Can VAD and DVAD Provide More Information?

The Velocity Azimuth Display (VAD, e.g., Browning and Wexler 1968) developed in 1960s has been used extensively in research and operations to deduce linear flow structures, such as mean wind, divergence and deformation surrounding a Doppler radar. Mathematically and physically, the VAD mean winds of a linear wind field at a given time/radar volume are the winds above the radar. The vertical profiles of horizontal winds, a standard WSR-88D product, have been interpreted as the “environmental wind” and assimilated into numerical models for weather prediction.

Recently, a reformulated VAD, Distance Velocity Azimuth Display (DVAD, Lee et al. 2014), demonstrated that the VAD mean winds will change for a moving weather system with linear winds (e.g., microburst) even when the system remains steady. For example, the increase of VAD winds with time can be a results of a steady linear wind system moving away from the radar rather than intensifying. Therefore, examining the VAD winds and other linear parameters together as a function of time should reveal additional information regarding the translation (motion) and evolution (intensifying or decaying) of a linear weather system.

We will use simple linear wind fields by varying intensity and translation speed to examine the trends and characteristics of the VAD/DVAD winds. These results can aid researchers and forecasters to better interpret weather systems’ characteristics for research and short-term weather forecasts using data from operational and research Doppler radars.