Urban Dispersion Program: Urban measurements applied to emergency response

Air motions in and around cities are highly complex, and the increasing threat of harmful releases into urban atmospheres makes advancing the state-of-science of understanding and modeling atmospheric flows and dispersion in and around cities essential. The four-year Urban Dispersion Program (UDP) funded primarily by the U.S. Department of Homeland Security and the Defense Threat Reduction Agency has recently been completed. The program's primary focus was to conduct tracer and meteorological field studies in Manhattan to improve our understanding of flow and dispersion of airborne contaminants through and around the deep street canyons of New York City, including outdoor-indoor-subway exchange mechanisms. Additionally, urban dispersion models are being validated and first-responder guidance are being refined using data collected during the two UDP field studies.

Pacific Northwest National Laboratory led several government laboratories, universities and private companies in conducting the two UDP field studies. The first study was a small-scale study that investigated dispersion in the immediate vicinity of the Madison Square Garden during March 2005 (MSG05), while the second UDP study was an extensive study conducted during August 2005 in Midtown Manhattan (MID05).

A brief overview of the UDP field studies will be given followed by a discussion of some limitations of current urban models in simulating dispersion in urban areas. Some first-responder guidance based on findings from recent urban field studies will also be presented.

(PNNL-SA-55605)