IHOP: do butterflies really trigger thunderstorms?

Bart Geerts

University of Wyoming

In IHOP (the International Water Vapor Project), the Wyoming Cloud Radar was used to study the convective boundary-layer, which was usually optically clear. The radar echoes are believed to be mostly insects. The first strong evidence for the life nature of these echoes comes from the observation that the echoes oppose the updrafts in which they find themselves caught, and more so when the updraft is stronger. This bio-response is key to the explanation of radar fine-lines, which forecasters over the years have come to monitor as the most likely loci of convective initiation. Several fine-lines were intercepted during IHOP, and the detailed echo and kinematic description of the vertical structure of such lines by the WCR is unprecedented. We examine one or two such cases, both leading up to the embryonic phase of severe thunderstorms.