Future climate projection of heat indices for Austrian major cities:
Strengthening urban resilience and meeting user needs

1 About e-shape

E-shape is strengthening the benefits for Europe of GEO, Group on Earth Observation, establishing ‘EuroGEO’.
EuroGEO, as Europe’s contribution to the Global Earth Observation System of Systems, aims at bringing together Earth Observation resources in Europe. It allows Europe to position itself as global force in Earth observation through the Copernicus satellite programme, making use of existing European capacities and improving user uptake of the data from GEO assets.

2 Urban Heat in Changing Climate

The local surface energy balance is altered in cities due to (i) high fraction of sealing and (high) building density as well as (ii) comparably low fraction of vegetation land cover. As a result, urban areas have higher ambient temperatures than rural ones, also known as the Urban Heat Island (UHI) effect. Due to the rising urbanization and growing fraction of sealed surfaces on total land use, temperature is increasing in urban areas. Hence, more and more people suffer during extreme heat waves as, e.g., in the summers of 2003 or 2015. In order to counteract the negative effects of heat waves, which are expected to intensify even further in the future (IPCC 2013), and develop urban planning strategies for the mitigation of the UHI, detailed information on thermal conditions within a city is required, including possible development of heat extremes in the future.

3 About the Pilot 7.2

The European Commission implemented several climate services, such as the Copernicus Climate Change Service (C3S) providing climate indicators based on Earth Observation (EO) information and modelling data in order to support different types of end users and decision-makers tackling the problems of climate change. In order to improve the user uptake of the EO data the H2020 project e-shape (EuroGEO Showcases: Applications Powered by Europe) aims to gather these EO resources in Europe and enhance the capabilities of existing European services in addressing different societal challenges. Furthermore, e-shape supports the coordinated exploitation of EO data and services through 27 cloud-based pilot applications in seven thematic areas, as well as the generation of information for these applications together with the users.

As part of e-shape, the showcase “Urban resilience to extreme weather” consists of three pilots with the goal to strengthen resilience and adaptive capacity to extreme weather in summer season on various time-scales (e.g. seasonal forecast to climate projections). The pilot Climate projection products for Austrian cities, carried out by Austrian National Meteorological and Geophysical service (ZAMG), demonstrates the development of climate services for urban regions by creating climate projections for various Austrian cities. This is done by providing high spatial resolution climate information based on the EO data and modelling, focussing on heat indices. Data are made freely available on a national climate data platform (Climate Change Centre Austria (CCCA) data) to support urban planning, risk management and environmental protection. Thereby, the pilot follows the standardization of the method for urban climate modelling and its output to ensure a comparable modelling basis for other European cities.

4 Urban climate model simulations

Within the cooperation with Germany’s National Meteorological Service (DWD), the ZAMG carried out urban climate model simulations with the MUKLIMO_3 model, which allows utilization of various satellite products of Copernicus services (e.g. Urban Atlas, tree cover density etc.) as input data to describe land surface distribution and properties. With the simulation of radiation, soil and atmospheric temperature, relative humidity, and wind flow in urban areas on a 3D grid (100 m spatial resolution, vertical resolution 10-100 m), the model provides the basis for evaluation of the (surface) temperature distribution within urban areas. In combination with meteorological measurements and regional climate model scenarios (representative for the background climate by applying the cuboid method), the model can be used to derive several climate indices related to heat conditions such as the annual average number of summer days (days with maximum air temperature ≥ 25 °C). The regional climate model simulations from the EURO-CORDEX project provide information on meteorological variables until 2100 under various climate change scenarios, e.g. RCP4.5 and RCP8.5 (IPCC, 2013). An ensemble of model output for different RCP scenarios is used to project future heat conditions in urban areas. In the pilot, eight different combinations of bias corrected regional/global climate model output were used to calculate climate indices for each year between 2011 and 2100.