| The world is undergoing a rapid urbanization process unprecedented in human history: more than half of the global population is now living in urban areas. The associated change of surface landuse types has imposed significant impacts and stresses on environmental systems, prominent examples including heat island formation, modification of the ecohydrological system and degradation of air and water quality. The last few decades have seen increasing efforts to capture and characterize the physics of flow and surface transport processes in the lower urban atmosphere, in order to provide solutions to many urban environmental problems. In this work, we developed a new set of parameterization schemes for surface exchange of energy and water in urban canopies. The new model features: (1) explicit resolution of sub-facet heterogeneity, (2) a spatially-analytical algorithm for computation of urban surface temperatures and soil fluxes, and (3) incorporation of hydrological models for both natural and engineered urban facets. In addition, we analyzed model sensitivity to uncertainties in the parameter space using advanced statistical simulations. Intensive field measurements have also been carried out through a large network of sensors deployed over the campus of Princeton University. Data collected from the sensor network are used to provide input parameters as well as to validate the new exchange schemes. The new model has been tested extensively under ideal and realistic case studies and was shown to be adequate in reproducing a large array of surface parameters, including skin temperatures, net radiation, turbulent fluxes and soil water content. The new model can also be readily extended for practical applications such as assessment of various mitigation strategies of urban heat islands. |
