RESULTS OF THE METLINK 2000 SURVEY

The maximum and minimum temperatures were recorded at ten sites during a 21 day period. Readings were taken at 8 a.m. and 8 p.m. to get a daily minimum and maximum value, as well as to show the diurnal range. Four of the sites were in urban areas (Wells, Shepton Mallet and Glastonbury), whilst the other five (Bishop Sutton, Pilton, Yarley, Dulcote and Dinder) were in rural areas. A faulty thermometer meant that the values for Theale have been ignored.
Click here to see a map of these data collection points.
Tables 1 and 2 below show the results of the survey, and a comparison between each site and the average temperatures in Wells, showing on how many days during the 21 day period they were either warmer, or cooler than the Wells average. 


 TABLE 1 - COMPARISON OF DAILY MAXIMUM TEMPERATURES BETWEEN EACH SITE AND WELLS 

Site		Days when Warmer 	Days when Cooler
		than Wells		than Wells

Shepton Mallet       13                     8
Glastonbury          14                     7
Bishop Sutton        21                     0
Pilton	              9                     12
Yarley	              6                     15
Dulcote              5                     16
Dinder	              10                    11

 TABLE 2 - COMPARISON OF DAILY MINIMUM TEMPERATURES BETWEEN EACH SITE AND WELLS 

Site		Nights when Warmer 	Nights when Cooler
		than Wells		than Wells

Shepton Mallet        4                    15
Glastonbury           9                    10
Bishop Sutton         6                    15
Pilton	               5                    16
Yarley	               8                    12
Dulcote               7                    13
Dinder	               6                    14
The daily maxima in Table 1 show that Wells was indeed warmer than all of the 5 rural locations, although the two other urban sites (Shepton Mallet and Glastonbury) were warmer than Wells. Perhaps the build-up during the day of the heat island in Wells was affected by the turbulence generated by the Cathedral. The swirling of winds would have mixed the air over the city, perhaps causing warmer urban air to mix with cooler rural air?

wellscath

Yet despite this possible interference to the build up of the heat island, once established, Wells remained warmer for longer. Indeed, the daily minima in Table 2 show that Wells was generally warmer at night than all of the other locations - both urban and rural. Clearly, the city`s historic buildings were retaining their heat and causing evening temperatures to remain higher than those in the surrounding area.

It should not be forgotten that this survey only covered a 21 day period, and it is hoped that further work can be undertaken, building on the results of this preliminary analysis. It would be quite interesting as well to see whether these thermal differences produced other significant differences in other meteorological phenomena such as rainfall and wind speeds.

Click here to find out more about urban microclimates.
Written by Dr.A.K.Hignell - Head of Geography at Wells Cathedral School