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Spectral characteristics of surface layer turbulence over the sea
Author(s) -
Nicholls S.,
Readings C. J.
Publication year - 1981
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.49710745309
Subject(s) - spectral line , turbulence , wind shear , wind speed , atmospheric sciences , convection , dissipation , convective boundary layer , humidity , boundary layer , planetary boundary layer , instrumentation (computer programming) , surface layer , environmental science , meteorology , geology , physics , mechanics , materials science , layer (electronics) , astronomy , computer science , composite material , thermodynamics , operating system
Airborne measurements of atmospheric turbulence spectra and cospectra made at low levels in convective boundary layers over the sea around the UK are presented. Both along‐wind and across‐wind sampled data are considered. In general, the former agree well with the results of other workers obtained over the sea using surface based instrumentation, though their temperature spectra differ significantly. the present along‐wind data are also compared with corresponding results obtained over land. Again the velocity spectra agree closely but the temperature spectra differ appreciably. the along‐wind humidity spectra obtained over the sea closely resemble the over land temperature spectra. No corresponding measurements are available to compare with the across‐wind sampled spectra. Both along‐ and across‐wind spectra vary with stability, increases in convective activity being associated with increased energy at low wave‐numbers. No corresponding change was observed in the cospectra. A comparison of along‐ and across‐wind sampled spectra and cospectra reveals considerable differences. These are consistent with a redistribution of energy from high to low wave‐numbers on changing from across‐ to along‐wind sampling. Thus the across‐wind spectra and cospectra appear more narrow (by about one decade). Spectral and cospectral peaks are also shifted. These observations are consistent with the stretching effects of the mean velocity shear acting on convective elements. The dissipation parameters derived from the high frequency parts of the spectra appear quite reasonable though there is a systematic difference between those derived from vertical and horizontal velocity spectra.