Scalar Roughness Parameters for a Suburban Area

Abstract

This paper describes land-surface parameters, including the roughness lengths of momentum, heat, and water vapor, and the surface moisture availability derived from 1 year of field measurements at a suburban site in Tokyo, Japan. The main results are as follows. The estimated ratio of roughness length of momentum to heat, kB -1 T , had an average value of 7. This value of kB -1 T was larger than those documented for vegetated and agricultural surfaces, but less than that reported for a light industrial area. In winter, kB -1 T tended to be smaller, suggesting dependence on the vertical position of the heat source within the canopy. The kB -1 T results also showed a diurnal change, in which higher values occurred in the afternoon. The parameter kB -1 q , the ratio of the roughness length of momentum to water vapor, ranged from 40 to 600. The parameter kB -1 q depended on the water vapor deficit, the friction velocity, and the number of elapsed days after precipitation, all of which can change surface water availability. The value of surface moisture availability, β, ranged from 0.02 to 0.3. β gradually decreased with the number of elapsed days after precipitation.