The British Antarctic Survey (BAS) and the Dewmet S.D. dewpointmeter (July 2001)

The British Antarctic Survey (BAS) has recently used Michell Instruments' Dewmet S.D. dewpointmeter in atmospheric physics studies on expedition in the Arctic. The Dewmet S.D. system uses cooled mirror technology to measure moisture content accurately and reliably. The dewpointmeter's extremely quick response to changing environmental conditions, rugged design to withstand adverse conditions and wide effective measurement range - from -50ºC to +90ºC - make it an ideal tool for climate monitoring in the Arctic.

The BAS, which has headquarters in Cambridge, undertakes a world-class scientific programme in the Antarctic and related regions, including the Arctic, and addresses key global and regional issues through research, surveying and monitoring. The polar regions play a major role in the global climate, but many of the processes that control the climate systems of the Arctic and Antarctic, and couple them to the global climate system, are imperfectly understood. Dewmet S.D. was used on a six-week ship-borne experiment in the Arctic by BAS scientists to help improve their understanding of such processes.

According to Dr John King, Principal Investigator, Antarctic Climate Processes, "We used Dewmet S.D. in a series of atmospheric physics studies for a particular experiment looking at the exchange of heat momentum and water vapour from surface to atmosphere on the fringes of the perennial sea-ice covering. We needed accurate and stable equipment to take measurements of mean relative humidity and Dewmet S.D. enabled us to do so."

Dewmet S.D. was used to take dewpoint measurements typically between -5ºC and +15ºC to a precision of 0.1ºC . The hygrometer was connected to a data-logging system developed by Southampton Oceonography Centre and was used in tandem with other instruments, including a fast-response infrared hygrometer and a sonic anemometer, as well as conventional slow-response anemometers and resistance thermometers, to measure other climatological conditions.

Dewmet S.D. was chosen for the six-week expedition, as the BAS required robust equipment that would work in a marine environment and would function throughout the trip without the need for constant supervision. The BAS also needed the accuracy of humidity measurement offered by cooled mirror equipment. As Dr King adds, "Dewmet S.D. offered us the right balance between price and accuracy and, as Michell Instruments is a local firm, we could talk to them and discuss our requirements in detail. Since what we are doing is out of the ordinary, we like to build up close relationships with suppliers. We feel that this has come to fruition with Michell Instruments, and can see it continuing in the future."

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