Published March 24, 2022 | Version v1
Journal article Open

Evidence of horizontal urban heat advection in London using six years of data from a citizen weather station network

  • 1. UCL Institute for Environmental Design and Engineering, The Bartlett Faculty of Environment, University College London, London, United Kingdom
  • 2. Bioengineering Sciences Research Group, Department of Mechanical Engineering, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, United Kingdom
  • 3. Chair of Environmental Meteorology, Institute of Earth and Environmental Sciences, Faculty of Environment and Natural Resources, University of Freiburg, Germany
  • 4. Chair of Climatology, Institute of Ecology, Technische Universität Berlin, Germany
  • 5. Department of Civil Engineering, Tampere University, Tampere, Finland
  • 6. UCL Institute for Environmental Design and Engineering, The Bartlett Faculty of Environment, University College London, London, United Kingdo

Description

Recent advances in citizen weather station (CWS) networks, with data accessible via crowd-sourcing, provide relevant climatic information to urban scientists and decision makers. In particular, CWS can provide long-term measurements of urban heat and valuable information on spatio-temporal heterogeneity related to horizontal heat advection. In this study, we make the first compilation of a quasi-climatologic dataset covering six years (2015–2020) of hourly near-surface air temperature measurements obtained via 1560 suitable CWS in a domain covering south-east England and Greater London. We investigated the spatio-temporal distribution of urban heat and the influences of local environments on climate, captured by CWS through the scope of Local Climate Zones (LCZ)—a land-use land-cover classification specifically designed for urban climate studies. We further calculate, for the first time, the amount of advected heat captured by CWS located in Greater London and the wider south east England region. We find that London is on average warmer by about 1.0 C–1.5 C than the rest of south-east England. Characteristics of the southern coastal climate are also captured in the analysis. We find that on average, urban heat advection (UHA) contributes to 0.22 ± 0.96 C of the total urban heat in Greater London. Certain areas, mostly in the centre of London are deprived of urban heat through advection since heat is transferred more to downwind suburban areas. UHA can positively contribute to urban heat by up to 1.57 C, on average and negatively by down to −1.21 C. Our results also show an important degree of inter- and intra-LCZ variability in UHA, calling for more research in the future. Nevertheless, we already find that UHA can impact green areas and reduce their cooling benefit. Such outcomes show the added value of CWS when considering future urban design.

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Funding

urbisphere – urbisphere - coupling dynamic cities and climate 855005
European Commission