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Chasing Clouds in the Southern Ocean - SOCRATES Project

This month, scientists from the US, Australia and from KIT are investigating one of the biggest mysteries in our current climate - namely the clouds over the stormy Southern Ocean. The field campaign, named the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), is an unique campaign in the way that it will provide airborne in-situ observations from an area where measurements have been scarce. The airborne observations are performed with the NSF/NCAR GV HIAPER aircraft that is a long range measurement aircraft with a relatively large payload. Research flights will be performed from Hobart, Tasmania (41°S) towards south to latitudes of about 60°S and beyond.

NSF/NCAR HIAPER taking off for the first science flight

Since KIT is the only participating European research institution, SOCRATES is a once-in-a-lifetime opportunity for me to perform in-situ cloud microphysical measurements at the remote Southern Ocean. Furthermore, it will be the first time that we can test a new method for discriminating small ice particles from droplets in the Southern Ocean mixed-phase clouds using the PHIPS probe. Previous observations of the ice phase in the Southern Ocean have limited to ice particles larger than 100 µm (observations made with the 2D-C probe; Chubb et al., 2013) or have been gathered qualitatively using the Rosemount icing rate detector (SOCEX I & II; Boers et al., 1998). During SOCRATES the PHIPS single particle angular light scattering information will be used to discriminate between droplets and ice down to ~10 µm particle sizes.


The biggest question in the Southern Ocean is the large amount of supercooled water that is observed but not captured by the models. The puzzle is, how come the cloud particles stay in a liquid phase, and why so little ice is observed. I hope that the PHIPS observations will bring clarity to the question of ice particle concentrations and to the processes related to ice formation. The experience gathered from the Arctic mixed-phase clouds last summer will certainly be useful when interpreting the data from the Southern Hemisphere. Independent what the observations will tell, the data that we'll be gathering the next months will be unique in many ways.

NCAR/NSF GV HIAPER taking off towards the Southern Ocean


Boers, R., Jensen, J. B. and Krummel, P. B. (1998). Microphysical and short wave radiative structure of stratocumulus clouds over the Southern Ocean: Summer results and seasonal differences. Q. J. R. Meteorol. Soc., 124, 151–168.

Chubb, T. H., Jensen, J. B., Siems, S. T. and Manton, M. J. (2013). In situ observations of supercooled liquid clouds over the Southern Ocean during the HIAPER Pole to Pole Observation (HIPPO) campaigns, Geophys. Res. Lett., 40, 5280–5285.

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