Flow patterns at the ends of a street canyon: Measurements from the Joint Urban 2003 field experiment

As part of the Joint Urban 2003 tracer field experiment held in Oklahoma City, a relatively high concentration of wind sensor equipment was deployed in a street canyon within a one block section on Park Avenue during intensive operation periods (IOP's). The ground-level wind sensors at each end of the street near the intersection often showed winds on average flowing in opposite directions on the north and south sides of the street, perhaps indicative of a horizontally rotating corner vortex (Brown et al., 2004). In this paper, we further investigate the flow patterns at the street canyon ends by looking at both the sonic anemometers placed near ground level and tethersonde systems operated in “ladder” mode that were suspended over the sides of the buildings on each side of the street. The measurements show that this vortex-like flow regime occasionally existed through the entire depth of the street canyon. We found that this vortex flow pattern only appeared for a specific range of upper-level wind directions and then changed to purely channel flow for other wind directions. We found that the depth through which the vortex flow existed varied with the upper-level wind direction. In the presentation, we will briefly describe the street canyon experiment and show plots of the wind flow patterns as a function of upper-level wind direction. We will discuss whether these results are unique to this street canyon or whether they could be applied to other street canyons.