Layers of nocturnal insect migrants at high-altitude: the influence of atmospheric conditions on their formation
Abstract:• Radar studies of nocturnal insect migration have often found that the migrants tend to form well-defined horizontal layers at a particular altitude.
• In previous short-term studies, nocturnal layers were usually observed to occur at the same altitude as certain meteorological features, most notably at the altitudes of temperature inversion tops or nocturnal wind jets.
• Statistical analyses are presented of 4 years of data that compared the presence, sharpness and duration of nocturnal layer profiles, observed using continuously-operating entomological radar, with meteorological variables at typical layer altitudes over the U.K.
• Analysis of these large datasets demonstrated that temperature was the foremost meteorological factor that was persistently associated with the presence and formation of longer-lasting and sharper layers of migrating insects over southern U.K.