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Horizontal and temporal variability of mountain waves over Mont Blanc
Author(s) -
Smith S. A.,
Broad A. S.
Publication year - 2003
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.02.148
Subject(s) - mesoscale meteorology , magnitude (astronomy) , flux (metallurgy) , geology , transect , spatial variability , momentum (technical analysis) , atmospheric sciences , meteorology , climatology , physics , oceanography , materials science , statistics , mathematics , finance , astronomy , economics , metallurgy
Aircraft observations of mountain waves over Mont Blanc during the 2 November 1999 Mesoscale Alpine Programme (MAP) case‐study are analysed. The present paper focuses on the horizontal and temporal variability of the wave field and its momentum fluxes. Results from the first Met Office Unified Model new‐dynamics simulation of a real mountain‐wave case are presented. The wave field and its fluxes are reproduced reasonably well considering the complexity of the problem. The wave momentum fluxes are observed to be extremely variable, which is surprising considering the stationarity of the wave field, although some variation is observed in the vertical‐velocity magnitude. The flux variability may result from the increasing midtropospheric wind shear with time. The simulated wind fields are used to investigate the horizontal variability in the wave field. The along‐track wave momentum flux is affected only slightly by a 2 km change in the position of the transect relative to Mont Blanc due to its displacement from the centre of the wave. More important in this particular case is the effect of the averaging length on the flux profile due to the limited downstream extent of the wave field, with large fluxes observed immediately over Mont Blanc. However, the position of the transect affects the apparent extent of the wave field and the magnitude of the variation in the cross‐wind component. © Crown copyright 2003.