Observations on the Growth of an Internal Boundary Layer with a Lidar Techniqueby Chia R. Chu, Natl Central Univ, Chungli, Taiwan,
Marc Parlange, Natl Central Univ, Chungli, Taiwan,
William Eichinger, Natl Central Univ, Chungli, Taiwan,
Gabriel Katul, Natl Central Univ, Chungli, Taiwan,
Abstract: The distribution of atmospheric water vapor across a step change in surface humidity (dry-wet) was observed by a Lidar measurement technique under neutral atmospheric stability condition. The technique uses multiple elevation scans from a scanning water Raman-Lidar to construct a time-averaged image of the variation in water vapor concentration with height and distance. The measurements were obtained from a bare soil field in California's central valley. The growth of the vapor blanket over the wet surface was identified by the spatial distribution of the specific humidity over the field. The height of the local humidity boundary layer under neutral atmospheric stability condition was observed to increase as δv ∝ X0.87, where x is the downstream distance from surface humidity discontinuity line. Evaporation rates calculated from the humidity profiles agreed satisfactorily with the fluxes independently measured using a lysimeter.
Subject Headings: Boundary layers | Imaging techniques | Humidity | Gases | Distance measurement | Evaporation | Measuring instruments | Spatial distribution | North America | California | United States
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