In face of climate change and urbanization, the need for thermally comfortable outdoor urban spaces is increasing. In the design of the thermally comfortable urban spaces and decision making about interventions that enhance thermal comfort, scientists and professionals that work for cities use meteorological measurements and models. These measurements can be done by professional and accurate meteorological sensors, but also by simpler mobile instruments such as the easy-to-use Kestrel weather meters. In using these simple type of sensors, it is important to know what the performance of these sensors is for outdoor thermal comfort assessments and how they can be used by scientists and professionals in decision making about urban designs that enhance thermal comfort.To answer these questions, we carried out three experiments in the summer of 2020 in Amsterdam, in which we tested the 11 Kestrel 5400 heat stress sensors and assessed the performance of this equipment for thermal comfort studies. We concluded that Kestrel sensors can be used very well for assessing differences in air temperature and PET (Physiological Equivalent Temperature) between outdoor built environments. For both air temperature and PET, the RMSE between the 11 Kestrel sensors was 0.5 °C maximum when measuring the same conditions. However, Kestrel sensors that were placed in the sun without a wind vane mounted to the equipment showed large radiation errors. In this case, temperature differences up to 3.4 °C were observed compared to Kestrels that were shaded. The effect of a higher air temperature on the PET calculation is, however, surprisingly small. A sensitivity analysis showed that an increase of 3 °C in the air temperature results in a maximal PET reduction of 0.5 °C. We concluded that Kestrel sensors can very well be used for assessing differences between air temperatures and PET between two locations and assessing the thermal effects of urban designs, but care should be taken when air temperature measurements are carried out in the sun. We always recommend using the wind vanes to deviate from high radiant input orientations for the temperature sensor, and placing the stations next to each other at the beginning and at the end of the measurements to check whether the stations actually measure the same values. Any differences can be corrected afterwards.
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This report summarizes the result of the comparison between 4 weather stations: 2 Kestrels 5400 Heat Stress and 2 Davis Vantage Pro2. The measurements were performed from the 08/04/2019 to 11/04/2019 on the rooftop of the Benno Premselahuis from the Hogeschool van Amsterdam.
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The thermal walk investigates the influence of urban design on the thermal experience of pedestrians moving through a certain urban area. Thermal walks are often used by scientists to understand how residents experience heat in urban environments. However, thermal walks can also be beneficial to urban professionals working at local governments that need to adapt urban areas to rising temperatures. Thermal walks can answer their questions such as: How hot is a shopping street, a residential area, a specific walking route through the city or a station area? Which adjustments are needed to create cool spaces? Which factors determine whether the outdoor space is hot or cool and which of these factors can be included in a heat-resilient design? A thermal walk reveals and lets participants experience which urban designs are hottest, coolest or most pleasant, and which factors play a role. Therefore, thermal walks can help urban professionals by:• Mapping the heat resilience of a specific area and understanding which adjustments can help to create cooler areas; and• Teaching them the phenomenon of urban heat and the factors that lead to a heat resilient design. On the 18th of June 2019, during the ‘We make the city’ festival, we used the thermal walk to investigate the heat resilience of the walking route on a former historic naval base in the city of Amsterdam, the Marineterrein. In addition, the thermal walk was accompanied by mini-lectures in order to teach the participants about the phenomenon of urban heat.
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Hoe richten we de stad koel en hittebestendig in? Stadsontwerpers proberen daar vaak vanachter hun bureau oplossingen voor te bedenken op basis van kaarten, schetsen en berekeningen. Daar kan nu de 'thermal walk' aan worden toegevoegd: zelf al wandelend hitte meten en ervaren.
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As a consequence of climate change and urbanization, many cities will have to deal with more flooding and extreme heat stress. This paper presents a framework to maximize the effectiveness of Nature-Based Solutions (NBS) for flood risk reduction and thermal comfort enhancement. The framework involves an assessment of hazards with the use of models and field measurements. It also detects suitable implementation sites for NBS and quantifies their effectiveness for thermal comfort enhancement and flood risk reduction. The framework was applied in a densely urbanized study area, for which different small-scale urban NBS and their potential locations for implementation were assessed. The overall results show that the most effective performance in terms of flood mitigation and thermal comfort enhancement is likely achieved by applying a range of different measures at different locations. Therefore, the work presented here shows the potential of the framework to achieve an effective combination of measures and their locations, which was demonstrated on the case of the Sukhumvit area in Bangkok (Thailand). This can be particularly suitable for assessing and planning flood mitigation measures in combination with heat stress reduction.
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Het tegengaan van hittestress is een van de grote uitdagingen bij het leefbaar houden van de stad. Door klimaatverandering neemt het aantal extreem warme dagen toe. Daarnaast is het in de stad doorgaans warmer dan in de omringende rurale gebieden, het zogenaamde hitte-eiland-effect. Hoge temperaturen leiden tot hitte-stress bij mensen, met negatieve gevolgen voor de gezondheid, met name van kwetsbare groepen. Dagen met een aanzienlijke kans op hittestress komen in ons land meermaals per jaar voor, zeker in stedelijk gebied. Het aantal dagen met hittestress en de intensiteit van de hitte zal in de toekomst verder toenemen. Klimaatadaptatie van het stedelijk gebied is daarom een noodzaak geworden.Groen is een zeer effectief middel om de stad meer klimaatbestendig te maken. Het effect van groen is echter afhankelijk van het type groen en de omgeving waarin dat groen staat. Concrete richtlijnen voor effectief groen in verschillende wijktypen ontbreken tot nog toe.
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Built environments are increasingly vulnerable to the impacts of climate change. Most European towns and cities have developed horizontally over time but are currently in the process of further densification. High-rise developments are being built within city boundaries at an unprecedented rate to accommodate a growing urban population. This densification contributes to the Urban Heat Island phenomenon and can increase the frequency and duration of extreme heat events locally. These new build-up areas, in common with historic city centres, consist mainly of solid surfaces often lacking open green urban spaces.The Intervention Catalogue is the third publication in a series produced by the Cool Towns project and has been designed as a resource for decision makers, urban planners, landscape architects, environmental consultants, elected members and anyone else considering how to mitigate heat stress and increase thermal comfort in urban areas. Technical information on the effectiveness of the full array of intervention types from trees to water features, shading sails to green walls, has been assessed for their heat stress mitigation properties, expressed in Physiological Equivalent Temperature (PET). The results shown in factsheets will help the process of making an informed, evidence based, choice so that the most appropriate intervention for the specific spatial situation can be identified.
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