Observations of the two-dimensional wind field in severe convective storms using a mobile, X-band, Doppler radar with a spaced antenna

Studies of severe convective storms require the characterization of the three-dimensional wind field as a function of time. During the spring of 2004, a mobile, X-band, Doppler radar from the University of Massachusetts, was outfitted with a 1-m spaced antenna. The spaced antenna permits the estimation of the cross-beam component of the wind in addition to the conventional along-the-beam component. The vertical component of the wind may be estimated from the continuity equation. The use of a spaced antenna in a Doppler radar is an alternative to a conventional dual-Doppler network. Although the beamwidth of the antenna is 2 degrees, which is twice the width of a typical mobile, X-band radar, when data from two radars are combined, the spatial resolution is degraded anyway, owing to the non-overlapping nature of data volumes. The scanning rate must be relatively slow, because it is necessary to record a sufficient number of samples to be able to estimate the cross-beam component. In a convective storm, however, there is need to probe volumes relatively quickly, owing to the rapid evolution of the wind field in it. Results from our first-time use of the spaced antenna will be given, along with an assessment of whether or not it is a viable technique.