National temperature map shows how hot it ‘feels’ on summer’s day

The climate is changing and heatwaves are becoming more frequent. This has significant consequences for people’s health, including heat stress, heat-related illnesses and premature death. A temperature map helps identify hotspots, showing how hot it ‘feels’ throughout the Netherlands on a hot summer’s day.

As part of the Delta Plan for Spatial Adaptation, government agencies agreed to employ a stress test to identify hotspots in the Netherlands. As a follow-up to this, the Ministry of Infrastructure and Water Management elected to develop a map which displays ‘feels-like’ temperatures for the whole of the country. Unlike air temperature, the ‘feels-like’ temperature is a good indicator for heat stress and can be employed in discussions on spatial adaptation. For these reasons, Witteveen+Bos created the national temperature map.

The map displays the temperature at a local level within the Netherlands in terms of how hot it ‘feels’ on a hot summer’s day. This ‘feels-like’ temperature is also known as the physiological equivalent temperature (PET). Wageningen University & Research validated the map once it had been created and it has been published on, making it available for everyone. Also available at this site are maps which give an impression of the increased threat of flooding, drought and heat as a result of climate change.

Verification of the method

Wageningen University & Research developed the method for the standardised PET temperature map. The complex method provided room for interpretation, which had a major impact on the temperature map. One of the biggest challenges in the project was ensuring that the algorithm was clear and unambiguous. In close collaboration with Wageningen University & Research in developing the map - and by determining the best method to be employed - a reproducible and high-quality temperature map was developed.

Calculation for the whole of the Netherlands

Calculating the PET temperature per square metre throughout the Netherlands was a challenge, owing to the volume of data collected for this purpose and the calculation capacity required. We optimised the calculation method to accelerate calculations and used our calculation cluster to enable parallel calculations.

Validating the results

The calculation method for the PET temperature map was initially validated using measurement data in Wageningen. To guarantee the map’s quality, Wageningen University & Research also validated the map in Amsterdam, Rotterdam and other locations within the Netherlands. This helped improve the calculation method - for example, the calculation of wind reduction. As a consequence, extremely reliable results are produced. If you would like to know more about this, please visit Chilling out in Amsterdam.

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