A comparison of wind speed shears for frontal and undisturbed synoptic conditions

Wind speed shear parameters derived from data collected at a 481-m TV tower are computed for disturbed conditions (cold frontal passage), all undisturbed winds, undisturbed high winds, and undisturbed low winds. The exponential values of the wind speed power law for the case of disturbed conditions are found to be smaller than those for the case of all undisturbed winds, for practically all atmospheric stabilities; the largest exponential value (0.45) appears in the undisturbed low wind case at Richardson numbers near 0.25. The largest mean and standard deviations of the wind shear at the lowest layer (7–26 m) are 0.129 and 0.066 s ^-1, respectively, which occur for the high wind case at near-neutral stability. The most significant differences between the cases of disturbed and all undisturbed winds are that the former has much larger wind speeds and wind shear standard deviations in atmospherically-stable conditions.Work performed under the auspices of the U.S. Department of Energy.     

Some observations of eddy momentum fluxes within a maize canopy

Vertical momentum fiuxes measured by analog covariance equipment and hot-wire anemometers inside a dense canopy of mature maize vary exponentially with height above the ground. An attenuation coefficient of about 4 is indicated.This work was supported by the US Energy Research and Development Administration.Part of the Energy Research and Development Administration's Multistate Atmospheric Power Production Pollution Study (MAP³S).     

A method for measuring mean wind velocities in a canyon with tracer balloons

A method using balloons as tracers for measuring mean wind velocity in street canyons or mountain valleys has been developed. Tests of the method with numerical experiments showed that the method reproduced an assumed wind field quite well provided that the buoyancy component of the balloon velocity was larger than the downward velocity component of the wind. Tests of the method with measurements of wind velocity in a street canyon of downtown Chicago showed that the method yielded flow patterns quite similar to photographic results of flow visualization of phisical simulations by other investigators. However, no direct measurements of wind velocity were available for quantitative comparison.