Abstract
In urban areas, the human influence on the city-ecosystem often results in a Subsurface Urban Heat Island (SUHI), which can be used geothermally. Unfortunately, a model of a SUHI does not consider the geology and hydrogeology of the subsoil. These can vary significantly over short distances, and are of considerable importance for the energy balance. In this work, we calculated the energy and its density stored in the subsoil via a SUHI. For this so-called energy-SUHI (e-SUHI), we evaluated the geology and its physical parameters for the first 20 m below ground level in the German city of Nuremberg and linked them to measured underground temperatures in a GIS application. This approach revealed stored energy of 1.634 × 1010 MJ within the soil and water for the study area with an area of 163 km2 and a volume of 3.26 × 109 m3. It corresponds to an average energy density of 5.0 MJ/m3. The highest energy density of 16.5 MJ/m3 was found in the city center area and correlated well to increases in subsurface temperature. As expected, our model reacts sensitively to thickness changes in the geological layers and the unsaturated zone.
Highlights
Urban environments shape the thermal regime of their surroundings on various levels. They create an urban climate, which often results in positive temperature anomalies in the atmosphere as an Urban Heat Island UHI [1,2,3]
A similar effect can be observed underground. This is known as a Subsurface Urban Heat Island (SUHI), when soil- and groundwater temperatures are higher than in the surrounding area due to anthropogenic influences
3 for the energy density and 12.3 °C for the groundwater temperature are shown in MJ/m as given in Table 1, there are uncertainties with regard to the specific heat capacity of the Figure 10 as This
Summary
Urban environments shape the thermal regime of their surroundings on various levels.They create an urban climate, which often results in positive temperature anomalies in the atmosphere as an Urban Heat Island UHI [1,2,3]. A similar effect can be observed underground This is known as a Subsurface Urban Heat Island (SUHI), when soil- and groundwater temperatures are higher than in the surrounding area due to anthropogenic influences. For some cities such as Munich, Paris, Winnipeg, Cardiff, and Osaka, spatiotemporal spreads of the SUHI are already well documented. Proportions of vegetation and water surfaces decrease and further reduce cooling effects caused by evapotranspiration This results in further heating of land surface and soil temperatures [17,18,19,20,21]
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