Abstract
Effectively understanding urban climate patterns and heat distribution is essential for developing climate adaptation strategies and mitigating urban risks related to heat stress. The characterization of Urban Heat Islands (UHI) presents significant challenges in mountainous regions, where complex terrain creates unique microclimate conditions that standard approaches often fail to capture adequately. Our research introduces an integrated methodology to examine the UHI phenomenon in Bolzano, an Alpine city situated in northeastern Italy that experiences particularly intense summer heat episodes. Bolzano's distinctive topography—surrounded by steep mountain slopes within a convergence of three valleys—creates a complex thermal environment where mountain-valley circulations significantly influence temperature distribution patterns.
During summer, this topographic configuration can trap heat within the urban core, while winter conditions facilitate persistent cold air drainage and pooling that fundamentally alter the UHI dynamics.
The methodological framework combines innovative mobile monitoring with traditional fixed measurements and numerical modeling. The mobile monitoring system will consist of 25 meteorological sensors MeteoTracker devices) deployed on public transportation vehicles traversing urban-rural areas, collecting continuous temperature, humidity, and pressure data. This mobile system is planned to be deployed after a successful preliminary trial on one bus throughout the entire month of April. This dynamic network is supplemented by fixed weather stations of the official provincial network and quality-filtered observations collected by NetAtmo citizen weather stations. For comprehensive spatial coverage, we also used the outputs from two models: the UrbClim urban climate model at 100-m resolution providing historical simulations (2003-
2022) and future projections (mid-term and long-term) for a range of indicators, and the Weather Research and Forecasting (WRF) model at 1-km resolution, serving as the state-of-reference model for the region over the very recent past (2020-2024). Together, these models provide complementary insights into the spatiotemporal dynamics of temperature patterns across Bolzano's urban landscape and surrounding terrain. The non-hydrostatic WRF model can resolve the thermally driven flows that characterize Bolzano's valley system, capturing the complex circulation patterns that influence heat transport and redistribution. While UrbClim, operating in a simple hydrostatic mode, offers computational efficiency for extended climate simulations, WRF's capabilities allow for a detailed representation of the mountain-valley wind systems that play a crucial role in modulating the UHI effect in this complex topography.
The integration of mobile measurements, fixed observations, and complementary model simulations, allows for an accurate characterization of Bolzano's UHI at multiple spatial and temporal scales. The high spatiotemporal resolution of data provides unprecedented insights into UHI patterns across different weather conditions in this complex Alpine valley environment. By integrating observational networks with detailed physical process representation from WRF and the extended temporal coverage of UrbClim historical simulations, we can effectively document and analyze the unique urban climate dynamics of Bolzano across various periods and spatial scales. Future UrbClim projections help to assess the evolution of current UHI conditions over the next decades, offering a robust foundation for climate adaptation planning in mountainous urban settings.
This research is supported through the RETURN Extended Partnership under the European Union Next-Generation EU program (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005).