Sensitivity Testing of an Urban Surface Scheme Coupled to a 1-D Boundary Layer Model

A 1-D boundary-layer model (Troen and Mahrt 1986) that treats both local and non-local mixing is coupled with an urban surface scheme (Masson 2000) and a 5-band longwave cooling scheme (Roach and Slingo 1979) in order to efficiently simulate urban-atmosphere interactions. The 1-D nature of the model limits its application to relatively horizontally homogeneous scenarios. A simple soil-vegetation surface scheme is included to model urban vegetated areas. Overall, modelled surface energy balance fluxes agree well with measurements made at the Sperrstrasse tower site (16% vegetation) in Basel from May 30-31, 2002 during the BUBBLE campaign. Relaxation-type advection from a simulated column with a soil-vegetation (e.g. rural) surface scheme to the urban column is implemented to explore the impact of advection. A variety of surface scheme sensitivity experiments are conducted, both with and without coupling between the surface scheme and the boundary layer model. Results are discussed with particular attention to the impact of model coupling on sensitivities of daytime peak net radiation, surface heat flux partitioning, and canyon air temperature.