The biometeorology of high-altitude insect layers: a case study

Many insect species are important pests, while others are significant natural enemies; hence monitoring their migration is important as it can tell us about their ecology and population dynamics. Meteorological conditions in the atmospheric boundary layer may have an important influence on the vertical distribution of migrating insects. The most notable pattern of vertical distribution of insects is layering, where the majority of insects fly at a specific height in the atmosphere. This work concentrates on nocturnal insect layering.

Most migrations occur at altitudes of several hundred metres, where they are difficult to observe, and therefore vertical-looking radar is well suited to probing vertical insect structure. The height the insects fly at is retrievable from the radar. Other important variables are insect speed and flight direction, mass, shape and wing-beat frequency. Profiles of meteorological variables have been retrieved from the UK Met Office’s Unified Model at the same location as the radar. Insect layers in vertical profiles were found to correspond with the existence of temperature inversions and nocturnal jets. Atmospheric humidity and turbulence were also explored. This work presents evidence that vertical insect distribution is strongly correlated with particular meteorological conditions.