Urban Effects on the Properties of Radar First Echoes

Abstract

The properties of 3 cm radar first echoes were used to study the effects of the St. Louis, Missouri metropolitan area on precipitation initiation during the summer months of Project METROMEX. Good statistical support was found for a ?150 m lowering of urban first echo tops and a ?250 m lowering of urban first echo bases when compared to rural echoes observed on the same day. Urban echoes were found to be thicker than their rural counterparts; however, there is no statistical support for this difference. This result is most easily interpreted as suggesting a slight weakening of the updraft in urban clouds.