DCNet: National Capital Region testbed

Among the many recent assessments of urban meteorology, the 10th Prospectus Development Team of the U.S. Weather Research Program (USWRP) reviewed specialized weather information needs of the diverse user groups and population sectors found in urban and suburban areas. Among its recommendations were demonstration projects, testbeds, in selected cities for high resolution mesoscale analysis. In response to acceptance by the Federal Committee for Meteorological Services and Supporting Research (FCMSSR) of recommendations made by the JAG/SEATD report, a Joint Action Group for Joint Urban Testbeds (JAG/JUTB) has been form to develop an operational concept for joint urban testbeds.

The problem is complex; winds within a city sometimes bear little resemblance to those of the surrounding countryside. The weather forecasting community tends to rely on wind information collected at airports, typically well outside the urban areas that are now of main interest. To assume that the wind fields experienced at airports are the same as those appropriate for downtown areas would clearly be inappropriate. The presence of buildings and the “street canyons” separating them cause behaviors that are almost random, exceedingly difficult to predict or even describe. However the flow above the “urban canopy” is far more describable in terms of larger scale meteorology. It is convenient to think in terms of two regimes – the street canyon flows beneath the urban canopy and the “skimming flow” above it. Washington, D.C., presents an excellent testbed for studies, because the urban canopy is well defined by the height constraint on the buildings.

Since 2003, NOAA/ARL has been operating a prototype testbed for Washington, DC. There are thus two major reasons to focus attention on the Washington, D.C., metropolitan area. First, the attention is needed because, like it or not, Washington, DC is a potential terrorist target. Second, the urban landscape lends itself to the application of new science, so that greatly improved capabilities are feasible. Currently, there are 11 NOAA/ARL urban turbulence monitoring stations in operation within the National Capital Region Testbed. Additional stations are scheduled for installation this year which will complete the NOAA/ARL turbulence network for the National Capital region. The completed turbulence monitoring network will provide intensive coverage of the District's Federal Triangle area with surrounding coverage at an approximate 5 km resolution.