Universität zu Köln

Eingrüber, Nils ORCID: 0000-0003-1329-2236 (2026). Investigation and comparison of heat mitigation potentials of climate change adaptation measures in urban areas between Cologne/Germany and Pune/India using the urban microclimate simulation model ENVI-met. PhD thesis, Universität zu Köln.

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Abstract

Many urban areas around the world are characterized by both a growing population and an intensification of the urban heat island effect in the context of climate change. The increasing heat exposition of urban dwellers causes significant health risks, not only expressed by higher mortality rates, but also by economic damages. Climate change adaptation strategies are therefore needed in urban design to reduce heat loads and improve thermal outdoor comfort. Cooling potentials of different heat stress mitigation measures must be evaluated based on sound-scientific analyses to identify and recommend best performing options for urban planners. Heat mitigation potentials of technical- and nature-based solutions vary, also between cities depending on the climatic and hydrological conditions, urban geometry and structure as well as cultural differences. High-resolution microclimate modelling and scenario analyses are a promising approach to evaluate thermal effects of various adaptation measures in urban areas during heat events. The physically-based 3D-gridded ENVI-met model is used to compare the microclimatic effects of climate change adaptation measures between a humid mid-latitude urban area in Cologne/Germany and a semiarid tropical urban area in Pune/India exposed by pronounced monsoon conditions. The models are parameterized and driven based on field measurements in the study areas and remote sensing data. Model outputs are validated using densely-distributed microclimate sensor networks installed within the study areas for different heat periods also including an extreme 20-year heat event. The quality-controlled, standardized and calibrated citizen science sensor networks with around 60 NETATMO sensors as well as research-grade reference stations within each of the two heterogeneous urban study areas (16 ha) represent a novelty and combine the scientific requirement of high resolution and accuracy with the participation and activation of citizens needed for later implementation of climate change adaptation measures. A mean Nash-Sutcliffe model efficiency coefficient of 0.9 and up to 0.98 for simulated air temperature indicates a high statistical goodness-of-fit of the model to sensor measurements, proving the model reliability for scenario analyses. 92 different scenarios implementing adaptation measures like facade or roof greenings, wet roofs, cooling building materials, street trees, greened front gardens, grass grid paver unsealings, reflective ground surfaces, sunsail shadings or nozzle water spray systems are developed and simulated. Scenarios also take into account future climate change projections. To our knowledge, such a holistic toolset of scenarios including combinations of different measures and different degrees of implementation was never compared in previous research. Simulated air temperature and physiological equivalent temperature (PET) of the scenarios are compared to the status-quo reference to quantify cooling potentials. Heat mitigation effects are checked for statistical significance and compared between both study areas to investigate which measures perform best under the given climatic conditions. While significant mean air temperature differences of -1.6 K were observed for Cologne, cooling effects are mainly smaller in Pune with mean air temperature differences of only -1.2 K. For PET, heat mitigation potentials are also smaller in Pune with mean differences of -1.6 K, while mean cooling effects of -2.9 K were found for Cologne. These effects are in a magnitude to compensate expected global warming until the end of the century. While technical solutions such as white surfaces mostly perform better in Pune for air temperature, nature-based solutions mainly have a better heat mitigation potential in Cologne. This can be attributed to higher radiative forcing, limited water availability as well as reduced ventilation in India. PET cooling effects are smaller in Pune than in Cologne for nearly all technical- and nature-based solutions. Overall, higher cooling effects were observed for combinations of different solutions than for single measures. More realistic implementations like 25% greened buildings still have a high potential for heat mitigation in the entire quarter. Reflective surfaces and sunsails do not significantly improve thermal outdoor comfort. This study implies that careful parameterization of urban microclimate models based on quality-controlled field measurements is essential for a high model accuracy. Densely-distributed sensor networks using a citizen science approach can support scientific applications as well as activate stakeholders to implement adaptation measures. Findings have important implications for strategical decision-making in urban planning and highlight the relevance of local assessment of adaptation pathways taking into account urban characteristics and environmental conditions. The identification of best-performing measures ensures human wellbeing in a changing climate and supports several Sustainable Development Goals of the United Nations.

Item Type:	Thesis (PhD thesis)
Translated title:	Title Language Untersuchung des Hitzemitigationspotentials von Klimawandelanpassungsmaßnahmen in städtischen Räumen im Vergleich zwischen Köln/Deutschland und Pune/Indien mit Hilfe des urbanen Mikroklima-Simulationsmodells ENVI-met German
Creators:	Creators Email ORCID ORCID Put Code Eingrüber, Nils nils.eingrueber@t-online.de https://orcid.org/0000-0003-1329-2236 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-796523
Date:	2026
Place of Publication:	Köln
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Geographisches Institut
Subjects:	Earth sciences Geography and travel
Uncontrolled Keywords:	Keywords Language Climate change adaptation English Heat mitigation by technical- and nature-based solutions English High-resolution urban microclimate modelling English Citizen science English
Date of oral exam:	12 March 2026
Referee:	Name Academic Title Schneider, Karl Prof. Dr. Bogner, Christina Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/79652