The potential effects of vertical wind direction shear on pollutant transport at a complicated, semiarid site are examined using tower measurements. This high-elevation site is situated on a sloping plateau between mountains to the west and a river valley to the east. The local climate, which favors clear skies, low humidity, and light winds, permits terrain-generated winds to develop frequently. During the night, winds that are oriented along the valley frequently overlie shallow (<50-m deep) drainage winds. Results indicate the nighttime direction shear between the levels at 92 and 12m above ground exceeds 60° 20% of the time and exceeds 20° 50% of the time. Daytime shear is more modest: it is less than 20° 90% of the time. The effects of vertical wind direction shear on plume transport are studied by performing two model simulations of release at 50 m above ground level during a period when strong directional shear persisted for several hours. In the simulation using the full wind profile, southwest winds above a shallow drainage layer initially transport material to a community located 2 km to the northeast of the release. However, when only the 12-m wind is used, the model predicts that the material impacts a different community located 10 km to the southeast. This simulation demonstrates that ignoring the vertical shear effects can result in serious mistakes in responding to an emergency.
CITATION STYLE
Bowen, B. M., Baars, J. A., & Stone, G. L. (2000). Nocturnal wind direction shear and its potential impact on pollutant transport. Journal of Applied Meteorology, 39(3), 437–445. https://doi.org/10.1175/1520-0450(2000)039<0437:NWDSAI>2.0.CO;2
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