The Use of Insects as Tracers for “Clear-Air” Boundary-Layer Studies by Doppler Radar

Abstract

Abstract Single- and multiple-Doppler radar systems are increasingly being used to monitor circulations within the clear-air boundary layer where the scatterers may be gradients of the refractive index or biota or a combination of both. When insects are the primary source of returned radar power, it must be assumed that the insects are either small and are being carried passively in the air, or are flying randomly so that the bulk velocity of all the insects contained within a pulse volume is zero relative to the air. This study presents dual-polarization radar observations of the interaction between a gust flow and a deep cloud of insects within a relatively unstable air mass over North Dakota on 4 July 1987. These data are unique in that they reveal several meteorological conditions for which the preceding assumption is not valid. The boundary layer was not capped, and circulations rose above an apparent threshold altitude above which these insects were not flying. Temperatures near the threshold altitu...