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Abstract. Data taken by an imaging Doppler interferometer (IDI) 3.175-MHz radar during the

A set of tabulated functions called 'Hough Mode Extensions' (NM&), which represent numerical extensions of classical Hough modes into the viscous regime of the thermosphere, are used to leastsquares fit a climatological data base of tidal measurements. The data base consists of monthly average vertical profiles of semidiurnal amplitudes and phases at I7 radar sites accessing some part of the 80-I 50 km height region. The radars are distributed between 78 S and 70 N latrtude, and each one provides measurements of one or more of the following: eastward wind, southward wind, perturbation temperature. As a result of the fitting process. a single complex normalizing coefficient is derived for each month and for each of the four HMEs, designated (2,2), (?,3). (2.4) and (2.5) after their classical Hough function designatioI]s. Once the complex coefficients are derived, re~onstru~lion by weighted superposition of the HMEs results in globally continuous specifications of semidiurnal horizontal and vertical wind, temperature. pressure, and density throughout the X0-150 km height region. The tidal variations in density. in particular, provide greater accuracy for several aerospace applications. The methodology developed here can also be utilized to derive tidal lower boundary conditions for Thermospheric General Circulation Models (TGCMs), or as a basis for future empirical model development. Comparisons are also made with HME coefficients and global tidal field5 from the F~KHES and VIAL [(IY89) J. NII~MJS. /err. Ph~~s. St, 6491 numerical tidal model.

In 1961 at Adelaide the atmospheric turbulence near 90 km was measured month by month using a spaced‐station radio meteor technique. The characteristics of the large‐scale turbulent motions are found to be similar to those observed in the northern hemisphere. Characteristic velocities range from 23 to 40 m/sec and the large eddies are distinctly anisotropic; they have a horizontal scale of from 50 to 250 km and a vertical scale of 7 km, in keeping with a gravity wave source of turbulent energy. Shears measured over separations of 0.5 to 3.5 km are found to be characteristic of an apparently inertial spectrum, and the turbulent dissipation rate calculated from these shears shows a marked seasonal variation, with a maximum of 400 ergs/g sec in autumn and spring and a minimum of 160 ergs/g sec in summer and winter. There is a strong correlation between the seasonal variation of the turbulent dissipation rate and the energy of the 24‐hour component of the mean wind. The height shear is of particular interest, as, in keeping with rocket vapor trail wind analysis, it follows an approximate 1.4 power law.

The rate of diffusion of a trimethyl aluminum trail released by a Skylark rocket over Woomera, Australia (31°S, 137°E), in 1969 is interpreted in terms of molecular and turbulent diffusion, and is related to the scale of internal atmospheric gravity wave winds. Implications for disagreement between imaging Doppler interferometry and incoherent scatter radar winds are explored.