AN INTERCOMPARISON BETWEEN THE GSWM, UARS, AND GROUND-BASED RADAR OBSERVATIONS - A CASE-STUDY IN JANUARY 1993

The Global-Scale Wave Model (GSWM) is a steady-state two-dimensional l inearized model capable of simulating the solar tides and planetary wa ves. In an effort to understand the capabilities and limitations of th e GSWM throughout the upper mesosphere and thermosphere a comparative analysis with observational data is presented. A majority of the obser vational data used in this study was collected during the World Day ca mpaign which ran from 20 January to 30 January 1993. During this campa ign data from 18 ground-based observational sites across the globe and two instruments located on the UARS spacecraft were analyzed. Compari sons of these data with the simulations from the GSWM indicate that th e GSWM results are in reasonable agreement with the observations. Howe ver, there are a number of cases where the agreement is not particular ly 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 discre pancy may be due to the eddy diffusivity profiles used by the GSWM. Ot her differences relating to the diurnal tide and the quasi-two-day wav e are presented and discussed. Additionally, a discussion on the biase s and aliasing difficulties which may arise in the observational data is also presented.