Urban heat islands are metropolitan areas that are notably warmer than the areas surrounding them. This extra heat comes from the activity of cities: more cars expelling exhaust, decreased green space, more humans packed into a tight space and emitting body heat. These heat islands can result in poorer air quality, increased formation of ozone, and discomfort and it’s associated negative effects on human mental and physical health. For all of these reasons, minimizing the heat in urban areas through smart infrastructure and well-planned green spaces within cities is becoming a priority for many cities. For example, in the past decade, a Californian Assembly bill required the Cal/EPA develop a definition of Urban Heat Islands (UHI) that could be used to gauge the urban heat on health, emissions, and air pollution.
SIG provided GIS support to Altostratus in a first-of-its-kind project to develop an Urban Heat Island Index for the State of California. The UHI Index is was developed so that the California Environmental Protection Agency (CalEPA), the State, and various city governments have a heat index scale that can be used in a range of applications. For example, some of the more immediate applications included: 1) as an additional layer of information in the CalEnviroScreen 3.0 tool (https://oehha.ca.gov/calenviroscreen), which helps identify communities disproportionately impacted by multiple sources of pollution; 2) as way to pinpoint potential energy savings, air-quality improvements, and GHG emission reductions from urban heat mitigation measures such as through increasing park space, using cooling pavements, or establishing green walls; and 3) as a method of identifying potential public health effects from heat islands and options for alleviating those impacts through better building design and urban planning.
To assist the Cal/EPA in developing a UHI Index for California, Altostratus and SIG created a comprehensive, detailed, multi-scale atmospheric modeling and mapping study that included fine-resolution meteorological and urban-vegetation modeling of urban heat islands. The studies that fed into the UHI Index were developed at city or census-area scales, as appropriate, and selected in consultation with CalEPA. The entire state of California was modeled using mesoscale and meso-urban models, but fine-scale meteorological characterizations and models, were limited to select urban areas. The results were then translated into easily usable information for the CalEPA, city governments, and California regulatory agencies.