Extreme heat events are natural hazards affecting many regions of the world. This study uses an example of the six largest cities in Austria to demonstrate the potential of urban climate model simulations applied in prediction mode providing detailed information on thermal conditions. For this purpose, the urban climate model MUKLIMO_3 of the German Meteorological Service (DWD) coupled with the hydrostatic numerical weather prediction model, ALARO, is used to simulate the development of the urban heat island (UHI) in Austrian cities for the summer period of 2019 with a horizontal resolution of 100 m. In addition to the evaluation of UHI predicting skills, other relevant variables, such as humidity and wind characteristics on hourly basis, are also analysed in this paper. Model evaluation confirmed that the MUKLIMO_3 microscale model had the capacity to simulate the main thermal spatiotemporal patterns in urban areas; however, a strong dependence on the input data from the mesoscale model was found. Our results showed large benefit in prediction of maximum air temperatures in urban areas, while the relative humidity predictions of MUKLIMO_3 appear to be much less plausible and show large variety of model prediction skills. Urban climate model simulations using real atmospheric conditions can facilitate better quantification and understanding of day-to-day intra-urban variations in microclimate as well as provide a basis for evaluation of the microclimate prediction skills of mesoscale numerical models with urban extensions.

Urban environments experience amplified thermal stress due to the climate change, leading to increased health risks during extreme temperature events. Existing numerical weather prediction systems often lack the spatial resolution required to capture this phenomenon. This study assesses the efficacy of a coupled modeling system, the numerical weather prediction AROME model and the land-surface model SURFace EXternalisée in a stand alone mode (SURFEX-SA), in forecasting air temperatures at high resolutions ($2.5$km to $100$m) across four Austrian cities (Vienna, Linz, Klagenfurt and Innsbruck). The system is updated with the, according to the author’s knowledge, most accurate land use and land cover input to evaluate the added value of incorporating detailed urban environmental representations. The analysis focuses on the years 2019, 2023, and 2024, examining both summer and winter seasons. SURFEX-SA demonstrates improved performance in specific scenarios, particularly during nighttime in rural and suburban areas during the warmer season. By comprehensively analyzing this prediction system with operational and citizen weather stations in a deterministic and probabilistic mode across several time periods and various skill scores, the findings of this study will enable readers to determine whether high-resolution forecasts are necessary in specific use cases.

The high-resolution INCA system (Integrated Nowcasting through Comprehensive Analysis) provides gridded analyses and short-term forecasts of meteorological fields at a horizontal resolution of 1 km and at 5 to 60 min temporal resolution. After the nowcasting part, INCA fields are blended into AROME or a statistically optimized combination of NWP models, thus providing a seamless chain of forecasting fields at various scales. As an operational product of the national Austrian weather service (ZAMG), INCA is employed for a number of applications, such as for hydrological runoff modelling, severe weather warnings, in road safety, agriculture and in the renewable energy sector. The product development is embedded into the research activities of the last year period which, amongst others, included the development of new blending methods into the state of the art NWP models, a new approach for precipitation analysis and nowcasting as well as the evaluation of wind, temperature and humidity analyses at 100 m horizontal resolution. For precipitation, a new radar-raingauge merging algorithm has been developed, which is based on station density and radar minimum beam height. Precipitation nowcasting uses optical flow and nested subdomains for breaking down the displacement vectors to the target grid. In the sub-kilometer version, the improvements due to the topography-relevant features (i.e. altitude, slope) in Alpine areas are shown as well as the potential benefits of high resolution nowcasting in urban areas. The methods and related results will be presented along with a comprehensive verification.