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- Author or Editor: James K. Angell x
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Abstract
Discussed is the use of tetroons to obtain estimates of the Reynolds stresses, the rate of production of eddy kinetic energy through these stresses, the coefficient of eddy viscosity, and the viscous dissipation within the planetary boundary layer. At an average height of about 3000 ft. (admittedly in the upper portion of the boundary layer) the tetroons yield a mean value for the zonal Reynolds stress of 1.5 dynes/cm2. This value increases by a factor of three as the lapse rate increases by a factor of one-half. The tetroons yield an average value for the rate of production of eddy kinetic energy through Reynolds stresses of 5.4 cm.2/sec.2, but this value is probably an underestimate inasmuch as the tetroons appear systematically to underestimate the wind shear in the vertical. The rate of production of eddy kinetic energy through Reynolds stresses decreases radically with increase in lapse rate. On the average, both of the above parameters increase with increase in the 3000-ft wind speed.
The mean tetroon-derived value for the coefficient of eddy (dynamic) viscosity is 0.57×103 gm. cm.−1 sec.−1 This mean value appears somewhat large (in accord with the above-mentioned underestimate of the vertical shear) and the scatter of inividual flight values suggests that this may be too sensitive a parameter to estimate from the tetroon data.
Equating the rate of production of eddy kinetic energy through Reynolds stresses to the dissipation appears to yield too large a value for the dissipation. Consequently, buoyancy and flux divergence terms probably can not be neglected and it may be necessary to place temperature instruments on the tetroons before acceptable dissipation estimates can be obtained.
Abstract
Discussed is the use of tetroons to obtain estimates of the Reynolds stresses, the rate of production of eddy kinetic energy through these stresses, the coefficient of eddy viscosity, and the viscous dissipation within the planetary boundary layer. At an average height of about 3000 ft. (admittedly in the upper portion of the boundary layer) the tetroons yield a mean value for the zonal Reynolds stress of 1.5 dynes/cm2. This value increases by a factor of three as the lapse rate increases by a factor of one-half. The tetroons yield an average value for the rate of production of eddy kinetic energy through Reynolds stresses of 5.4 cm.2/sec.2, but this value is probably an underestimate inasmuch as the tetroons appear systematically to underestimate the wind shear in the vertical. The rate of production of eddy kinetic energy through Reynolds stresses decreases radically with increase in lapse rate. On the average, both of the above parameters increase with increase in the 3000-ft wind speed.
The mean tetroon-derived value for the coefficient of eddy (dynamic) viscosity is 0.57×103 gm. cm.−1 sec.−1 This mean value appears somewhat large (in accord with the above-mentioned underestimate of the vertical shear) and the scatter of inividual flight values suggests that this may be too sensitive a parameter to estimate from the tetroon data.
Equating the rate of production of eddy kinetic energy through Reynolds stresses to the dissipation appears to yield too large a value for the dissipation. Consequently, buoyancy and flux divergence terms probably can not be neglected and it may be necessary to place temperature instruments on the tetroons before acceptable dissipation estimates can be obtained.
