown in Figures b and c. The differences between the radar and reanalysis winds above ~80 km likely reflect the 23° of longitude and 2° of latitude separation between the two sites, as well as the inference of a large semidiurnal tide at these latitudes on 13 July measured by the meteor radar and implied by NAVGEM reanalysis.…”

Local and Remote Planetary Wave Effects on Polar Mesospheric Clouds in the Northern Hemisphere in 2014

“…These observations came from bias‐corrected Version 4.2 MLS temperatures, Version 2.0 temperature retrievals from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on NASA's TIMED satellite, and O 2 microwave radiances from the Special Sensor Microwave Imager/Sounder (SSMIS) on three separate satellites (F17, F18, and F19) of the Defense Meteorological Satellite Program. The fields used here correspond to a reanalysis run using hybrid ensemble/4DVAR (four‐dimensional variational) data assimilation at a T119L74 outer‐loop (T47L74 inner‐loop) resolution (see Eckermann et al, , for details). For the present work, these reanalyses were reinterpolated onto a pressure grid with a constant pressure‐height resolution of 1 km, and from the quadratic Gaussian grid onto a regular 1° × 1° global grid.…”

Momentum Flux Spectra of a Mountain Wave Event Over New Zealand

“…The calculated T ′ from mixing ratio contours for each pass are shown in Figure . The background d / dz used in equation was obtained from NAVGEM reanalysis (Eckermann et al, ), reinterpolated onto a constant geometric height grid for the 13 July 2014 flight. The temperature profile was the average of all reanalysis grid points within a circular region centered near Mt.…”