27 March 2004

Saturday, 27 March 2004

Looking up

Another calm day in the Southern Ocean, but rumour has it, that we will be facing 50-knot southerly winds by tonight, so everyone is frantically getting in some good work before the going becomes too difficult.

I am part of the atmospheric group, working in a cramped container laboratory on the forecastle deck. This laboratory is crammed full of gear and we are high above the poor souls scrambling for seawater from the CTD. This doesn't mean our lab is entirely free from seawater, since our position is quite exposed and we did receive a drenching from a huge wave that broke over the container. This had us mopping up and drying out a few instruments – while duct-tape has many amazing properties, sealing windows against waves, is obviously not one of them!

Our group are looking for the changes in the atmosphere as a result of the hoped for plankton bloom. The plankton produce many gases that are released into the atmosphere (this process is being studied by the physics group), one gas, dimethylsulfide, is being measured in seawater and our aim is then to directly measure the amount of this gas leaving the ocean, using intakes on the bow mast.

Typically the levels of dimethylsulfide (and hence sulfur dioxide and particles) are at their highest when the plankton bloom is dying and so, for us atmospheric scientists most of the excitement of this cruise will come towards the end, rather than at the beginning. Once in the air dimethylsulfide is converted to another gas, sulfur dioxide - this is what I am trying to measure.

Sulfur dioxide is converted to tiny particles (aerosols) and we have two instruments determining the concentration of these particles in the air. Another sampler on the bow mast collects these tiny particles on a series of filters to allow us to determine their chemistry when we return to shore.

Aerosols are important for the formation of clouds, allowing water vapour to condense and thus form clouds. Clouds reflect some sunlight back to space, thereby cooling the Earth’s surface.

One other activity that occurs from our container is the launching of radiosondes – these are small packages, able to monitor temperature, humidity, pressure and wind speed and direction. The package is attached to a large helium-filled meteorological balloon and then released. The balloon continues to rise, transmitting data back to a receiver in the container. These sondes give us information on the structure of the atmosphere and can fly up to heights of tens of kilometers.

The atmospheric group

The group includes:

  • Jill Cainey (Australian Bureau of Meteorology)
  • Mike Harvey (NIWA)
  • Murray Smith (NIWA)
  • Dawn DeVries (University of Colorado)
  • Peter Minnett (University of Miami)

Jill Cainey, Australian Bureau of Meteorology

Atmospheric scientists at work in our crowded container lab.

Release of the radiosonde from the ship's deck.

Research subject: Oceans