Dynamics of the middle atmosphere during CRISTA-2 as simulated by the National Center for Atmospheric Research thermosphere-ionospheremesosphere-electrodynamics general circulation model

Abstract

The National Center for Atmospheric Research (NCAR) thermosphere-ionospheremesosphere-electrodynamics general circulation model (TIME GCM) was run to study middle and upper atmospheric dynamics during the second flight of the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument on 7-16 August 1997. Strong quasi-stationary zonal wave number 1 and 2 signatures characterize the TIME GCM middle and high-latitude dynamics in the Southern Hemisphere. There is a migrating diurnal tide and a westward propagating wave number 2 nonmigrating diurnal tide at equatorial and low latitudes in both hemispheres. A westward propagating zonal wave number 1 quasi 5-day wave and a migrating semidiurnal tide are also evident in the TIME GCM mesopause region. We subsequently sample the TIME GCM results along the CRISTA orbital trajectory and process this subset of model data using the techniques invoked for the CRISTA data analyses. We compare these results with the full model analysis and find that the quasi-stationary wave 1 and wave 2 estimates are slightly affected by unresolved signatures of the semidiurnal tide and propagating planetary wave(s) in the middle and high-latitude Southern Hemisphere. The satellite sampling also results in a convolved migrating and nonmigrating diurnal tidal signature at low latitudes. We compare the TIME GCM sampled results with the CRISTA observations and find that the modeled stationary planetary waves are more confined to stratospheric high latitudes than the observed waves are, but there is more favorable model measurement agreement aloft. TIME GCM underestimates the diurnal tide that CRISTA observed throughout the middle atmosphere at equatorial and low middle latitudes.