FOR countries on the edge of western Europe, one of the difficulties of forecasting the weather is the dearth of information from the vast expanse of ocean to the west. Strategically placed weather ships traditionally provided data of this kind, but weather ships are expensive to operate, and since the beginning of the satellite era there has been a tendency to phase them out. Unfortunately, however, the information from satellites alone is not as accurate as one might wish.
Satellite data cover a very large area, and show in very great detail how temperature, cloud and other elements vary from one region to another. To get the best out of them however, it is still desirable to have a good network of accurate instruments at ground level - "ground truth" as meteorologists like to call it. The information from this network can then be used to interpret the satellite images more effectively.
In the absence of weather ships, ocean buoys are useful for this purpose. They are fitted out with instruments to measure air and sea temperature, pressure, humidity and other elements of interest to the forecaster, and the data is relayed to the satellite based ARGOS navigation system. ARGOS, operated from the American NOAA series of polar orbiting satellites, not only relays the weather information back to land based stations, but also continually monitors the geographical position of the buoys, so that we know from which spot on the globe each weather report has come.
Some of these weathers buoys are anchored at a particular spot in shallow waters, but the majority are "drifting buoys", free to run with the winds and currents like roving reporters on the oceans of the world. The position at which each drifting buoy is initially dropped is chosen carefully, taking account of gaps in the present network and the likely track the buoy will follow as it is driven by prevailing winds and seas.
Many in this part of the world are deployed by "ships of opportunity" - ordinary merchant ships who agree to take the buoy on board at the beginning of a voyage and drop it overboard at some designated spot. In the North - Atlantic, a favourite launching place is somewhere near the tip of Greenland from where the buoy generally moves eastwards, passing close to Iceland before curving south - until perhaps a year or so later it may end its life as flotsam on some unknown and silent, rocky shore.
"There is a tide in the affairs of men", and so it is with meteorologists -
And we must take the current when it serves,
Or lose our ventures.