Lund prepares to cope with extreme heat
Extreme weather such as hot summer days and periods of torrential rain have shown that it is necessary for society to make adaptations to the climate. Lund Municipality made a Rainfall mapping 2015/16 and are now also done with a heat mapping. The heat mapping shows which areas and activities are particularly vulnerable. In high heat, the risk groups for heat stress are mainly young children, the elderly and people with underlying diseases or certain forms of functional impairment, and it has been a goal to map the risks in environments where these groups are staying in order to be able to see what measures are needed.
The municipality of Lund has previously measured air temperature and humidity in various places in Lund, but in order to give a more fair view of how the heat is experienced, radiation temperature is also analyzed. The perceived temperature can vary widely between locations where the measured air temperature is similar. The experience depends, among other things, on how sunny a place is and on the surrounding buildings, where the presence of hard and reflective surfaces, tall houses and a lack of shading greenery can produce radiant temperatures of around 30 degrees more than the air temperature. In order to get a comprehensive picture of the heat problem, risks associated with high temperatures both during the day and at night have been studied.
- A few years ago we started by investigating how we could measure the heat in our urban areas, says Adam Wadsten of the Sustainable Growth department, Lund Municipality. We started by looking at satellite measurements and measuring with temperature sensors, and temperature sensors were then tested in The SOM Project. With the help of the sensors, we saw that there were greater differences in air temperatures in Lund than we thought — sometimes up to five degrees. However, both of these methods have their weaknesses and we decided instead to do modelling that other municipalities have also tested, while we also wanted to look specifically at vulnerable objects.
The project was started in 2021 as a collaboration between the municipal office, the service administration and the city building office, who together want to create an in-depth knowledge of the heating situation in Lund's urban areas. Among other things, the insights will be recorded in the revision of Lund's master plan, in the municipality's work on climate adaptation, in a vulnerability analysis for the municipality's sensitive activities and for the planning of the municipality's various activities, for example in the technical administration and school administration. In 2023, the mapping has been completed and three scenarios have been based on — a hot day (25 degrees), a day with extreme heat (31 degrees) and a future day with an extreme value (35 degrees). For each scenario, modelling was also done for three different times of day.
The maps show the Maximum Radiation Temperature (Extreme Value) or average between either 5 am — 8 pm (Daily Average) or 9 am — 4 pm (Heat Stress Risk Map). The color scheme highlights which places in the city can be perceived as very warm in relation to other places. Places that get particularly hot are generally characterized by very direct solar radiation, warm ground surfaces, and proximity to buildings that reflect and emit radiation. Cool locations occur primarily where vegetation or buildings lower radiation temperature through shading. Even green spaces and water help lower the radiation temperature.
The project has also carried out a vulnerability analysis with risk classification of vulnerable objects. Vulnerable objects include school and preschool, nursing home and senior care, social psychiatric accommodation, health centre, playground and swimming area. The objects have been divided into four risk groups, where it turns out that 12% of nursing homes and senior activities fall into the more vulnerable group, as do 24% of playgrounds and 25% of bathing areas. For schools and kindergartens and their farms, the corresponding figure ends up at 3 to 5%.
In mapping the areas at risk of elevated nighttime temperatures, the project observed that the contiguous areas with the highest risk are generally mainly industrial areas, that the middle category areas consist of relatively dense built-up areas and that the low-risk areas are places dominated by a lot of vegetation. A work on the superposition of risk of elevated nighttime temperatures and daytime heat stress was also done.
The report has now been completed and over time the results will be included in Lund Municipality's operational maps. Municipal employees can gain access as early as today by contacting Adam Wadsten.
- An important part of the result is that we can use our analysis to show where actions need to be taken and how to prioritize them, says Adam Wadsten. Some quick measures could, for example, be to create shade by setting up sails at a pre-school or deciding on the basis of our risk analysis which of the preschools is best to have open in the summer. We see the heat mapping as a basis that can justify why measures are needed. We will also move forward with analyses of the warmest areas in relation to more risk groups.
In the work of Lund Municipality there are also a number of examples of measures that can create more coolness in vulnerable places. (see image)
More facts
* Radiation temperature describes the sum of the shortwave and long-wave radiation from the environment to which a human is exposed. The difference in perceived temperature can be more than 30 degrees on a hot summer day, despite the fact that the measured air temperature is similar. Unlike air temperature, radiation temperature also exhibits large local variations and is directly linked to building geometry and vegetation structure, as these affect the amount of solar radiation reaching the ground and facades. Depending on how cities are built, there can be big differences in how different places are experienced.
* The project with heat mapping and risk analysis provides important pieces of the puzzle in the work with the priority areas of LundaEko. In this case, objective 3.6 of the Lund Programme for Ecologically Sustainable Development 2021—2030 —” Preventive climate adaptation - The physical environment in Lund Municipality shall be designed to reduce the vulnerability to risks linked to ongoing climate change between 2021 and 2030.” and objective 3.7 “Preparedness for extreme weather events — The ability of the municipal group to manage the effects of extreme weather events linked to heat, cold and precipitation shall increase between 2021 and 2030.”