Migrating thermospheric tides

Abstract

Abstract. The capabilities of the global-scale wave model (GSWM) [Hagan et al., 1995] are extended to include migrating thermospheric solar tides. The GSWM thermospheric tidal forcing parameterization is based on neutral gas heating calculated from first principles in the National Center for Atmospheric Research (NCAR) thermosphere/ionosphere electrodynamics general circulation model (TIE-GCM). This is the first time that a physics-based thermospheric forcing scheme has been used in a model like G SWM. Previous two-dimensional steady state linear tidal models used exospheric temperature measurements to calibrate upper atmospheric tidal forcing. New GSWM results illustrate thermospheric tidal responses that are largely consistent with tides in the TIE-GCM. Diurnal temperature amplitudes increase with increasing solar activity, but there is no analogous diurnal wind response. The thermospheric semidiurnal tide is much weaker than the diurnal tide.Semidiurnal temperature perturbations peak in the lower thermosphere where the semidiurnal forcing maximizes. The new in situ results must be combined with the GSWM upward propagating tide in the lower thermosphere, because the upward propagating components dominate the semidiurnal response throughout the region and the diurnal response below •0130 kin. In situ forcing accounts for most of the diurnal response aloft. Our preliminary evaluation of the GSWM thermospheric predictions is inconclusive. More extensive evaluations are necessary to make a firm assessment of whether the model captures the salient features of the seasonal and solar cycle variability of thermospheric tides.

Longitudinal, seasonal and solar cycle variation in lunar tide influence on the equatorial electrojet

“…It is clear that the change in solar activity may not have a direct significant effect on atmospheric tides in the ionospheric dynamo region (Bremer et al, 1997;Hagan et al, 2001), but the lunar tide amplitude intensification during solar maximum periods could be due to increased ionospheric conductivity. Ionospheric current intensity is dependent not only on the winds that drive the ionospheric dynamo but also on ionospheric conductivity, which depends on the intensity of the ionospheric electron density that is largely influenced by solar activity.…”

Intensive radiosonde observations of the diurnal tide and planetary waves in the lower atmosphere over Yichang (111°18' E, 30°42' N), China

“…6 and 7, respectively. For the purpose of comparison, the numerical model results from the Global Scale Wave Model 2000 (GSWM-00) (Hagan et al, 2001) and GSWM-02 (Hagan and Forbes, 2002) are also given in Figs. 6 and 7.…”

“…gravity waves (GWs), tidal waves and planetary waves (PWs), which are believed to impact significantly on local and global atmospheric climatology (Alexander and Pfister, 1995;Alexander, 1998;Batista et al, 2004;Kishore et al, 2004). It is extensively accepted that these atmospheric waves are mainly excited in the lower atmosphere (Forbes and Leveroni, 1992;Smith, 1997;Hagan et al, 2001;Hagan and Forbes, 2002;Fritts and Alexander, 2003;Batista et al, 2004).…”

WHU VHF radar observations of the diurnal tide and its variability in the lower atmosphere over Chongyang (114.14° E, 29.53° N), China

“…On the basis of observational and theoretical research in the recent decades, comprehensive understanding about the seasonal variability of tidal sources and background winds has been achieved (Hagan et al, 2001), and the primary seasonal variability of tides has been subsequently demonstrated. As the most widely accepted tidal models, the global-scale wave models (GSWMs) can provide the monthly averaged tides in the height range of 0-124 km and clearly display the latitude and season variability of tides.…”