A Comparison of the Air Temperature
at Cardiff, Wales and Offwell, Honiton, Devon, U.K.
Sarah (Aged 13)
The main aim of
the experiment was to record and compare the temperature at two locations, namely Cardiff
and Offwell, and to explain any observed differences.
Equipment and Procedures
At Offwell, an electronic sensor connected to a
computer, was used to measure the temperature; this was accurate to 0.1°C. The
thermometer used at Cardiff was a scientific spirit thermometer, which could be read
Both thermometers were placed in identical white plastic tubes for protection from
solar heating. Plastic was found to be the most practical material; although wood or
pottery would both make suitable housing materials, they would be too heavy to send
through the post to Offwell. The tubes were open at one end and had inward facing slots to
keep a current of air flowing around the instrument.
locations the thermometer, in their tubes, were suspended on the south side of a wooden
pole. Both of these poles were situated in a position where they would be in shade in the
early morning and late afternoon, but open for most of the day. This was the most similar
positioning possible between the two locations.
readings were taken every two hours, from 07:00hrs to 19:00hrs for a three-day period. At
Cardiff the thermometer was accessed as follows: at the top of the tube a hole was cut to
the same width as the thermometer, then a rubber washer put around the thermometer. In
this way, the thermometer could be easily accessed by pulling it upwards out of the tube,
but the washer prevented the thermometer from falling through or rainwater getting in and
making the thermometer wet (see Figures 1 & 2).
Figure 1. Photograph
of the housing showing the washer
Figure 2 Taking a reading.
at Offwell was automatically downloaded onto the Internet and accessed by going to the
remote data logging page on the Offwell website (www.offwell.info).
The temperature was displayed in its own window along with the time (see Figure 3). Every minute the latest temperature was updated.
To access this, the refresh button on the browser bar had to be clicked and
the new temperature was displayed. This was repeated successively for three times, and
when three temperatures had been obtained, the highest and lowest readings were discarded
leaving the correct current temperature.
Figure 3. The temperature display on the Internet.
Cardiff, at each reading the general weather was observed and recorded (sun, cloud cover,
wind, rain etc.) As Offwells weather could not be directly recorded, observations
were made from satellite pictures downloaded from the Internet (www.nottingham.ac.uk/meteosat/D2.JPG).
The experiment was run on BST, the satellite images were GMT. Adobe Photodeluxe was used
to enhance the images. On 16-10-02 images
from the www.nottingham.ac.uk/meteosat/D2.JPG
web site were unavailable. Therefore, weather information for Offwell was obtained from
the Met Office UK Observations (http://www.meto.gov.uk/education/archive/uk.html), using
the information for Dunkeswell recording station, which appears to be about 5 miles from