EGU25-15275, updated on 01 Jul 2025
https://doi.org/10.5194/egusphere-egu25-15275
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Urban effects on atmospheric boundary-layer clouds, mixed-layer height and fog detected by a dense network of ceilometers in Berlin, Germany
Daniel Fenner1,2, Andreas Christen2, Sue Grimmond3, Simone Kotthaus4, Fred Meier1, and Matthias Zeeman2
Daniel Fenner et al.
  • 1Chair of Climatology, Technische Universität Berlin, Berlin, Germany (d.fenner@tu-berlin.de)
  • 2Chair of Environmental Meteorology, University of Freiburg, Freiburg, Germany
  • 3Department of Meteorology, University of Reading, Reading, UK
  • 4LMD-IPSL, École Polytechnique, Paris, France

Gaining a deeper understanding of dynamic interactions between cities and the atmospheric boundary layer (ABL) and ABL processes in general is crucial for, e.g., the development and application of next-generation numerical weather prediction and climate modelling. In this context, detailed ABL observations provide essential information to identify potential spatial heterogeneity in urban and rural environments with respect to surface-atmosphere exchanges and resulting ABL characteristics such as ABL clouds.

As part of the year-long urbisphere-Berlin measurement campaign in Berlin, Germany (October 2021-September 2022), a wide range of ABL observations were carried out to study impacts of the city on the ABL. Central to the deployed systematic network were 25 sites with ground-based Automatic Lidar and Ceilometers (ALC) to measure aerosol backscatter for investigation of intra-urban, urban-rural, and upwind-city-downwind effects of ABL clouds and detection of the mixed layer.

Here, we present a systematic investigation of year-round effects of the city on ABL cloud-base height and cloud-cover fraction, mixed-layer height, and near-surface fog conditions, exploiting the dense ALC network. The comprehensive data set allows studies along diurnal and annual cycles in high temporal resolution, as well as obtaining robust statistical results for groups of sites, considering spatial heterogeneity due to local effects around the sites. Our analyses show city effects on ABL clouds along the diurnal cycle including upwind-city-downwind effects, yet also depending on cloud type and season. Mixed-layer height undergoes a distinctive annual cycle, being systematically higher above the city and with intra-urban differentiation. Over the year, the occurrence of ground-based fog is on average 1,5 times more frequently found at rural sites compared to city sites, most prominent differences are found during autumn and winter. These results are the first that are based on the complete year-long urbisphere-Berlin ALC data and highlight potentials and benefits of such high-resolution observational data sets from ground-based remote sensing for future investigations.

How to cite: Fenner, D., Christen, A., Grimmond, S., Kotthaus, S., Meier, F., and Zeeman, M.: Urban effects on atmospheric boundary-layer clouds, mixed-layer height and fog detected by a dense network of ceilometers in Berlin, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15275, https://doi.org/10.5194/egusphere-egu25-15275, 2025.