CMMP - Water temperature

Chesil Multi-Media Project
Fleet water temperatures

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Equipment

Instrumentation

The water temperature in the lower Fleet is measured on a regular basis using a Meteorological Office sea temperature bucket. This measurement is made on each visit to the Black Hut and is made in the same place and, as near as possible, the same time of day. At the same time the sea temperature measured by the Weymouth Bay Waverider buoy operated by the Channel Coast Observatory is obtained and the two temperatures plotted as shown below. The horizontal scale is four months per box.

The Fleet measurement is made on the edge of the main channel at a depth of 1 metre. The measurement is made at approximately 14:30 (local) each time that the CMMP equipment is visited. This is usually at least once a week.

The Weymouth Bay buoy data only became available in late 2006 and this is shown in purple in the graph above. As a general rule, the water in the Fleet is warmer than Weymouth Bay in the summer, and colder in the winter. This becomes more pronounced further up the Fleet, but even in the lower Fleet there is a significant difference.

Generally the sea is at its coldest in mid-February and at its warmest in mid-August. We have now passed the coldest temperature but the minimum is being prolonged by spells of cold weather. The temperature has now started to rise as the days lengthen and the sun gets higher in the sky. Note the considerable variation in the Fleet temperature, dependant on whether the tide is ebbing or flowing. As we go into Spring the water in the upper Fleet changes from being colder than the water in Portland Harbour to being generally warmer. This means the water temperature on the ebb tide will generally be warmer than the temperature measured during the flood tide.

Last updated 02/04/2008