Fine-scale layering on the edge of a stratospheric intrusion

Observations of vertical profiles of ozone, humidity, static stability and VHF radar vertical power at Aberystwyth (52°N, 4°W) on 21 June 1996 revealed a pronounced layered structure at the western edge of a stratospheric intrusion, in a location where one would expect to see a tropopause fold. Despite the 3 km depth of the observed ozone anomaly, it was not represented as a fold in the ECMWF potential vorticity analyses; nor was it evident as a layer of enhanced wind shear. Ozone lidar measurements suggest that the fine-scale layering gave way to a single layer as the day progressed. Weak sporadic turbulence observed by the radar at the edge of the fold showed some mixing between stratospheric and tropospheric air.