Characteristics of descending reflectivity cores observed by Ku-band radar

After tragic heavy rains and flash floods in metropolitan areas in 2008, we installed a Ku-band radar in Musashino-shi, Tokyo in 2011, in order to investigate such disasters. This radar was designed to get a 3D volume scan per minute, and therefore is expected to contribute to clarification of mechanisms of severe phenomena such as heavy rains, tornadoes and downbursts.

On September 1, 2012, a localized heavy rain occurred in Tokyo due to an upper cold low (UCL). In this case, some cells looked like westplains storm (Foote and Frank, 1983) or multi-core cell (Kim et al., 2012). We investigated characteristics of descending reflectivity cores (DRCs) observed by the Ku-band radar. As a result, it was revealed that DRCs had been generated at a height of about 4km and fell at about 7-8 m/s. In addition, as they fell successively in a short time, the area covered by echo > 25dBZ became wider near the ground.