A Comparison of the Air Temperature
     at Cardiff, Wales and Offwell, Honiton, Devon, U.K.

                        

By Sarah (Aged 13)

 

1. Introduction

 

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.

                                                                             

2. The 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
to 0.25°C.   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.

At both 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.

Temperature 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).

 

The temperature 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.

 

In Cardiff, at each reading the general weather was observed and recorded (sun, cloud cover, wind, rain etc.) As Offwell’s 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 Offwell.