Atmospheric stability determination at different time intervals for determination of aerial application timing

Authors: Huang, Yanbo; THOMSON, STEVEN - National Institute Of Food And Agriculture (NIFA)

Submitted to: Journal of Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 12/1/2016
Citation: Huang, Y., Thomson, S. 2016. Atmospheric stability determination at different time intervals for determination of aerial application timing. Journal of Biosystems Engineering. 41(4):337-341.

Interpretive Summary: Determination of atmospheric conditions for proper timing of spray application on crop field is important to prevent off-target movement of crop protection materials. Scientists in USDA-ARS Crop Production Systems Research Unit, Stoneville, Mississippi conducted a statistical analysis to determine the possibility of occurance of unfavorable atmospheric conditions to avoid off-target loss of aerial application. The statistical analysis was conducted with the weather data sampled in 5 min, 15 min and one hour for different purposes. The results illustrated that all the data measured in the Mississippi Delta consistently indicated that unfavorable conditions primarily happened between the hours of 6:00 PM and 6:00 AM during clear conditions in the summer days. The results further indicated that the atmospheric stability could be determined at different time intervals with consistent recommendations for when aerial application can be performed.

Technical Abstract: Determination of atmospheric conditions for proper timing of spray application is important to prevent off-target movement of crop protection materials. Susceptible crops can be injured downwind if proper application procedure is not followed. In our previous study, hourly data indicated unfavorable conditions primarily between the hours of 6:00 PM and 6:00 AM during clear conditions in the hot summer months in the Mississippi Delta. With the requirement of timely farm operations, sub-hourly data are needed to provide better guidelines for pilots since conditions of atmospheric stability can change rapidly. Although hourly data can be interpolated to some degree, finer resolution for data acquisition on the order of 15 minutes would provide pilots with more accurate recommendations to match up the data recording frequency of local weather stations. For the present study, temperature and wind speed data obtained at a meteorological tower were re-sampled for calculation of the atmospheric stability ratio for sub-hour and hourly recommendations. High-precision determination of temperature inversion periods influencing atmospheric stability was examined for strength, time of occurrence, and duration. The results indicated that the atmospheric stability could be determined at different time intervals with consistent recommendations for aerial applicators to avoid temperature inversion with minimal off-target drift of the sprayed liquid.