Linking Dynamics of the Near-surface Flow to Deeper Boundary Layer Forcing in the Nocturnal Boundary Layer
Abstract
Weak-wind flow in the nocturnal boundary is one of the most poorly understood problems in the field of meteorology. The understanding of weak-wind flows is essential for the improvement of regulatory dispersion models which are currently rendered invalid under weak-wind conditions and stable stratification. Recently there have been increased efforts directed towards improving the understanding nocturnal boundary layer dynamics. The results of these studies have shown that nocturnal boundary layer flows are often dominated by intermittent turbulence and motions occurring on horizontal scales ranging from hundreds of meters to several kilometers and on time scales of 1 minute to 1 hour. We refer to these scales as sub-meso. This connection has led to the hypothesis that intermittent turbulence generation may be the result of sub-meso motions that are subject to external forcing originating in the deeper boundary layer. However, these processes have proven difficult to measure as traditional sensor networks have failed to provide the vertical and horizontal coverage necessary to observe the driving forces on these scales. This study sought to close this knowledge gap using SOund Detection And Ranging (SODAR). SODAR is a ground based acoustic remote sensing technology that is capable of measuring wind and turbulence at multiple heights in the boundary layer. Data were collected with a pair of SODAR systems with sequentially increasing separation distance at the Oregon State University Botany and Plant Pathology lab during the summer of 2010. The data have indicated that motion occurring on time scales of 2 minutes to 32 minutes are isolated to the lowest 50 meters of the nocturnal boundary layer. Surface-layer measurements were collected using a pair of sonic anemometers placed at heights of 1.5 and 7 meters above ground level.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2012
- Accession Number
- ADA563740
Entities
People
- Alexander R. Smoot
Organizations
- Oregon State University