Common orientation and layering of migrating insects in southeastern Australia observed with a Doppler weather radar

Abstract

Australia's migratory insects, including the Australian Plague Locust (Chortoicetes terminifera Walker), were observed with Doppler weather radar during the austral spring and summer of 2010-2011. On occasion, the presence of a dumbbell pattern in the reflectivity indicated insects taking a common orientation. Using the radial velocity, the average orientation and direction of travel of the insects were determined. Common orientation was most clearly observed shortly before or after dawn, and occasionally in the evening. However, signs of orientation were observed in different migrant populations throughout the day. The cases selected for this study described a daily cycle of migration phases and associated atmospheric conditions. The weather was characterized using surface observations, analysis charts and numerical weather prediction model fields. Migrating insects were profuse during convective weather. Insects often aggregated into layers, particularly in the vicinity of the nocturnal inversion. © 2013 Royal Meteorological Society.