Methodology to separate urban from regional heat advection by use of the Weather Research and Forecasting mesoscale model

Richard Bassett, Xiao Ming Cai*, Lee Chapman, Clare Heaviside, John Thornes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Recent studies have identified the significance of urban heat advection (UHA) as the process whereby heat, originally generated through urban modifications to the Earth's surface, is transported downwind of urban areas. Current techniques to separate UHA from local heat signals do not exclude the additional potential impacts of regional heat advection (RHA). For example, large-scale coastal effects, in addition to latitude and longitude variations, could cause downwind temperature gradients to exist. In this study, the numerical Weather Research and Forecasting (WRF) model coupled with the Building Effect Parameterization (BEP) urban scheme is used to simulate meteorological fields for Birmingham, UK, at a high horizontal resolution (1 km2). The model is run over six case-studies to provide over 1600 h of simulations (called ‘urban-case’), and evaluated using a unique high-resolution dataset from 32 weather stations across Birmingham. The UHA component is decomposed from RHA by conducting a second set of simulations (called ‘rural-case’), where all urban land-use is replaced with vegetation. Simulated directional ‘rural-case’ time-mean temperature fields, that show RHA, are then subtracted from the equivalent ‘urban-case’ time-mean fields. This effectively separates UHA from RHA and shows that a significant portion of heat, previously attributed to UHA in mesoscale modelling, is found to be due to RHA. Using the new methodology, a UHA signal up to 1.9 °C is found largely confined to within, and several kilometres downwind of, the urban areas. These UHA effects highlight the importance of using wind direction segmentation when determining local climate.

Original languageEnglish
Pages (from-to)2016-2024
Number of pages9
JournalQuarterly Journal of the Royal Meteorological Society
Volume143
Issue number705
DOIs
Publication statusPublished - Apr 2017

Bibliographical note

Funding Information:
This research was principally supported by a Natural Environment Research Council CASE (Collaborative Award in Science and Engineering) studentship (grant number NE/K008056/1). The research was also part funded by Birmingham City Council. We thank Birmingham Urban Climate Laboratory for providing AWS data and the British Atmospheric Data Centre for Met Office station data. The computations described herein were performed using the University of Birmingham's BlueBEAR HPC service (http://www.bear.bham.ac.uk).

Publisher Copyright:
© 2017 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society.

Keywords

  • WRF
  • mesoscale modelling
  • regional heat advection
  • temperature
  • urban heat advection
  • urban heat islands

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