Observations and numerical model simulation of a partially trapped lee wave over the Welsh mountains

Abstract

A large-amplitude lee-wave event detected in radiosonde ascents during a field experiment in the Welsh mountains is described and wave characteristics are deduced. The synoptic-flow pattern accompanying this wave field is used to initialize the UK Meteorological Office's nonhydrostatic mesoscale model (with a 3-km horizontal grid length) in an attempt to simulate the gravity-wave response over the Welsh mountains. After 4 h of integration time the resulting flow field is quasi-steady and exhibits a fairly regular wave field with a dominant wavelength at about 22 km and nearly vertical phase lines. Verification is achieved by comparing rate-of-ascent variations with model vertical velocity variations along the trajectory of a radiosonde: the agreement is very good. -from Author