Mesosphere and Lower Thermosphere Temperatures Simulated by WACCM-X With NAVGEM-HA Meteorological Analyses and Compared to SABER Observations

Realistic modeling of the dynamics and variability in the upper mesosphere and lower thermosphere (UMLT) is critical to understand the coupling between different layers of the whole atmosphere system. Here we present simulations of the UMLT temperatures at similar to 100 km altitude for one year during 2014 by the Whole Atmosphere Community Climate Model with thermosphere-ionosphere extension (WACCM-X) constrained below similar to 90 km using meteorological analysis products of the high-altitude version of Navy Global Environmental Model (NAVGEM-HA). The model results are sampled at the same times and latitudes and longitudes as the satellite observations from Thermosphere Ionosphere and Mesosphere Electric Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER). Comparisons show that the observed and modeled daily zonal mean temperatures are correlated (r similar to 0.5-0.7) at most latitudes between +/- 50 degrees. Both the observations and simulations show an annual variation at mid-latitudes in two hemispheres with the temperature maximum in summer and the minimum in winter, and at lower latitudes the semiannual variation becomes stronger having the temperature maximums at equinoxes and the minimums during solstices. However, the temperatures observed are on average similar to 5-10 K (3%-5%) smaller than the model and the observations show a larger variability. Moreover, migrating tidal amplitudes are mostly overestimated by the model. Though differences are noticed, the WACCM-X simulations with NAVGEM-HA meteorological analyses are overall consistent with the SABER observations. These results support that whole atmosphere models informed by high altitude observations would help to simulate the UMLT variability and the atmosphere and ionosphere coupling. The upper mesosphere and lower thermosphere (UMLT) is the region from similar to 80 to similar to 110 km, which is subject to influences from below by the lower atmosphere. Yet, the dramatically large variability exhibited in the UMLT region has not been fully explained. High Altitude (HA) meteorological analysis products of the Navy Global Environmental Model (NAVGEM) that incorporate observations in the lower and middle atmospheres have been demonstrated to provide a more realistic description of the upper atmosphere state. For this study, the NAVGEM-HA meteorological analyses from the surface to similar to 90 km altitude are used to inform the Whole Atmosphere Community Climate Model with thermosphere-ionosphere extension (WACCM-X). We evaluate the WACCM-X model results of the UMLT temperatures at similar to 100 km altitude for one year during 2014 by comparing with the observations from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) operated on the Thermosphere Ionosphere and Mesosphere Electric Dynamics (TIMED) spacecraft. The study finds that though there are some differences the WACCM-X simulations overall agree with the SABER observations and the model captures the observed annual and semiannual variations. Assimilation in whole atmosphere models would be useful to better represent and interpret the dramatic variability of the UMLT region. Whole atmosphere model simulations with meteorological analyses are overall consistent with the satellite observations at similar to 100 km altitude Temperatures observed are on average similar to 5-10 K (3%-5%) smaller than the model, and the observations exhibit a larger variability Annual and semiannual variations and migrating tidal amplitudes are not fully represented in the model