Eighth Symposium on the Urban Environment
Boundary Layers and Turbulence Committee
Special Symposium on Measurements in the Urban Environment and Observations


On the rooftop micrometeorology and heat islands of Washington and New York City

William R. Pendergrass, NOAA/ARL/ATDD, Oak Ridge, TN; and B. B. Hicks and C. A. Vogel

A research network of roof-mounted micrometeorological towers has operated in Washington and New York City for several years. This network (“DCNet”) yields fifteen-minute averages of temperature and wind components, and of all of the associated variances and covariances. Although individual 15-minute averages are highly scattered, their averages yield a number of relationships that help describe the surface turbulence regimes and the micrometeorological characteristics of the surroundings of the towers, with directional effects being clearly evident. The nocturnal heat island effect is strikingly evident in the w'T' covariance data from many stations. In general, every 1 C elevation of temperature within the Washington heat island appears to be associated with a sensible heat flux increase of 30 to 40 W/m2. Average diurnal cycles of the w'T' covariance show the influence of both the heating of buildings in winter and the cooling of them in winter. This is displayed with sufficient detail to see the consequences of increased heating/cooling activity in the few hours before the start of the work day, in preparation for the arrival of the workforce. Most of the detail of this kind results from consideration of seven stations distributed across the Washington, DC, region, with data obtained in areas with the oldest and largest buildings yielding the strongest signals. There are only two stations providing relevant observations in New York City, but these both yield strongly supporting results. These results reveal the influence of the surroundings, with large scatter being characteristic of sites with the greatest local surface inhomogeneity

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Joint Session 16, Boundary Layer and Turbulence Measurements in the Urban Environment
Wednesday, 14 January 2009, 8:30 AM-10:00 AM, Room 124A

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