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United States Department of Agriculture

Agricultural Research Service

Title: Measurement and Analysis of Atmospheric Stability in Two Texas Regions

Author
item Fritz, Bradley

Submitted to: American Society Agricultural Engineers/National Aerial Applicators Assoc
Publication Type: Proceedings
Publication Acceptance Date: December 8, 2003
Publication Date: December 8, 2003
Citation: Fritz, B.K. 2003. Measurement and analysis of atmospheric stability in two Texas regions. In: Proceedings of the American Society of Agricultural Engineers/National Agricultural Aviation Association Technical Session, December 6-10, 2003, Reno, Nevada. Paper No. AA03-005.

Interpretive Summary: Drift from aerial application of crop protection and production materials is influenced by both controllable factors such as nozzle type spray measure and uncontrollable conditions such as wind speed and atmospheric stability. Applicators are responsible for considering atmospheric conditions and adjusting operational factors to reduce the potential for drift. Generally, greater atmospheric stability is associated with greater drift potential. Meteorological variables were monitored at two Texas locations and probability assessment of daily atmospheric stability variation was developed. Generally, the greatest potential for drift due to stable atmospheric conditions occurs during the late afternoon. These results provide guidance to applicators on the daily cycle of atmospheric stability and the most appropriate application times to avoid potential drift. In addition, these results are being used to plan field studies to document drift associated with the various classes of atmospheric stability.

Technical Abstract: Drift from aerial application of crop protection and production materials is influenced by many factors for which the applicator is responsible for considering and adjusting, where applicable, to reduce as much as possible, the potential drift. In an effort to study the uncontrollable factors, this study monitored and documented atmospheric conditions over the course of several months at two locations in Texas. The measured meteorological data was used to assess how atmospheric stability varied as a function of time of date, location, and other meteorological conditions. Additionally, inversion periods were examined for strength, time of occurrence, and duration. Stable and very stable atmospheric conditions, which would tend to produce the most drift, primarily occurred between the hours of 6 p.m. and 6 a.m., with a few occurrences between 6 a.m. and 6 p.m. Between the hours of 6 a.m. and 6 p.m. unstable atmospheric conditions tended to be dominate. Of the days monitored, almost half experienced inversion periods between the hours of 6 a.m. and 6:30 p.m., with more than half of these inversion periods being after 4 p.m. and having durations an order of magnitude greater than periods of inversions seen between 6 a.m. and 4 p.m. Generally, these late afternoon periods are of most concern as the probability of experiencing increasingly stable conditions or long inversion period increases.

Last Modified: 10/20/2014
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