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An objective exposure correction method for average wind speeds measured at a sheltered location
Author(s) -
Wieringa J.
Publication year - 1976
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.49710243119
Subject(s) - anemometer , environmental science , wind speed , mesoscale meteorology , meteorology , wind direction , instrumentation (computer programming) , azimuth , roughness length , wind shear , remote sensing , wind profile power law , geology , physics , computer science , optics , operating system
The representativity of station wind measurements can be increased by elimination of sheltering effects caused by small‐scale obstacles. It is shown how correction factors for this purpose can be obtained for each wind azimuth sector from analog wind records of the station itself, by extracting maximum gust speeds during periods with strong wind. The transformation is achieved using a gust factor model (Wieringa 1973) which relates the ratio of maximum and average wind speed to measuring height, surrounding roughness and gust wavelength. The concept of ‘effective height’ is criticized. It is indicated how the actual duration of the recorded maximum gusts can be obtained from station instrumentation response specifications, and it is shown that this duration exceeds 10 seconds for the usual combination of cup anemometer and galvanometric recorder. A trial climatological application shows how omission of exposure correction may lead to exaggeration of mesoscale horizontal wind gradients.