Casebook 15 July 2005
CSU-CHILL Casebook: 15 July, 2005
On 15 July 2005 a thunderstorm RHI scan was conducted through a storm located a short distance northeast of the CSU-CHILL radar at 2335 UTC. (See VCHILL example below.) The height of the 0 dB level varies with range through the echo. This level is associated with quasi-spherical and or tumbling ice particles. (The horizontally and vertically polarized return signal levels from such particles are essentially equal.) When these ice particles melt into raindrops, aerodynamic forces quickly deform the resultant drops into oblate shapes that produce positive values. In the VCHILL example image, melting is fairly complete in the lower portions of the reflectivity core located at a range of 36 km where the 0 dB level does not reach the surface. In contrast, the presence of frozen (non-aligned) hydrometeors (hailstones) is indicated at a range of 43 km. Also, the radial velocity patterns associated with a gust front are present at a range of 16 km.
