Descending Reflectivity Core (DRC) Research Page
What is the DRC?
Definition
As defined in Rasmussen et al. (2006), the DRC is a protuberence of reflectivity that descends from the echo overhang in the right-rear flank of a supercell (Fig. 1). To insure seperation from the main precipitation core, the DRC must have a reflectivity 4dB greater than the path of maximum reflectivity along the appendage to the core (Fig. 2). This 4dB requirement is an arbitrarily chosen value that appears to encapture most DRCs. Many DRCs, however, have reflectivity maximas greater than 8-10dB while some even reach values of 20+dB. The significance of this magnitude is still unknown, however. Typically orginating from 3-6km AGL, the DRC can take anywhere from 5-15 minutes to descend to the surface. Once this blob of reflectivity reaches the surface, it can either create an echo appendage or intensify reflectivity within a pre-existing one. In single-Doppler velocity data, the DRC is often associated with an enhanced region of rear-to-front, low-level flow. Because the rear-to-front flow is spatially isolated, this velocity signature can be straddled by a pair of counter-rotating vortices (Fig. 3). In some cases, the cyclonic vortex is associated with an incipient tornado. In one case (the Geary, OK supercell of 29 May 2004), the descent of the DRC was followed by anticyclonic tornadogenesis!
Importance of the DRC
With its spatial and temporal promiximity to tornadoes, the DRC is an intriguing feature. First and foremost, the possibility exists that the DRC is a precurser to tornadogenesis, and thus a warning-decision making tool. Second of all, the DRC might be the radar evidence of a dynamic process responsible for tornado formation. These two possibilities drive the need for ongoing and future research.
Section 1: Background - What is the DRC?(coming soon)