ESTIMATION OF LAND-SURFACE PARAMETERS IN URBAN BOUNDARY LAYER

Abstract

Land-surface parameters of urbanized terrain are evaluated based on the field measurement data. Following results are obtained;(1) The value of momentum roughness length (Z₀) is 1.56m and it is greater than the heat roughness length (z_T) and water vapor roughness length (Z_q). The ratios kB_T^-1=ln (Z₀/Z_T) and kB_q^-1=ln (Z₀/Z_q) are 8.0 and 20.5 respectively.(2) The value of evaporation efficiency (β) is 0.05-0.2. After precipitation β is significantly decreasing with time for a few weeks. Evaporations from vegetation and concrete material are estimated respectively. Vegetation has a potential to emit latent heat as much as net radiation due to the oasis effect. Concrete material has a potential to cover the β variation range over residential area. When horizontal wind velocity is large, β is decreased.(3) The averaged value of albedo is about 0.13. When there is rainfall, albedo is decreased. But the value is back to about 0.13 within 2-3 days.