Accession Number : AD0635588

Title :   INVESTIGATION OF ENERGY, MOMENTUM AND MASS TRANSFERS NEAR THE GROUND.

Descriptive Note : Final rept. for 1965.

Corporate Author : CALIFORNIA UNIV DAVIS

Personal Author(s) : Brooks, F. A. ; Pruitt,W. O.

Report Date : JUN 1966

Pagination or Media Count : 248

Abstract : Half-hourly averages of field measurements of flux rates of heat and evaporation are reported in 1963, 1964, 1965. Selected examples of momentum flux and the three corresponding profiles of airspeed, temperature, and moisture are included. Crop plantings around the flat, 5-hectare site are described in detail, and the meteorological conditions are thoroughly documented. The observations reveal a wide range in the ratios of eddy diffusivities and rather high magnitudes for the Karman constant (about 0.45 - 0.55). Various aerodynamic, energy balance and other evaporation equations were checked against evapotranspiration data from the 6.1 meter weighing lysimeter. Results show the need for very significant diabatic correction of the aerodynamic expressions at low wind speeds. Statistical treatment removing the cyclic variation from the record of the shear-stress meter show that this 50-ton float follows the varying drag of wind gusts well within one minute. The revised profile formula (log law and power law) has been found to fit observations of airspeed and temperature about 30 per cent better than the conventional Monin-Obukhov formula. The illogical averaging of friction-eddy forced convection with buoyant-parcel natural convection is discussed and a tentative lower airspeed limit of 2 m/sec at a 2-meter height is proposed for application of edd-transfer formulas. Several concepts are discussed of flow regimes near the ground and detailed descriptions of instrumentation and calibration are included. (Author)

Descriptors :   (*MICROMETEOROLOGY, *EVAPOTRANSPIRATION), FLUID MECHANICS, METEOROLOGICAL PHENOMENA, THERMODYNAMICS, AGRICULTURE

Subject Categories : Agronomy, Horticulture and Aquiculture
      Meteorology

Distribution Statement : APPROVED FOR PUBLIC RELEASE