The last days

Now my stay at the Princess Elisabeth station is almost over. Tomorrow, Tuesday, we will fly around noon with the ‘Lydia’, (the plane we also came here) to the Russian air base Novolazarevskaya near the coast. There we only have a few hours before the large Ilyushin 76 will fly us to Cape Town in South Africa. About 12 of our team will leave Utsteinen and in Novo we will join other Antarctic expedition members from Germany, Norway, Sweden, Japan to fly together back to Cape Town.

Last Thursday and Friday we had a storm here – not of the worrying type, however, the wind speed was 15 – 17 m/s at the weather station 300m to the East. So, on our ridge, the wind speed was probably higher by about 4-5 m/s. There was a lot of drifting or blowing snow, from times to times accompanied by real snowfall and the visibility was really bad – the Utsteinen nunatak was for a long time not visible anymore. Now that the summer season reaches slowly the end, also the sun sets deeper and deeper behind the mountain ranges in the south. At some days this leads to nice views around midnight. This mountain range also influences strongly the upper air flow and sometimes we can watch the formation of large, impressive, cylindric clouds.

The ozone spectrophotometer which is installed now on the roof of the station is doing nice measurements. Besides the total column amount of ozone in the atmosphere, we can now also derive the UV index for Utsteinen, i.e., a measure of the probability of ultraviolet radiation induced erythema of different human skin types. On 23 to 26 January, on rather sunny days, the UV index reached up to 6, indicating a moderate intensity at which the skin burns easily. On the days of the storm, with a complete overcast sky, the UV index reached nevertheless 5. This only slightly lower index is caused by the very low and thin clouds, through which the shortwave radiation can easily penetrate.

Up there in the air

The days of last week passed by with a very cloudy sky and with strong winds. The strong winds and dynamics in the upper troposphere can nicely be observed in the cloud formations. Over the nearby Sor Rondane mountains, there are now most of the time quasi-stationary mountain wave clouds. It is interesting to watch that other cloud layers move with the general wind directions, but these mountain wave clouds stay more or less always at the same place, i.e., that the advected air masses are lifted up at this region, cool down, form clouds, and then they are, like in a wave, transported downwards where they warm and do not form a cloud anymore. However, this region in the lee of the mountains where it is cool enough for cloud formation, stays more or less stationary, and the air masses are transported through it. So the cloud forms steadily new, but it seems as if it is not changing. A very similar cloud type are the lenticularis clouds, which form in a similar way and which we can observe here now every day. The image above gives a nice example of such clouds. In addition, the sun is now longer times hidden behind the mountains during midnight hours and the horizon then shows violet to red glow. Saturday night when there were less clouds, the moon could be seen.

The Brewer ozone spectrophotometer is now finally installed and fixed to the roof. The first good measurements were possible this Sunday, as we had finally a sunny day and the instruments makes best measurements when there are no clouds before the sun.

Since a few days the Princess Elisabeth station has been the base for some scientific flights with the Polar-5 in order to investigate the magnetic field of the Earth. Detleff from the German Bundesanstalt fuer Geowissenschaften und Rohstoffe and Daniel from the German Alfred Wegener Institut (AWI) and the pilot crew of the Polar-5 have been flying with this aircraft of AWI over the mountains and adjacent glaciers of the Sor Rondane mountains. With the maps of the magnetic field of the Earth made with the instruments installed in the Polar-5, they can derive informations on the tectonics of the Earth’s crust mantle and on the directions of cracks in the tectonic plates. The Polar-5 is a transformed DC3, adapted to the conditions in polar regions.

Finding the right orientation for the ozone spectrophotometer

During the last week, we installed the Brewer ozone spectrophotometer on the roof of the station. As already explained in the last post, this instrument will serve to monitor very precisely the amount of total ozone in the atmosphere. It will not only help to monitor the evolution of the ozone layer, but it will also be valuable to validate satellite measurements of the ozone amount. The retrieval above highly reflective areas like the Antarctic is not always easy and therefore ground-based measurements are important.

In order to do its measurements, the ozone spectrophotometer turns with its optics always towards the sun. This is not that simple as it sounds. One essential parameter is the azimuth angle. This angle is defined as the angle between the North and clockwise going to the position of the sun. In the northern hemisphere this angle starts at 0 degree in the North and goes over 90 degree East, 180 degree South, 270 degree West back to 360/0 degree North. On the contrary, in the southern hemisphere the azimuth starts (as the definition stays the same, but the sun moves from East over North to West) with 180 degree in the South, goes back to 90 in the East, to 0/360 in the North, over 270 degree in the West back to 180 in the South. As the suntracker of the Brewer with its motor system is able to do one clockwise rotation of 360 degrees and then turning back to its starting position, the tricky thing with orienting the Brewer in the Antarctic arises with the transition point around local noon when the azimuth makes a jump from 0 to 360.

