Wednesday, 16 January 2002: 2:00 PM
Wind Shear and Turbulence Profiling with Meteorological Radar
When the environmental wind field is horizontally homogeneous over a sufficiently large area, accurate wind profiles can in principle be obtained by Doppler radars using some form of the VAD technique. The existence of a large network of NEXRAD radars operating continuously across the United States makes this a potentially highly valuable source of information. However, a couple sources of systematic error make the deduction of accurate wind profiles problematic. These are contamination by migratory birds and ground clutter contamination. Both of these problems can lead to highly inaccurate wind profiles. Both are difficult to detect. Furthermore, it is not always possible to filter out their effects. This paper will document the extent of these problems and suggest methods to minimize their impact.
We have also attempted to derive turbulence profiles by using methods based on VAD techniques. Turbulence at scales larger than the radar probe volume is deduced by the variance in the VAD. To deduce small-scale turbulence, we make use of the spectral width information. This information combines measures of turbulence and vertical wind shear. A technique to separate these two effects is described. This technique is also sensitive to the effects of birds and ground clutter; however, potentially less so than the mean velocity estimates. Consequently, the wind shear deduced from spectral width information is potentially more accurate than the wind shear deduced by differentiating the vertical wind profile obtained by VAD.