Impact of Heat Waves on Urban Areas in the North Eastern United States

Abstract:

We utilize high-resolution numerical simulations to understand the interaction between heat waves and urban heat islands in the North Eastern United States. Urban areas, due to their dense built-surface cover that efficiently stores and dissipate heat and reduced evapotranspiration, experience elevated near surface temperatures compared to surrounding rural areas. This difference between urban and nearby rural temperature is commonly known as the Urban Heat island Intensity (UHI), which amplifies the effects of heat waves in cities. In this work, the Weather Research and Forecasting (WRF) model is significantly modified in two major ways to study two heat wave episodes in the North East during the Summer of 2006. First, the single layer urban canopy model in WRF is replaced by the Princeton Urban Canopy Model (PUCM), which includes representation for sub-facet scale heterogeneity. Second, the dominant land use approach used in the default land surface scheme is substituted with a tile-based approach to suitably capture the variability in the urban surface cover. Our preliminary results show that the magnitude of the UHI increased in New York City by more than 1°C during both the nighttime and daytime periods during the heat wave episodes. In Baltimore and Washington D. C, while the UHI increased during the nighttime period, the daytime UHI was mostly unchanged. This ongoing work will further focus on the role played by moisture availability, available energy, wind direction and magnitude and urban characteristics like population density and urban cover in modulating the UHI during these intense heat wave periods.