Last Days

Today is the last day for me at Princess Elisabeth station. Tomorrow we will fly to the Russian Novo Air Base and on Thursday then to Cape Town. The last days are filled with de-installing the instruments which have to go back to Belgium for calibration or adaption reasons, and to prepare the other instruments for winter operation. All my instruments have been measuring fine so far, so I am right away satisfied. There was a lot of sunny weather, and the ozone spectrophotometer and the sun photometer had done a lot of good measurements. Also the condensation particle counter (measuring the number of particles in the air) turned out to behave smoothly. Most of the time there are low particle concentrations of around 300 to 500 particles per cubic centimetres. If one would measure, e.g., in Brussels, the concentrations were 100 to 1000 times higher. Our instrument is really sensitive – detecting immediately if the station’s bulldozer, tractor or somebody smoking is passing nearby. The last days we take advantage of the calm weather for clearing the garage’s roof from the huge amount of snow/ice which has accumulated over the last winter. We were moving tons of snow/ice. One block of around 50x50x50 cm of this compacted snow weighs approximately 70 to 80 kg. On Sunday I also went with Denis from the Observatory to dig a 1 m snow profile in order to better understand the snow accumulation over the winter. These measurements are needed for the ‘Hydrant’ project of the KU Leuven, from whom nobody could come this season. At such a profile one measures the temperature profile, determines how many layers are distinguishable, and within these layers one describes the ice crystals size, form and the hardness of the snow. In addition, from the layers snow samples are taken in a normed cylinder and this is weighed. This weight is then converted in water equivalent and is then used to estimate the amount of precipitation over the accumulation period. On the images, the Utsteinen nunatak and the station on the small Utsteinen ridge can be seen. On Monday, we got a bit more wind and this was announced earlier by the forms the clouds form over the Romnoesfjellet peak towards north, around 60 km from Princess Elisabeth station.

Late Summer

Since a few days we are enjoying very good weather conditions. The wind is very weak, clouds are few and only higher up and thin, so that there is a lot of sun. This means also that we have a lot of hot water, and there is no limit to take showers. On Tuesday, temperatures rose for a short moment even up to plus 3 (degC), caused by the insolation and no wind. The next day, this was not reproduced, only because there were little more clouds, and temperatures stayed around minus 10. This year’s summer season reaches slowly its end. This is marked by the circumstance that during some night-time hours it becomes now distinctly darker. At the moment this is approximately between 22hr to 02hr local time.

During the last days I had time to service some of my instruments and to do some tests, e.g. that the necessary flows needed to get the particles from outside through the tubing to the instruments are correct, or that the particle counter has no or a negligible background count (by putting an efficient filter in line). And as one part of the current team, including me, leaves already coming Tuesday the station, I have to think about to prepare the instrument staying over winter accordingly. Also everybody else is already busy with phasing in into winter mode. E.g., some parts of the water treatment unit have already been shut down because the cleaning and emptying can take days, or the power system undergoes more tests to be prepared for winter mode operation.

Work and Weather

Last days we had two minor storms, the first on Thursday and the second on Friday to Saturday. They were not really strong, but strong enough that the Utsteinen Nunatak was barely or not visible anymore. On the bottom photo you can imagine the snow drifting or blowing across the ridge on which the station and the aerosol instrument shelter is located. When the visibility becomes bad like this, you better stay inside and only the really necessary and essential tasks outside can be done. On Saturday morning already, wind became less, and around noon wind was weak and we had a nice sunny day again. It is fascinating to watch then how the wind has formed the snow and ice surface. You can easily walk a long time around, just watching the ground and the diverse shapes the storm has left. Today, there is a cirrus stratus layer above us and a nice Halo could be seen (top image). This optical phenomenon is caused by the refraction of light, under a certain angle, on ice crystals within these clouds.

On Saturday, I installed the last instrument I brought with me – an ultrafine condensation particle counter. This instrument measures how many particles there are in the atmosphere, from the very tiny ones to coarse particles. For an atmospheric researcher like me, very tiny means around a few nanometres (that is one billionth of a meter), and coarse would be a particle of 2 or 3 micrometres (what is in fact still very small). For comparison, a typical cloud droplet is around 20 micrometres and a rain drop about 2 millimetres. With all aerosol instruments now running, we have a comprehensive description of the physical and optical properties of the atmospheric particles in this part of Antarctica. It is now the aim to let as much as possible of all the instruments running over winter. Therefore, I will do some checks and preparations with the instruments in the coming days.

The first week at Utsteinen

It is already one week since I’ve arrived at Princess Elisabeth station. We had exceptionally calm weather the whole time, wind has been a scarcity until now. And we are spoilt with sunny weather. The temperatures are between minus 8 to minus 16 around the station. A bit further away from the station, temperatures can be markedly colder. Utsteinen is thus often protected by the surrounding Sor Rondane Mountains against the catabatic winds. The temperatures we encounter here do certainly not make an impression on all of you in cold Belgium or Germany. Yesterday we had a nice view of full moon, the clouds disappeared in time. The next days we will get more clouds and wind and probably also a storm. How intense it will be – we will see. Anyway, the exceptional quiet days will be over.

In the meantime, I installed two new instruments in the southern shelter – a nephelometer (measuring the dispersion of light by ambient particles), and a laser aerosol spectrometer, detecting the size of the ambient aerosol particles with the help of laser light which is scattered by the particles in an optical detection chamber. On the bottom image, the aerosol spectrometer is in the middle and the nephelometer on the right (on the left the aethalometer, measuring the absorption of light by the ambient particles). One application of the instruments is the direct measurement of the so-called single scattering albedo. This is a parameter expressing the relation between the absorption and the dispersion of sunlight by the aerosol particles. It expresses how much radiation from the sun is reflected back to the top of the atmosphere (cooling thus the surface) and how much is absorbed by the particles (the absorbed radiation is then radiated back by the particles to the surrounding atmosphere, heating it) – is widely used in models simulating the radiative impact of aerosols.

Thanks a lot for all the comments you wrote already. It’s nice to have such a quick, smooth platform to exchange thoughts between Antarctica and Belgium.