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Published on: December 12, 2025
Subsurface urban heat islands in German cities
Kathrin Menberg1, Peter Bayer, Kai Zosseder
1Karlsruhe Institute of Technology (KIT), Institute for Applied Geosciences (AGW), Kaiserstr. 12, 76131 Karlsruhe, Germany. kathrin.menberg@kit.edu
The Science of the Total Environment
|November 27, 2012
Summary
Subsurface urban heat islands (UHI) cause significant groundwater heating, with hotspots up to +20K from local sources. This study introduces a new UHI intensity indicator, revealing pronounced shallow subsurface warming compared to atmospheric UHI.
Area of Science:
- Geosciences
- Environmental Science
- Urban Climatology
Background:
- Subsurface urban heat islands (UHI) and their driving factors remain poorly understood.
- Limited data exists on the intensity and spatial extent of underground thermal anomalies in cities.
Purpose of the Study:
- To compare groundwater temperatures in shallow aquifers beneath six German cities.
- To identify and analyze the drivers of subsurface UHI.
- To introduce a new metric for quantifying large-scale UHI intensity.
Main Methods:
- Comparative analysis of groundwater temperatures in shallow aquifers across six German cities.
- Isotherm mapping to visualize regional temperature distributions.
- Introduction and application of the 10-90%-quantile range urban heat island intensity (UHII(10-90)) indicator.
Main Results:
- Identified localized hotspots of groundwater temperature increase up to +20K, linked to specific heat sources like power plants and landfills.
- Observed concentric temperature patterns with peak heating in city centers, indicating long-term thermal energy accumulation.
- Demonstrated that the UHII(10-90) reveals more pronounced shallow subsurface warming than atmospheric UHI.
Conclusions:
- Subsurface UHI significantly impact groundwater temperatures, driven by both local heat sources and cumulative long-term effects.
- The UHII(10-90) is an effective indicator for quantifying and comparing large-scale subsurface UHI intensity.
- Understanding subsurface thermal anomalies is crucial for urban planning and resource management.
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