Numerical Simulations of Sea Breeze Circulations and Urban Heat Islands in NYC with a High Resolution Urban-Mesoscale Model (uWRF)

The Weather Research and Forecasting (WRF) model, coupled with a multi-layer urban canopy model, is used to evaluate impacts of the urban canopy on sea breeze circulations and urban heat island (UHI) evolution in New York City (NYC). The urban canopy model considers thermal effects, such as heat fluxes from roofs, streets, and walls, as well as the reflection and radiation exchange in street canyons. Mechanical effects of the canopy, such as the turbulent momentum sink by friction are also included. High resolution (1 km.) urban canopy parameters (UCPs) from the National Urban Database were employed to initialize this multi-layer urban parameterization. Three urban classes based on the values of Building Plan Area Fraction were defined. Numerical simulations were validated by use of several sources of information. Data from a dense network of surface weather stations, wind profilers located at building roof tops, and Lidar measurements are compared to model outputs for cases of UHI formation over Manhattan. Thermal and drag effects of buildings represented in the multilayer urban canopy model improve the simulations over urban regions, giving better estimates of the boundary layer, surface temperatures, and wind speeds. Urban canopy effects on precipitation are also analyzed for the cases investigated.