Urban green space and peri-urban forest microclimates in the city of Augsburg, Germany: A seasonal and synoptic perspective

Source abstract

Urban green spaces (UGS), including peri-urban forests, are recognised as effective climate adaptation measures. However, research into the microclimate characteristics of different UGS structures under varying diurnal, seasonal and synoptic conditions is scarce. Over two annual cycles, this study collected climate data from five structurally diverse UGS and one vegetated residential district across Augsburg, Germany The UGS covered mixed forests, pine forest, heathland, and an urban park. Results show that diurnal air temperature contrasts exceeded seasonal and synoptic variability across all sites. Mixed forests exhibited the largest daytime cooling capacity and the least diurnal temperature variability. Although the urban park exhibited higher cooling capacity than the pine forest and heathland at noon, its nighttime cooling effect relative to the peri-urban forests was modest. Air temperature differences between the UGS structures increased with warmer weather and vice versa. Large-scale weather conditions either dampened temperature contrasts under cool, windy and overcast situations or amplified them during calm, clear-sky conditions. Mixed-effects modelling indicated that tree density had the strongest overall association with lower air temperatures, particularly at night. In contrast, tree height was linked to moderate daytime cooling but consistent nighttime warming, presumably due to reduced longwave radiative losses. During a heatwave event, mixed forests reduced maximum Modified Physiologically Equivalent Temperature by around 6 °C. These findings inform heat action planning by showing that the UGS cooling efficiency depends on weather conditions and time of day, and that structurally diverse mixed peri-urban forests reduce heat stress most effectively.