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Blog: southern ocean climate models - 13 March

Twice a day at 1pm and 8.30 pm Sean Hartery, NIWA, and Peter Kuma, University of Canterbury, head for the Fantail at the very back of the ship to release their weather balloons.

They have two types of balloons: the larger balloon with a radiosonde attachment, which we have mentioned in an earlier blog, can reach 20 km high, and a smaller balloon called a windsonde that can usually get to about 6 km up. The sondes take measurements of air temperature, pressure, and relative humidity in the atmosphere.

Sean Hartery, NIWA, and Peter Kuma, University of Canterbury, get dressed up in their winter gear to head out from the bridge. The yellow suitcase contains a portable helium inflation kit for the balloons.
Sadie Mills, NIWA

Sean Hartery shows us the lightweight custom-made instrument that attaches to the windsonde.
Sadie Mills, NIWA

 

The lightweight brains of the wind sonde.
Sadie Mills, NIWA

Sean Hartery, NIWA and Pippa Low, University of Auckland up on the fantail filling up the windsonde balloon with helium in the snow.
Peter Kuma, University of Canterbury

 

A small wind sonde being released from the fantail in windy conditions.
Sadie Mills, NIWA

Sean Hartey and John McGregor tracking the progress of the wind sonde after deployment.
Sadie Mills, NIWA

 

Along with the radiosondes that are being released daily, Peter Kuma, University of Canterbury, has installed several instruments around the bridge of the R/V Tangaroa to take recordings from the atmosphere in the Ross Sea that will help him to answer questions about cloud formation and their simulation in climate models in the Southern Ocean. Peter explains what some of these bits of equipment do and how they will help his PhD research:

Snow falling on Peter Kuma’s optical particle counter. The small grey case is an optical particle counter, it measures particles between 0.5 and 20 microns using the scattering of laser radiation. These are particles in the air, which might be dust, seasalt, or particles from plankton, on which cloud droplets can condense (form). So, helping answer the question of whether the presence of the particles in the air samples correlate with the clouds in the air that we are observing. Peter will use these observations to validate a NZ climate model for the Deep South Science Challenge.
Peter Kuma, University of Canterbury

This frozen radar dish is a Micro rain radar. It measures precipitation (rain or snow) using microwave pulses through the atmosphere up to 6km high. Peter will use these data gathered on this voyage to validate the NZ climate model for high latitudes.
Sadie Mills, NIWA

 

Way up on the gantry high above the bridge of the Tangaroa a Ceilometer, which is a type of Lidar or laser radar, sends pulses of infrared radiation into the atmosphere and this bounces back off cloud droplets and ice crystals in the clouds. If clouds are thick then we can only see the cloud base, if they are thin then we can see right through them. This graph is an output from the Ceilometer and shows that the cloud base is at about 1km in this case. The bottom axis of the graph shows time, the side axis shows altitude.

 

Peter Kuma, University of Canterbury

AB Bruce McIntyre and Leading Hand Shane Harvey assist Peter Kuma, University of Canterbury, while he prepares the large helium balloon for his radiosonde.
David Bowden, NIWA

This plot is a skew T-ln P diagram that is produced from every radiosonde balloon deployment. It tells us the thermodynamic profile of the atmosphere. The red line is temperature, the blue line is dewpoint temperature, which is the temperature at which water vapour starts to condense. The point where the two lines get close together is where the cloud base sits, at about 1 km high. Wind direction is shown on the right-hand side, indicating that the wind was northerly near the ground and westerly higher up. In this particular deployment we lost the signal at 7 km high, but usually the radiosondes can reach about 15-20 km.
Peter Kuma, University of Canterbury

Research subject: Climate