Direct Measurement of Large‐Scale Vertical Velocities Using Clear‐Air Doppler Radars

Abstract

Radars that can make wind measurements in the clear air are expected to play an increasing role in meteorological observing systems in the future, especially for horizontal wind measurements. This paper considers the prospects for using these radars, which are sometimes called wind profilers, to also measure the large?scale vertical velocity. Unfortunately, all radars for which vertical velocity data are available at this time are located in or near mountains, where standing lee?wave effects often make the data representative of only small?scale features. Confining attention to those times when lee wave effects are not expected, case?study comparisons of the existing radar data with indirectly computed synoptic?scale motions suggest that time averaged radar data are representative of large?scale features smaller than the synoptic scale, perhaps more aptly termed subsynoptic?scale features. Results from a three?station radar network in France show that the time?averaged vertical velocities are usually nearly the same at all stations, although there are some differences, and suggest that the spatial scale of the flow features they represent is greater than 50 km. Over a long-term average, the net influence of lee wave effects at mountain sites is small, and radar measurements appear to be useful for climatological studies of vertical velocity in large?scale circulation systems.