Effect of Atmospheric Conditions on Coverage of Fogger Applications in a Desert Surface Boundary Layer

Abstract

Near-ground aerosol fogs were applied in the Chihuahua Desert of New Mexico, which has widely spaced, low shrub vegetation. Near-ground fog dispersion was measured remotely with a light detection and ranging (lidar) system. Local atmospheric turbulence and stability were continuously measured with 3-axis sonic anemometers during aerosol treatments. Lidar-measured plume area coverage and spread were related to the simultaneous local-scale weather, including both convective boundary layers (CBL) and stable boundary layers (SBL). A modified bulk stability ratio (SRm) was used to characterize the stability conditions near the ground. Time averages appropriate to the SBL were determined using the multidimensional decomposition technique and matched to the short spray time periods in the CBL. The widest, most effective, near-ground coverage was obtained from insect fogger applications conducted during relatively high wind speeds: U > 1 m s-1 in stable conditions, and U > 3 m s-1 in unstable conditions. In general, spraying during SBLs was more efficient than during CBLs, with less material wasted and better consistency of coverage in the target zone nearest the ground. There was no significant difference in spray coverage or plume dispersion between the handheld thermal fogger and the ultra-low volume (cold fogger) applicator used.