Analysis of Nighttime Drainage Winds in Boulder, Colorado during 1980

Abstract

Characteristics of nighttime drainage winds that occurred along the eastern slope of the Rocky Mountains around Boulder, Colorado during the calendar year 1980 are examined. The data used for this study were acquired from the Boulder Wind Network (BWN) and from the Boulder Atmospheric Observatory (BAO). Data were available almost continuously from BWN and less frequently from BAO. BAO is a 300 m tower, instrumented at eight levels, but only surface wind observations are obtained from BWN. However, the combination of BWM and BAO observations represents a relatively unique set of wind data for the examination of drainage flows. Criteria for the identification of drainage winds are used to isolate events that are relatively free from external influences. Eighteen drainage wind events are identified, and some climatological features of the wind regime are established. In addition, the vertical structure of the flow associated with one event that reached the tower is examined in detail. Descriptions of the features of this flow and physical interpretations are presented. It is concluded, on the basis of this analysis, that observed features may be interpreted on the basis of the physical features contained in the model of Rao and Snodgrass (1981).