Abstract
<strong class="journal-contentHeaderColor">Abstract.</strong> The Global-Scale Wave Model (GSWM) is a steady-state two-dimensional linearized model capable of simulating the solar tides and planetary waves. In an effort to understand the capabilities and limitations of the GSWM throughout the upper mesosphere and thermosphere a comparative analysis with observational data is presented. A majority of the observational data used in this study was collected during the World Day campaign which ran from 20 January to 30 January 1993. During this campaign data from 18 ground-based observational sites across the globe and two instruments located on the UARS spacecraft were analyzed. Comparisons of these data with the simulations from the GSWM indicate that the GSWM results are in reasonable agreement with the observations. However, there are a number of cases where the agreement is not particularly good. One such instance is for the semidiurnal tide in the northern hemisphere, where the GSWM estimates may exceed observations by 50% . Through a number of numerical simulations, it appears that this discrepancy may be due to the eddy diffusivity profiles used by the GSWM. Other differences relating to the diurnal tide and the quasi-two-day wave are presented and discussed. Additionally, a discussion on the biases and aliasing difficulties which may arise in the observational data is also presented.
Highlights
During the 10 days from 20 January to 30 January, 1993, a coordinated ground- and spaced-based observational campaign of the mesosphere and lower thermosphere was conducted
Day (LTCS-9/MLTCS-5) campaign which lasted for 10 days
With data from 18 ground-based sites and two instruments located on the UARS satellite this data set provides the means to assess the ability of the GlobalScale Wave Model (GSWM) to simulate the solar tides and the quasi-two-day wave in the lower thermosphere
Summary
During the 10 days from 20 January to 30 January, 1993, a coordinated ground- and spaced-based observational campaign of the mesosphere and lower thermosphere was conducted. The focus of this paper is to assess how accurately the GSWM describes the salient features of the mesospheric and lower-thermospheric wind ®eld during January In this comparison it will be obvious that there are some signi®cant dierences between the ground-based and satellite-based estimates of mean, tidal, and planetary wave parameters. The campaign period during January 1993 was shortly following the December solstice and was characterized by low geomagnetic activity throughout the 10 understand the dynamical structure of the upper mesosphere and lower thermosphere This is the ®rst detailed comparison of the GSWM semidiurnal tidal predictions with observational data. Estimated power spectra for a subset of data from the ground-based radar stations are presented in Deng et al (1996) and indicate the presence of signi®cant wave activity at periods of 12 h (semidiurnal tide), 24 h (diurnal tide) and 48 h (quasi-two-day wave) during the campaign period. The relative strengths of these components change with both altitude and latitude
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