Numerical Simulation of a Breaking Gravity Wave Event Over Greenland Observed During Fastex

摘要

Measurements from the NOAA G4 research aircraft and high-resolution numerical simulations are used to study the evolution and dynamics of a large- amplitude gravity wave event over Greenland that took place on 29 January 1997 during the Fronts and Atlantic Storm-Track Experiment (FASTEX). Vertical cross section analyses of continuous flight-level and dropwindsonde data, with 50-km horizontal spacing, documented the presence of a large-amplitude breaking gravity wave extending from above the 180 hPa level to 500 hPa. The dropwindsonde data measured deep layers with isentropic overturning and an upshear tilt to the gravity wave. Flight-level data ((sup caret)180 hPa or 12 km) indicate a horizontal shear of over 0.001/s across the breaking wave with 25 K potential temperature perturbations. The wind speed downstream of the breaking wave decreased by 30 m/s resulting in the reduction of the cross mountain flow to near zero with localized regions of flow reversal.