Abstract/Summary

For next-generation weather and climate numerical models to resolve cities, both higher spatial resolution and sub-grid parameterizations of urban canopy-atmosphere processes are required. Key is to better understand intra-urban variability and urban-rural differences in atmospheric boundary layer (ABL) dynamics. This includes upwind-downwind effects due to cities’ influences on the atmosphere beyond their boundaries. To address these aspects a network of >25 ground-based remote-sensing sites was designed for the Berlin region (Germany), considering city form, function, and typical weather conditions. This allows investigation of how different urban densities and human activities impact ABL dynamics. As part of the interdisciplinary European Research Council Grant urbisphere, the network was operated from Autumn 2021 to Autumn 2022. Here we provide an overview of the scientific aims, campaign setup, and results from two days, highlighting multi-scale urban impacts on the atmosphere in combination with high-resolution numerical modeling at 100 m grid-spacing. During a spring day, the analyzes show systematic upwind-city-downwind effects in ABL heights, largely driven by urban-rural differences in surface heat fluxes. During a heatwave day, ABL height is remarkably deep, yet spatial differences in ABL heights are less pronounced due to overall dry soil conditions, resulting in similar observed surface heat fluxes. Our modeling results provide further insights into ABL characteristics not resolved by the observation network, highlighting synergies between both approaches. Our data and findings will support modeling to help deliver services to a wider community from citizens to those managing health, energy, transport, land-use and other city infrastructure and operations.