Estimating Low-Level Tetroon Trajectories

Abstract

Return tag information from a number of low-level, constant volume balloons (tetroons), tracked by radar for some tens of miles in air diffusion studies, has extended the useful horizon of these atmospheric tracers to several hundred miles. Trajectories reconstructed at several levels have shown that the best approximation to the tetroon recovery point is an adjusted surface wind trajectory. The speed adjustment factor, derived from the “power-law” wind speed profile, varied from 1.6 to 1.8, individual values being dependent upon the tetroon float level. The direction adjustment amounted to 1 deg of veering per 100 ft. The approximation breaks down in frontal systems and over mountainous terrain. The “second standard level” and surface geostrophic wind trajectories are, on the average, less representative of the low-level flow as deduced from tetroon recovery points. These results have application in determining the transport of low-level air pollutants.