Mapping and monitoring of km scale urban climate impacts due to changes in land cover and atmospheric conditions

Land cover changes are one of the most important anthropogenic drivers of global climate change. On the urban scale, land cover changes influence the radiation budget and the energy balance and can contribute to the development or intensification of the urban heat island (UHI) phenomena. The UHI is a typical feature of the urban climate and is determined by the cities structure and use of building and sealing materials. The UHI intensity is quantified by the difference in air temperature between the warmer city and its surrounding, cooler countryside and reaches its maximum during night-time under cloudless and calm weather conditions. In large cities UHI intensity can reach magnitudes of about 10 Kelvin. The ongoing trend of urbanisation meaning land cover changes from an unsealed, vegetated area to sealed urban area are exacerbating the UHI intensity. Especially in summer months, the additional heat load in the city is affecting the wellbeing of the population. Another approach to monitor and analyse the phenomena of the warmer city is to analyse land surface temperature (LST) data delivered by earth observation. In such case, the term surface urban heat island (SUHI) is used.

Within the proposed action hourly gridded UHI intensity and air temperature data with a spatial resolution of 1 km² for Germany will be calculated for a multi-year period and compared to data of the Deutscher Wetterdienst (DWD) urban climate station network. Urban climate impacts caused by changes in land cover and trends in atmospheric weather conditions will be statistically analysed and mapped for entire Germany. The Copernicus Land Monitoring Pan-European Service CORINE Land Cover (CLC) provides the time series of change layers, which highlight changes in European land cover during the time period from 1990 till 2018. The results of the proposed action (maps of UHI intensity and climate indices data) will represent an innovative and very valuable data source for nationwide urban climate monitoring and the applied methodology can be transferred to other EU member states. The final product will be available on the DWD website in the form of visualized UHI and air temperature datasets. Additionally, maps of climate indices and statistical analysis will be developed and provided online.

SUHI analyses will be performed for two selected cities (Dresden and Wrocław). Currently there is a number of satellites providing LST data (e.g. Sentinel-3A, Sentinel-3B, Meteosat), but there is no service which uses this data for operational SUHI analyses. Using available LST products, SUHI will be analysed on different time scales (daily, monthly, seasonally and yearly). High resolution, yearly updated land cover data based on Copernicus will be combined with Sentinel-3 LST data to enable tracking in time the differences between LST in different parts of the cities (with different ratio between green and imperviousness areas) and their surroundings. Based on the results of this study, a methodology for SUHI monitoring will be developed, as well as a new service. The city authorities of Wroclaw and Dresden confirmed their overall interest as pilot cities. The representatives of the two pilot cities will be engaged via regular face-to-face or web-meetings and will test and evaluate the SUHI and UHI product design.

The new applications are mainly targeted for the user group municipalities, including the city administration, politicians, municipal companies, stakeholders and the public. The data and maps should help municipalities and local stakeholders to better monitor the development of their overall urban thermal climate, to quantify adaptation deficits at the regional scale and to take action and adapt to climate change impacts were necessary.

During the co-creation process, which comprises the data analysis and result phase, as well as the design phase of the products, the feedback of end-users from different municipalities is collected and included. This will be done via workshops and questionnaires. The engagement of more users is crucial for the product development since the knowledge base and needs of the municipalities are very divers. To identify the needs and to develop user-friendly products from data provisions to aggregated information via maps and statistics is the main task of this project. The user feedback goes directly into the product development and design.