The new Horizontal Wind Model (HWM07) provides a statistical representation of the horizontal wind fields of the Earth's atmosphere from the ground to the exosphere (0–500 km). It represents over 50 years of satellite, rocket, and ground‐based wind measurements via a compact Fortran 90 subroutine. The computer model is a function of geographic location, altitude, day of the year, solar local time, and geomagnetic activity. It includes representations of the zonal mean circulation, stationary planetary waves, migrating tides, and the seasonal modulation thereof. HWM07 is composed of two components, a quiet time component for the background state described in this paper and a geomagnetic storm time component (DWM07) described in a companion paper.

Recent theoretical studies have emphasized the probable importance of internal gravity waves in balancing the momentum budget of the mesosphere. In this paper, we propose a method by which the vertical flux of horizontal momentum can be measured by ground based radars. The method uses two or more radar beams each offset from the vertical to measure the atmospheric motions by the Doppler technique. Provided there is horizontal homogeneity, the momentum flux is proportional to the difference of the variances of the Doppler velocities measured in each beam. The flux convergence and, hence, the associated body force acting on the atmosphere can be inferred by measuring the flux as a function of height. It is shown that mean wind components can also be measured by this method and, under certain circumstances, so can the horizontal wavelengths and phase velocities of the internal waves. Observations of the vertical flux of zonal momentum made with this technique using an HF radar located near Adelaide,... Abstract Recent theoretical studies have emphasized the probable importance of internal gravity waves in balancing the momentum budget of the mesosphere. In this paper, we propose a method by which the vertical flux of horizontal momentum can be measured by ground based radars. The method uses two or more radar beams each offset from the vertical to measure the atmospheric motions by the Doppler technique. Provided there is horizontal homogeneity, the momentum flux is proportional to the difference of the variances of the Doppler velocities measured in each beam. The flux convergence and, hence, the associated body force acting on the atmosphere can be inferred by measuring the flux as a function of height. It is shown that mean wind components can also be measured by this method and, under certain circumstances, so can the horizontal wavelengths and phase velocities of the internal waves. Observations of the vertical flux of zonal momentum made with this technique using an HF radar located near Adelaide,...