The possible influence of urban surfaces on rainfall development: a sensitivity study in 2D in the meso-gamma-scale

Urban areas can represent a considerable part of the model domain in meso-s cale numerical simulations with typical horizontal domain lengths of 20-200 km. This paper addresses the question of the extent of the influence of ur ban surfaces on the development of convective precipitation in meso-gamma-s cale numerical models. For this purpose, a spatially variable parameterizat ion scheme for surface sensible heat flux, surface latent heat flux, and ro ughness is introduced into a meso-scale numerical model. A sensitivity stud y in 2D is performed to assess the impact of variations of the individual p arameters on the development of precipitation. The results indicate that su rface conditions should not be neglected and can have considerable influenc e on convective rainfall. It appears that within a time frame of 4 h it is particularly the sensible heat flux variations that have the most significa nt impact. (C) 2000 Elsevier Science B.V. All rights reserved.