The Tokyo-98 Urban Turbulence Experiment

This paper describes a comprehensive field project of atmospheric turbulence and surface temperature carried out in the fall of 1998 in Tokyo, Japan. Presented are the design of the measurements and preliminary results. The experiment presented hereafter differs in many aspects from similar turbulence work. Unlike many other studies which chose low-density suburban areas as their main site, a densely-built residential neighbourhood with little greenspace, typical of many Japanese residential areas, was selected. For the first time a single-boom construction-type crane was employed as the instrument platform. Because of its mobility it can be installed at the site which offers the best possible fetch conditions regardless of restrictions usually found in similar urban work. Besides traditional turbulence instrumentation the present study includes for the first time in an urban environment instrumentation to measure spatially averaged sensible heat and momentum fluxes. A second crane was equipped with identical instrumentation and positioned at a lower height (but probably still within the roughness sublayer) to obtain information about the height variability of turbulence characteristics. Observations of surface temperatures using a variety of remote sensors were taken during most of the measurement period and profiles of mean standard atmospheric variables throughout the boundary layer are available for a few days.

The following results will be presented: i) Surface morphology of site; ii) A new method to determine the zero-plane displacement length, based on simultaneous scintillometer data from two levels; iii) Non-dimensional TKE dissipation rates and comparison with relatively new data from the homogeneous surface layer; iv) Comparison of area-averaged and point measurements of sensible heat fluxes; v) Preliminary results of remotely-sensed surface temperatures.