“…Since that time monthly climatologies of zonal mean winds and temperatures based on empirical or semiempirical models (Batten, 1961;Kantor and Cole, 1964;Murgatroyd, 1965;Murphy, 1969;CIRA (1972); U.S. Standard Atmosphere (1976)) have been routinely employed in linear tidal models (Walterscheid et al, 1980;Aso et al, 1981;Forbes, 1982;Vial, 1986;Forbes and Hagan, 1988;Forbes and Vial, 1989) to account for these effects. used a series of background wind models (Groves, 1985(Groves, , 1987Portnyagin and Solov'eva, 1992a,b) and the socalled MSISE-90 temperature model (Hedin, 1991) in the initial formulation of the linear tidal and planetary wave model known as GSWM. Recently, Hagan et al (1999) updated the GSWM background wind field between ∼10 and 120 km with multi-year monthly averaged HRDI zonal mean zonal wind data.…”