MST Radar and Incoherent Scatter Radar Contributions to Studying the Middle Atmosphere

Abstract

We outline the development of Mesosphere-Stratosphere-Troposphere (MST) radar research of the middle atmosphere with special emphasis on coupling processes from above and below. The coupling from above is important in high-latitude auroral regions and we therefore include into our descriptions also the Incoherent Scatter (IS) radar observations used to study the lower thermosphere and ionosphere. The possibility of Joule heating of the mesosphere is discussed as well as transport processes and the influence of solar proton events on the mesosphere. A characterization of mesospheric VHF radar echoes is given and their relation to electron density changes discussed. Gravity wave velocity measurements with MST radars in the mesosphere and stratosphere are briefly presented, as well as profiles of the mean horizontal and vertical wind in the troposphere and stratosphere. It is discussed how ST radars could contribute to investigations of the polar stratosphere and the ozone variation. Also the fine structure of VHF ST radar echoes is considered in terms of a similar fine structure in temperature and ozone profiles. ST radars can also be used to study synoptic scale disturbances, troposphere-stratosphere transport by means of observations of tropopause foldings and mean vertical velocity. We finally point out how ST radars could be effectively implemented to study tropical waves and vertical transport between the troposphere and the stratosphere in the tropics during deep convection.