Urban Heat Island Dynamics in Berlin and Dependency on Lamb Weather Types

Urban heat islands (UHIs) are widely recognized as one of the clearest indicators of anthropogenic modification of the local climate system, resulting from the transformation of natural land surfaces into dense built environments characterized by altered thermal, radiative, and hydrological properties. The replacement of vegetated surfaces with impervious materials such as asphalt and concrete significantly modifies the surface energy balance, promoting heat storage during daytime and delayed release during nighttime, thereby enhancing urban–rural thermal contrasts. This study investigates the urban heat island (UHI) over the Berlin metropolitan region using a long-term high-resolution gridded dataset of daily minimum temperature from the EMO-1 (European Meteorological Observations gridded meteorological dataset with a spatial resolution of 1 arcmin × 1 arcmin) dataset, combined with Lamb weather types (LWTs) representing large-scale atmospheric circulation patterns. The analysis covers the period 1990–2023, enabling robust detection of long-term trends and variability. UHI intensity is quantified relative to a dynamic rural baseline defined by the 10th percentile temperature, allowing improved robustness compared to fixed rural references and reducing biases associated with spatial heterogeneity. Results demonstrate a persistent UHI centered over the urban core, with pronounced seasonal variability and statistically significant warming trends ranging from 0.004 to 0.018 °C yr−1 across circulation regimes. Anticyclonic and Unclassified conditions dominate both the frequency and magnitude of UHI trends, confirming the dominant role of synoptic forcing controlling urban thermal dynamics. These findings underscore the necessity of integrating large-scale atmospheric circulation into UHI assessments and urban climate modeling.