Temperature inversion buildup in valleys of the Rocky Mountains

Conference · Mon Jun 01 04:00:00 EDT 1981

OSTI ID:5738544

Whiteman, C D

The characteristics of nocturnal temperature inversions and local wind systems in the valleys of Western Colorado were determined from tethered balloon data. Data for the study come from a series of field experiments conducted in seven Colorado valleys in 1975, 1977, and 1978. To date, analyses of the data have been confined primarily to the study of the breakup of valley temperature inversions. In the present study attention is focused on the smaller quantity of data on the formation and development of temperature inversions and on local wind systems. Results indicate that during periods of clear undisturbed weather, temperature inversions begin to form an hour or two before sunset in the deep Western Colorado valleys studied. The initiation of the inversions at the valley floors begins with the drainage of cold air off the shaded hillsides. A stage of rapid inversion growth follows in the several hours after sunset as inversions grow in depth at rates of 170 to 210 m h/sup -1/. During this stage of growth, down-valley winds become established within the inversion and increase in depth and speed. Transport of mass in the downslope flows over the sidewalls above the inversion top is thought to play a major role in causing the growth in depth of the inversions. Calculations of energy loss from the valley atmosphere show that the strongest cooling rates during this period occur just below the ascending inversion top. Following the period of rapid inversion growth, a final stage of inversion buildup ensues. This stage, which begins before midnight and lasts until sunrise, is characterized by a continued slow growth of the inversion top, weak further development of the down-valley wind system, and a rather uniform weak rate of cooling through the valley volume. By sunrise, inversions have typically grown to the full depth (300 to 800 m) of the valleys studied, attaining potential temperature gradients of 22 to 33/sup 0/K km/sup -1/.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 5738544
• Report Number(s): PNL-SA-9357; CONF-811104-8; ON: DE82005922
• Country of Publication: United States
• Language: English

Related Subjects

500100* -- Environment
Atmospheric-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
DATA
DATA ACQUISITION
EXPERIMENTAL DATA
INFORMATION
MONITORING
MOUNTAINS
NUMERICAL DATA
ROCKY MOUNTAINS
TEMPERATURE INVERSIONS
VALLEYS
WEATHER
WIND