Real-time calculation of horizontal winds using multiple Doppler radars: A new WDSS-II module

As part of NSSL's new emphasis on multi-radar/multi-sensor analysis techniques for real-time applications, the authors set out to extend NSSL's Warning Decision Support System - Integrated Information (WDSS-II) to include a multi-Doppler capability for the calculation of the 3D wind field in regions of observed radial velocity data. To allow for maximum flexibility, in terms of the number of radars used as input sources, the “overdetermined dual-Doppler” analysis method is used. The multi-Doppler analysis method has been implemented as a new module to the multi-radar portion of WDSS-II. For a user-specified analysis domain, the multi-Doppler module calculates the three wind components (u, v and w) in regions where 2 or more Doppler radars are providing valid radial velocity measurements. The program generates output files of each wind component, along with a horizontal vector field (u and v combined), which are displayable via WDSS-II.

Unfortunately, initial test results of the new multi-Doppler module using data from various operational radars (both WSR-88D and TDWR) showed that the vertical velocity field quickly developed large errors, which also caused errors in the horizontal wind field. Since the main operational use of the multi-Doppler output is expected to involve the horizontal wind field versus the vertical velocity, a second version of the module was created that just calculates the u and v components (by assuming w = 0). Test results for this 2D horizontal-wind module on two severe weather events showed very good agreement between the u and v fields and corresponding radial velocity data.