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Diurnal Variations In Flow Over A Succession of Ridges and Valleys
Author(s) -
Mason P. J.
Publication year - 1987
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 - 10.1002/qj.49711347804
Subject(s) - froude number , turbulence , flow (mathematics) , geology , mechanics , mean flow , meteorology , turbulence kinetic energy , geomorphology , physics
Observations of flow in a nearly two‐dimensional valley located within a succession of similar ridges and valleys are presented. Measurements of the mean flow have been made at all times of the day and are found to be well characterized by a suitably defined Froude number. the unstable and neutral daytime flow shows a flow separation whilst when the Froude number has a value of about two (usually around evening and dawn transitions) the flow is attached and the valley well ventilated. For smaller values of Froude number the flow speed in the valley reduces and a characteristic ‘drainage’ flow occurs. In addition to mean flow measurements and soundings of temperature structure, measurements were also made of turbulence energy and stress. This allows an estimate of the effective value of the surface roughness, z o , and an indication of the stability dependence of the momentum transfer to be made.