An Investigation of the Resultant Transport Wind Within the Urban Complex

The resultant transport wind speed within the urban mixing layer is compared with the hourly averaged surface wind speed. The mixing depth and resultant transport winds were obtained from twice daily (sunrise and midday) urban soundings released near the center of the city of St. Louis, Mo. The hourly averaged surface wind speeds were recorded at a suburban airport location 13 mi northwest of the sounding release site. A good positive correlation and regression fit on the midday data indicated that the hourly averaged surface wind can not only be used to estimate the resultant transport wind speed, but that the resultant transport wind is a reasonably uniform parameter within the urban complex at that time of day. The morning resultant transport wind speed and surface wind speed do not correlate as well as the midday, especially for the lower wind speed regime. A high positive correlation between the arithmetic average of the observed wind speeds within the mixed layer and the resultant (vector avenge) transport wind speeds within the same layer from over 150 soundings imply that wind direction change with height is not a large factor, especially during the midday sounding period.