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.

Arrival in Antarctica and at Princess Elisabeth station

I am back now at Princess Elisabeth station since last Wednesday, 01 February 2012. Our flight from Cape Town to Novolazarevskaya runway station took place as scheduled in the night from 30 to 31 January. After 6 hours in the Russian Ilyushin 76TD, we landed on the 3km long runway of ice with a bit snow on it. Our team of 3 scientists (Elie from Ghent University, Denis from the Royal Observatory, me), Jan, the medical doctor, and Diego and David as camera team for National Geographic and French Canal+ had then to wait one day before the feeder flight to Utsteinen and Princess Elisabeth station with the Basler could take place because of bad visibility and slight snowfall at Utsteinen. You can see the two aircrafts on the bottom image, the Basler in the front and the Ilyushin in the back. So we spent the day and a night at Novo. There is not much to do there, most of the time we took a sieste, interrupted by breakfast, lunch and dinner. Our feeder flight to Utsteinen was then at 5 in the morning (7 am Belgian time), carrying us 6 and our scientific cargo and food for the station. After 1 ½ hours we arrived at Princess Elisabeth station, with fair weather and the station team welcoming us. The aircraft was unloaded and again loaded with the cargo for the people leaving the station, mainly German geologists and geophysicists with many boxes full of … stones :-).

It is a good feeling to be back again. The circumstance that it is already the third time for me to be at Utsteinen makes everything feeling familiar. However, coming to Antarctica is always very particular, and the special atmosphere of Antarctica with its vast spaces of ice and snow and sometimes rocks looking out, the remoteness, and the purity, leaves every time a new big impression. Also the station itself is nice to see again. The second image from below shows the big satellite dish and the wind turbines. Now in February, the sun is hidden longer and deeper beyond the horizon and the Utsteinen mountains to the South. Therefore, during some ‘night’ hours the light becomes now dampened (see second image from above), but it is not becoming dark yet.

After breakfast, there was the general briefing and then there was time to get organised ourselves. I had first looks at my four installed instruments. Everything looks fine and the last days I made several checks and controls and retrieved data. The Sun photometer (third photo from below) on the station’s roof top is doing its familiar turns, pointing to the sun, as is the Brewer ozone spectrometer. My next steps will be to get the new instruments to the aerosol shelter and to install them. In addition, I will maintain the automatic weather station, not far from the station (third image from above). Yesterday, I went already there to take photos of its state and to make some checks. I went there by bike (upper image), really zero emission. Somebody from Belgium built this bike and asked if they would like to try it at Princess Elisabeth. So, it is here now and everybody has fun with it, and if the snow is not too soft, it is easy to cycle with it.

First BELATMOS winter aerosol measurements

As mentioned in the blogpost before, the TEOM-FDMS and the aethalometer collected data during last winter, at least from end of February to mid of April. This is something very interesting because the two instruments collected data when there was really no emission of aerosols for energy generation (only wind power and batteries) or from station operation. This makes them valuable data with information on real background concentrations. In addition, these data are special because they were sampled without any direct maintenance/attendance of personnel. Measurements in Antarctica with these kinds of instruments are done normally at stations with overwintering personnel. The data I am reporting here are nevertheless preliminary and several quality assurance steps have to be applied. This is in particular important because the TEOM-FDMS and the aethalometer are measuring near their detection limits.

The average of the total aerosol mass concentration measured by the TEOM-FDMS was 0.85 microgram per cubic meter with a standard deviation of 1.03. For the moment slight negative values are still accepted because of the general low aerosol concentration and because of the detection limit of the TEOM-FDMS, which is around 1-2 microgram per cubic meter. I have to make additional checks to justify if negative values are skipped or not. For the winter 2011, 12% of the data are negative, but almost all just between 0 and –1.0 microgram per cubic meter. That the standard deviation is higher than the average means that the average total aerosol mass concentration was not – from a statistical point of view – different from zero, neither definitely positive of negative. To be able to determine this further, a longer time series will be necessary. Another possibility is that the integration time for determining a TEOM-FDMS sample would have to be longer (meaning more mass sampled on the filter before the data value is taken). However, I set the integration time already to 2 hours.

Another possibility is to cross check the TEOM-FDMS data with data from the other aerosol instruments. However, the aethalometer measures the strong absorbing particles, amounting only to a small part of the total aerosol mass. The arrival of the new instruments this season will provide more insight. In particular the Laser Aerosol Spectrometer measuring the size distribution could prove valuable to check the aerosol mass concentration measurements. By integrating over the number concentrations of all measured size classes, and assuming a certain mass density of the particles and a certain shape, it can be cross-checked if either data is reasonable. The winter aethalometer data shows an average of 5.2 nanogram per cubic meter with a standard deviation of 5.4. This means that we are really measuring near the detection limit and a longer time series is necessary to be able to make statistically sound statements how much absorbing particles (or black carbon) there are in Antarctica. However, concentrations between 0 and 10 nanogram per cubic meter would be the expected level.

The images above show the state of the shelter for the aerosol instruments after the winter (no power, heating for 7 months), after cleaning and letting it dry, and an image of the interior of the aethalometer. It shows the filter tape on which the samples are collected. On the right one can see some darker spots. These are the old samples, and the tape is drawn further when a certain absorbance is reached. The snow and ice inside the shelter freightened us a bit if there was damage to the instruments. But it appeared that this was not the case, luckily.

The departure for this season's expedition comes nearer. I will fly this Friday from Brussels via London to Cape Town, South Africa, and the flight from Cape Town to Antarctica is scheduled for Monday evening. So, the next news will come from Antarctica (or from Cape Town, if the weather conditions delay the flight to Antarctica).