Comparison of lateral and vertical diffusion in several valleys

Conference · Sat Jan 01 04:00:00 EST 1983

OSTI ID:6624207

Barr, S

The turbulent dispersion of tracers nocturnal in four valleys was examined. Two are reasonably large with greater than 600-m terrain relief and two are well-formed but are shallow and narrow. Both Anderson Creek, California and Parachute Creek, Colorado are large and deep enough to produce a systematic cool air drainage wind regime although the difference in valley shapes makes the structure of that wind field quite different. Parachute Creek is a deep linear valley in which a vigorous down-valley flow develops and exits at the mouth without significant obstruction. Anderson Creek is a three-dimensional bowl with a very flat outflow region from which the cool air backs up to form a quasi-stagnant pool 200 to 300 m deep. Inhomogeneous turbulence is a major factor in the transport history of tracers in Anderson Creek. In the slope-wind potion of the basin the plume growth is systematic and about 1.5 to 2 Pasquill-Gifford categories more vigorous than estimated by radiation and windspeed. The slower mean wind and greater meandering that the plume encounters in the cool air pool makes a distinct change in the tracer cloud behavior. Residence times are long and the apparent width of a time integrated plume is much greater than predicted by plume model considerations. The two small-scale terrain features, Corral Gulch and Los Alamos Canyon, tend to channel the wind generated locally on the next larger scale but produce only weak, shallow slope-wind characteristics themselves. The gross diffusion is more vigorous by about one Pasquill-Gifford category than indicated by the radiation- windspeed system and is consistent with measured sigma/sub A/ values. Both valleys tend to constrain the lateral spread of tracer. Vertical growth estimates suggest that plumes can grow above the height of the valley walls. It is reasonable to expect that material thus exhaled by a valley is distributed in the surrounding area including adjacent valleys.

• Research Organization: Los Alamos National Lab., NM (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6624207
• Report Number(s): LA-UR-82-3297; CONF-830307-3; ON: DE83003570
• Country of Publication: United States
• Language: English

Related Subjects

500100 -- Environment
Atmospheric-- Basic Studies-- (-1989)
500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION
CALIFORNIA
COLORADO
COMPARATIVE EVALUATIONS
DIFFUSION
DILUTION
ENVIRONMENTAL TRANSPORT
FEDERAL REGION IX
FEDERAL REGION VI
FEDERAL REGION VIII
ISOTOPE APPLICATIONS
MASS TRANSFER
MATHEMATICAL MODELS
METEOROLOGY
NEW MEXICO
NOCTURNAL VARIATIONS
NORTH AMERICA
PLUMES
POLLUTION
TRACER TECHNIQUES
TURBULENCE
USA
VALLEYS
VARIATIONS