London’s Urban Heat Island - During A Warm Summer

For an urban heat island map during an average summer see this dataset.

A heatwave refers to a prolonged period of unusually hot weather. While there is no standard definition of a heatwave in England, the Met Office uses the World Meteorological Organization definition of a heatwave, which is "when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5°C, the normal period being 1961-1990". They are common in the northern and southern hemisphere during summer have historically been associated with health problems and an increase in mortality.

The urban heat island (UHI) is the phenomenon where temperatures are relatively higher in cities compared to surrounding rural areas due to, for example, the urban surfaces and anthropogenic heat sources.

This urban heat island map was produced using LondUM, a specific set-up of the Met Office Unified Model version 6.1 for London. It uses the Met Office Reading Surface Exchange Scheme (MORUSES), as well as urban morphology data derived from Virtual London. The model was run from May until September 2006 and December 2006. This map shows average surface temperatures over the summer period of 2006 at a 1km by 1km resolution. To find out more about LondUM, see the University of Reading’s website.

The hourly outputs from LondUM have been aggregated and mapped by Jonathon Taylor, UCL Institute for Environmental Design and Engineering. Variables include:

• WSAVGMAX= the average of the maximum daily temperatures across the summer period (May 26th-August 31st)
• WSAVG=the average temperature across the summer period
• WSAVGMIN = the average minimum daily temperature across the summer period
• HWAVGMAX= the average of the maximum daily temperatures across the 2006 heatwave (July 16th-19th)
• HWAVG=the average temperature across the across the 2006 heatwave
• HWAVGMIN = the average minimum daily temperature across 2006 heatwave period

The maps are also available as one combined PDF.

The gif below maps the temperatures across London during the four-day period of 16-19th July, which was considered a heatwave.

If you make use of the LondUM data, please use the following citation to acknowledge the data and reference the publication below for model description:

LondUM (2011). Model data generated by Sylvia I. Bohnenstengel (*), Department of Meteorology, University of Reading and data retrieved from http://www.met.reading.ac.uk/~sws07sib/home/LondUM.html.

(*) Now at Metoffice@Reading, Email: sylvia.bohnenstengel@metoffice.gov.uk

Bohnenstengel SI, Evans S, Clark P and Belcher SeE (2011) Simulations of the London Urban Heat island. Quarterly journal of the Royal Meteorological Society, 137(659). pp. 1625-1640. ISSN 1477-870X doi 10.1002/qj.855. LondUM data (2013).