After some tests in order to find the correct positioning I found two possible solutions with the great help from Hugo in Brussels and Arjan in Delft. One possibility is to orient the tracker as in the northern hemisphere with its zero point to the North. At local noon, at the switch from 0 to 360 degree, the tracker makes a full 360 degree rotation. This setup has the disadvantage that there is some time lost due to the tracker’s rotation. And this just around the short precious time when one can get the best measurements in a place like Antarctica with its (mostly) low sun elevations. The other possibility is, to orient the tracker with its zero point to the South. However, as the software calculates the correct azimuths (starting at 180, not at 0), and the tracker counts its degrees clockwise, one has to set an internal offset of +180 degree. For the azimuths when +180 and the azimuth results in more than 360 degree (and, as the tracker’s rotation is limited to 360 degree), the tracker internally knows that it cannot move clockwise more than 360. So, it subtracts automatically 360 degrees. In this setup, it does not need to make a full rotation around local noon. This full rotation is then done around local midnight, when the sun is anyway too low for measurements.

Besides the instrument installation, there are many opportunities to make some nice photos of the clouds and the landscape here. Above, I put some new ones.

The measurements

During the last week the measurements with the TEOM instrument started up. This instrument measures the aerosol mass concentration. It can be combined with special inlets which allow only specific aerosol sizes to enter the instrument. We are interested only in the smallest particles, below 10 micrometer or smaller and one of the images shows such an inlet. The TEOM measures the mass concentration with the help of an oscillating microbalance on which a special filter is mounted. The mass which is deposited on this special filter is measured via the changes in frequency of the oscillation of this microbalance. This kind of instrument is commonly used to measure the particulate mass concentration of fine dust in Europe or North America. Here, in the Antarctic we are not expecting high levels of the mass concentration. It is the aim to monitor this concentration over a long period in order to be able to detect if there is a change or trend in the concentration or not. If there is any trend, this would, e.g., indicate a change in the long-range aerosol transport or global circulation patterns. The image with the graph gives preliminary results of the first measurements of the aerosol mass concentration at Utsteinen.

In the coming week I hopefully will install the Brewer ozone spectrophotometer on the roof of the main station. The image shows me in front of this instrument. It will measure the total amount of ozone in the atmospheric column above us. For final installation it needs a very robust fixation to the rooftop. To monitor the ozone column amount in Antarctica is important because above Antarctica the ozone hole is still very large every year and the more spatially distributed precisemeasurements there are, the better a recovery of the ozone layer (what is expected to begin in the coming years) can be detected.

Besides our atmospheric composition measurements there is also research done on the biodiversity of life around Utsteinen, in particular species like cyanobacteria and lichens. This season, Zorigto Namsaraev from the University of Liege joined the expedition team (see also his blog antarcticabelgium.blogspot.com). He found already very interesting samples and it is possible to watch them under special microscopes. This brought us to the idea to put, just for curiosity, a used filter sample of the aethalometer under such a microscope. Soot or Black Carbon particles (what the aethalometer is for) are normally of the size of a few nanometer, maybe up to 200nm. Normally, for making nice images of these particles, special high tech microscopes are used, not microscopes for microorganisms of micrometer size. However, the image posted here shows besides the interesting aethalometer filter matrix a few dark spots, and these are very probable soot or black carbon particles, agglomerated together. Of course, I took a dark filter sample from the few days when the aethalometer sampled air enriched with exhaust particles from the tractors, skidoos or generators. Normally, the used sample spots are quite white and it would be very difficult to find traces of black carbon particles.

2011 has begun

Since a couple of days we have strong wind from eastern directions now. Over the ridge the snow is drifting and there are more and more clouds. On Friday 31 December there was even light snow fall. Since Friday the sunphotometer cannot make useful measurements because of the many clouds. The nice image of the sunphotometer with the halo was taken by Stefan Kneifel from the University of Cologne. For the aethalometer on the other hand, the steady winds from eastern directions are very good because in this way it measures the pure Antarctic air – the concentrations of pollution aerosols are around the detection limit – and this is what we are expecting. If we are able to operate this instrument over several years it will be possible to see if there is a change in the concentration level. In the case when the wind becomes weak, the influence of the station is immediately seen. If in addition tractors, generators or skidoos are in operation, the amount of combustion particles the aethalometer detects is then of the same order as in suburban areas in Europe. The TEOM, which you can see built up in the shelter on one of the images, will give information on the mass concentration of all particles, not only the pollution aerosol particles.

New Year’s Eve and New Year itself were quiet days. For New Year’s Eve David, our cook, created again a delicious meal and we were sitting together this evening. The beginning of the new year we welcomed with champagne or wine. It is however difficult to have this feeling that a new day or a new year is starting. With the sun shining whole day round and in particular coming out behind the clouds at midnight – I did not have the impression that this moment was special. This is again an example that it is important to structure the days in Antarctica, otherwise you loose any feeling if it is now day- or night-time.

For the time being we are only 17 left at the station. The other 11 team members are with the meteorite seeking expedition. They went last Thursday with three tractors to the ice plateau, almost 3000m high and about 70 km away. 5 will stay there for three weeks, the others will return today or tomorrow. The weather conditions are harsher than at Utsteinen – with around 1500 m higher temperature will be at least 15 degC colder (but often even more ), wind is stronger, and the height is an additional issue (you have to breathe more, the tractor motors are getting problems…). In the meantime we occupy ourselves besides the normal duties also, e.g., with shoveling snow from the roof of the stations annex buildings, which is blocking some solar panels or creating too much weight for the roof.