Formation of the Enhanced-V Infrared Cloud-Top Feature from High-Resolution Three-Dimensional Radar Observations

Abstract

he responsible mechanism for the formation of the enhanced-V infrared cloud-top feature observed above tropopause-penetrating thunderstorms is not well understood. A new method for the combination of volumetric radar reflectivity from individual radars into three-dimensional composites with high vertical resolution (1 km) is introduced and used to test various formation mechanisms proposed in the literature. For analysis, a set of 89 enhanced-V storms over the eastern continental United States are identified in the 10-yr period from 2001 to 2010 using geostationary satellite data. The background atmospheric state from each storm is determined using the Interim ECMWF Re-Analysis (ERA-Interim) and radiosonde observations. In conjunction with the infrared temperature fields, analysis of the radar data in a coordinate relative to the location of the overshooting convective top and in altitudes relative to the tropopause suggests that above-anvil (stratospheric) cirrus clouds are the most likely mechanism for the formation of the enhanced V.