Dispersion of Fine Spray from Aerial Applications in Stable Atmospheric Conditions

A field study of aerial spray movement and dispersion was conducted at the New Mexico State University spray study site on the USDA Jornada Desert research ranch in April 2005. The purpose of the study was to measure the plume movement and in-plume spray concentrations of very fine droplets applied during calm, stable atmospheric conditions. Spray plume movement and dispersion were measured and recorded with a portable elastic-backscatter lidar. Supporting meteorology and air turbulence measurements were made simultaneously with 3-D sonic anemometers. A Cessna T188C equipped with Micronair AU5000 rotary atomizers produced small droplets (volume mean diameter of 37.3 m). The amount of spray material remaining in the air decreased rapidly for 1 to 2 min, and thereafter remained nearly constant and drifted as a definable plume with the slight air currents.