Ballooning

So as promised, a science post! As well as spotting wildlife and taking photos, the meteorology team on Oden are busy making measurements. One of the more hands-on of these are radiosondes, which we are responsible for launching four times a day, every six hours, throughout the 3 months of the cruise.

Radiosondes are a small instrument package, consisting of temperature, humidity and pressure sensors, plus a GPS antenna and an aerial for communicating the measurements back to the base station (Photo 1). The instrument package is attached to a balloon filled with helium, which rises through the atmosphere. As the balloon rises, the GPS enables wind speed to be estimated from the difference in position if the base station and the sonde.

A radiosonde

A radiosonde

The instruments are used to get a profile up through the atmosphere, that is, a measurement of the variation in temperature, humidity and wind speed with height. The radiosonde is the workhorse instrument of meteorology and atmospheric physics; by directly measuring the profiles we can diagnose the physical state of the atmosphere at that location, obtain some of the key information required for weather forecasting and climate modelling, and calibrate remote sensors (such as those based on satellites, or the radiometers we have installed on Oden).

Filling the balloon

Filling the balloon

Launching a radiosonde involves setting the instrument up, filling the balloon, attaching the sonde to the balloon (Photo 2), then releasing it. Once the sounding has finished, usually because the balloon bursts (at a height of around 23 km for the balloons we use on Oden), the data is archived and then sent to meteorological agencies to be incorporated into weather forecasts. In normal conditions, preparing and launching a radiosonde is straightforward (Photo 3). On a moving ship with high winds, turbulent eddies from the ship’s superstructure, and freezing rain covering surfaces, including the balloon, with ice, things can be a little trickier (Photo 4).

Barbara launching a balloon during a pleasant Arctic morning. (Photo by Dan Wolfe)

Launching the balloon

 Dan trying to stop Rez being launched with the balloon on a very windy day

Dan trying to stop Rez being launched with the balloon on a very windy day

For this cruise on Oden, we are particularly interested in conditions near the edge of sea ice areas, so we have been launching extra sondes in these locations. As there are very few radiosonde launches occurring in the region we are in, our radiosondes have a larger than usual impact on local forecasts, which in turn help the other scientists and crew on Oden to plan their work.

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