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The temperature fluctuations in stable stratification
Author(s) -
Okamoto M.,
Webb E. K.
Publication year - 1970
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.49709641003
Subject(s) - quiet , turbulence , physics , intensity (physics) , spectral density , atmospheric sciences , mathematics , mechanics , optics , statistics , quantum mechanics
The intensity and spectrum of temperature fluctuations recorded at a height of 2 m over flat grassland in stable conditions are examined. Thr results show a demarcation between two distinct régimes, ‘ turbulent ’ for Ri less than a critical value of about 0.2 and ‘ quiet ’ for larger Ri. The magnitude of the temperature fluctuations, scaled relative to z δ z , is comparatively large in the turbulent régime, decreases as Ri increases towards the critical value, and remains small in the quiet régime. The temperature, while always of a typically turbulent character in the turbulent régime, is of variable behaviour in the quiet régime ‐ intermittently quiescent with occasional isolated smooth pulses (usually negative), or wave‐like with assorted frequencies, or turbulent. In the turbulent régime, the spectrum approximates to the − 5/3 power form for normalized frequencies nz/U greater than 0.6. In the quiet régime, the form of the spectrum varies unpredictably from one occasion to another.