Framing Seasonal Changes at the Urban Microscale using FMP2.0 data

Seasons and their transitions play a critical role in shaping ecosystems and human activities, yet their traditional classifications—meteorological and astronomical—fail to capture the complexities of biosphere-atmosphere interactions. Conventional definitions often overlook the interplay between climate variables, biosphere processes (including human activities), and the actual anticipation of seasons, particularly in the context of global climate change, which has disrupted traditional seasonal patterns. As the climate becomes increasingly variable, the need to redefine how we observe and interpret seasonal change becomes more urgent—not only for ecological and scientific understanding but also for societal adaptation. Urban environments are increasingly recognized as dynamic interfaces where climatic variability, human activity, and biosphere responses converge—often in ways that diverge from traditional seasonal classifications. This study explores seasonal transitions through continuous micrometeorological measurements in three contrasting European cities: Novi Sad (Serbia), Thessaloniki (Greece), and Cardiff (UK), using data from the FAIRNESS micrometeorological platform (FMP2.0). Utilizing the normalized daily temperature range—a biologically grounded seasonality index previously validated in agricultural zones (Lalić et al., 2022; Lalić and Firanj Sremac, 2025)—we identify and characterize the onset, duration, and transition phases of seasons within urban microclimates. Our results reveal distinct spatial and temporal patterns, with clear seasonal offsets and variable transition durations across the cities, reflecting both geographic and anthropogenic influences. These findings not only challenge conventional meteorological and astronomical definitions but also highlight the urban-specific reshaping of seasonal cycles under climate change. The methodology provides scalable and perceptually aligned metrics for urban seasonality, with implications for urban planning, public health, market behaviour, and policy design. As climate variability intensifies, rethinking seasonality through the lens of city-based micrometeorological data becomes crucial for adaptive decision-making across diverse sectors.

Acknowledgements: This research is supported by the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (Grants No. ‪451-03-137/2025-03/ 200125 & 451-03-136/2025-03/ 200125) and COST Action CA20108 FAIR Network of micrometeorological measurements (FAIRNESS).