Assessment of Localized and City-Specific Urban Heating in Four North-Eastern Cities Using Spatial Synoptic Classification

The urban heat island (UHI) is a well-documented phenomenon that occurs when temperatures within an urban area are greater than that of the surrounding rural area. This is due to increased sensible heat storage, anthropogenic heating, and many other factors. There have been many studies completed on understanding city-specific UHIs, yet there has been minimal research conducted on how different synoptic air masses modify the intensity of the localized UHI within the canopy layer. Increased temperatures in urban areas have been associated with a negative impact on human health by elevating personal mortality risk, exacerbating already harmful heat waves, and not allowing relief from daytime heat with higher overnight temperatures; hence, it is important to study the spatiotemporal variations in the surface UHI. For cities to manage the growing risks and vulnerability of such exposures, progress in understanding the spatial and temporal variations in the development of UHIs is critical.

The current study will use the comprehensive Spatial Synoptic Classification System (SSC) as a means to account for daily air mass type. The objectives of this project are first to study the development of the UHI, and differences in its intensity, under the seven synoptic air masses using data from more than 300 UrbaNet stations (NOAA and Earth Networks) in four northeastern cities: Philadelphia, New York, Boston, and Baltimore. Data from 2006 through 2013 during the months of May-September is used with each station collecting 27 meteorological variables at 5-min or 1-hour intervals, providing a very high temporal and spatial resolution for urban analysis. Second, we address the intra-city heterogeneous variation in UrbaNet's high frequency observations and account for local urban fabrics. This is important as temperatures across a city can vary by as many as 4^oC due to different land cover types such as urban parks, asphalt, and white roofs. However, most UHI studies only use two stations to determine UHI intensity, which does not account for this variation in surface types. Inter-city comparisons will be made as well as comparisons between the cities themselves, to help understand localized UHIs. Understanding which regions of each city have the strongest warming potential can aid mitigation strategies in affected areas and help address urban risks and hazards to extreme heat. Further, the knowledge of which air mass type results in the most intense UHI can aid operational meteorologists and public health officials to issue targeted heat warnings when an oppressive air mass is forecasted to arrive.