Deposition of aerially applied BT in an oak forest and its prediction with the FSCBG model

Journal of Applied Meteorology
By: , and 

This publication was funded by extramural grants, and has no U.S. Geological Survey (USGS) affiliated authors or editors. Hence, it was not required to conform to the USGS Fundamental Science Practices as described in the USGS Survey Manual .

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Abstract

Data are provided from 17 single-swath aerial spray trials that were conducted over a fully leafed, 16-m tall, mixed oak forest. The distribution of cross-swath spray deposits was sampled at the top of the canopy and below the canopy. Micrometeorological conditions were measured above and within the canopy during the spray trials. The USDA Forest Service FSCBG (Forest Service-Cramer-Barry-Grim) model was run to predict the target sampler catch for each trial using forest stand, airplane-application-equipment configuration, and micrometeorological conditions as inputs. Observations showed an average cross-swath deposition of 100 IU cm−2 with large run-to-run variability in deposition patterns, magnitudes, and drift. Eleven percent of the spray material that reached the top of the canopy penetrated through the tree canopy to the forest floor.

The FSCBG predictions of the ensemble-averaged deposition were within 17% of the measured deposition at the canopy top and within 8% on the ground beneath the canopy. Run-to-run deposit predictions by FSCBG were considerably less variable than the measured deposits. Individual run predictions were much less accurate than the ensemble-averaged predictions as demonstrated by an average root-mean-square-error (rmse) of 27.9 IU CM−2 at the top of the canopy. Comparisons of the differences between predicted and observed deposits indicated that the model accuracy was sensitive to atmospheric stability conditions. In neutral and stable conditions, a regular pattern of error was indicated by overprediction of the canopy-top deposit at distances from 0 to 20 m downwind from the flight line and underprediction of the deposit both farther downwind than 20 m and upwind of the flight line. In unstable conditions the model generally underpredicted the deposit downwind from the flight line, but showed no regular pattern of error.

Publication type Article
Publication Subtype Journal Article
Title Deposition of aerially applied BT in an oak forest and its prediction with the FSCBG model
Series title Journal of Applied Meteorology
DOI 10.1175/1520-0450(1992)031<1457:DOAABI>2.0.CO;2
Volume 31
Year Published 1992
Language English
Publisher American Meteorological Society
Contributing office(s) Toxic Substances Hydrology Program
Description 10 p.
First page 1457
Last page 1466
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