Abstract: As part of NOAA's UrbaNet program a research network of roof-mounted micrometeorological towers has operated in Washington, DC for several years. Recently, high frequency measurements of the three wind components and temperature were taken at two locations, 10 m above roof level, for several months each. The spectral characteristics of the turbulent flow immediately above the rooftops (and well within the roughness sublayer) are examined, and relationships to turbulent flow behavior above the roughness sublayer are discussed.