Abstract
With certain limitations, atmospheric radars generally called MST (mesosphere, stratosphere, and troposphere) radars or ST (stratosphere and troposphere) radars are capable of continuously monitoring three-dimensional winds, waves, turbulence, and atmospheric stability over the wide altitude range 1-100 km in the Earth's atmosphere. In particular, direct measurement of venical wind velocity over such a wide attitude range is possible only with MST radars. Their time resolution of about 1 min and attitude resolution of 75-150 m are unequalled by conventional instruments (e.g., rawinsondes and rocketsondes), making it possible for MST radars to quantitatively investigate the small-scale atmospheric gravity waves that are considered to play important roles in the dynamics of the Earth's atmosphere. It is also noted that the vertical flux of horizontal momentum can be measured with high accuracy by MST radars. MST radars in the VHF band have the capability to discriminate echoes from clear air and precipitation particles, while microwave meteorological radars generally detect only precipitation echoes. In the last three decades, this excellent capability has been used extensively to study various dynamical disturbances in the Earth's atmosphere, developing new frontiers of atmospheric research on, primarily, mesoscale and micro-scale phenomena. In the present paper, these advances are reviewed briefly.
