An Investigation of the Intermittent Turbulent Breakdown of the Nocturnal Planetary Boundary Layer
Abstract
A study of the statistic of the intermittent turbulent breakdown of the stable boundary layer over flat and complex terrain was made. The study is based on the temporal behavior of the covariance of wind speed and temperature, C sub ST. During a breakdown event, the overturning of the PBL results in high- speed warm air being transported downward toward the ground surface, and low- speed cool air being transported upward away from the ground surface. This results in a positive value of C Sub St and a consequent flux of heat toward the ground surface. The following general conclusions are reached: 1. Over uniform terrain, the characteristics of breakdown events differ between urban and rural environments. 2. Over complex terrain, the characteristics of breakdown events differ between high and low wind speed nights. 3. On average, the number of breakdowns per night is about 10 with an average duration of about 20 minutes. 4. In rural environments or for low wind speed nights in complex terrain, breakdown events make significant contributions to the nightly flux of heat to the ground surface.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 15, 1988
- Accession Number
- ADA204440
Entities
People
- Carment J. Nappo
Organizations
- Oak Ridge National Laboratory