Data from the NOAA BAO (Boulder Atmospheric Observatory) tower and the PROFS (Program for Regional Observing and Forecasting Services) surface mesonetwork have been used to detect the meso- and microscale flow patterns associated with the passage of a shallow cold front over complex terrain. This front moved across the PROFS surface mesonetwork and the BAO tower site on the morning of the 3 December 1981. Partial blocking of the cold airflow by the higher terrain to the north led to a westward movement of the cold front in the upper reaches of the South Platte River drainage basin. A meso-beta-scale anticyclonic eddy subsequently formed in the lee of this terrain obstruction.
The micro-alpha-scale vertical eddy structure in the cold frontal zone is defined using data from the BAO tower. Updrafts of >6 m s-1 at 200 m AGL occurred at the wind-shift and temperature-drop line. Immediately behind this feature, micro-alpha-scale eddies entrained air through the frontal surface, diluting the low-level flow, which was overtaking the front from behind. These feature have been observed by others in atmospheric and laboratory gravity currents.
Young, G. & Johnson, R. (1984).
Department of Atmospheric Science, Colorado State University, Fort Collins.