Reducing the Urban Heat Island Effect In Copenhagen

Abstract

The urban heat Island effect is a well-known phenomenon that has been documented and studied in many urban areas. Put simply, an urban heat island effect occurs when a city is generally warmer than its surrounding hinterland, which tends to be less developed. Generally speaking, the urban heat island effect is the result of added solid surface horizontal and vertical geometry to a landscape that tends to trap solar radiation as heat. In 2010, an urban heat island effect was documented in Copenhagen, Qenmark by researchers from the University of Copenhagen. The researchers also discovered that the urban heat island effect in Copenhagen was not uniformly distributed; that is, some streets and neighborhoods were hotter than others. The present study, undertaken as a professional project for the completion of the masters of urban planning degree from the University of Washington, attempts to explain what factors contribute to intra-urban temperature variation within Copenhagen. Climatic and urban form variables known to interact with urban heat island effect were identified and, to the extent possible given available data, were modeled in a GIS-based spatial statistics analysis. The modeling exercise returned results indicating a statistically significant relationship between the Normalized Difference Vegetation Index levels of a ISO-meter buffer area surrounding the urban canyons and intra·urban air temperature variation amongst the canyons. The urban heat island effect presents a health concern within Copenhagen urban canyons during summer heat waves, when a population unaccustomed to high temperatures becomes susceptible to heat exhaustion and heat stroke with particular risk posed to the very young and old. As such, the present study evaluated the potential for green infrastructure elements to provide cooling to Copenhagen's commercial/residential urban canyons during the summer months. A literature search was conducted to evaluate the potential for green roofs, street trees, and urban parks to provide cooling available for horizontal transfer to urban canyons from a ISO-meter buffer area surrounding the canyons. Given that cooling is not desired in Copenhagen at any time of the year other than the summer months, cooling generated via evapotranspiration by vegetation inherent to green infrastructure is a logical solution as evapotranspiration peaks in intensity during the summer growing months. Ah:hough quantitative temperature reduction predictions could not be made, recommendations for more comprehensive modeling research are included herein along with a general discussion of design principles relevant to green infrastructure design interventions intended to provide cooling to urban canyons.