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).

The BELATMOS measurements have restarted

Since mid-November Princess Elisabeth Antarctica is again operational. On the special website of the station (www.antarcticstation.org) you can follow the story. Erik, the engineer also responsible for taking care of the scientific equipment, restarted our instruments already. The TEOM-FDMS, the aethalometer, and the Brewer ozone spectrophotometer are operational again. The TEOM-FDMS and the aethalometer collected data also during winter, at least as long as electricity was there. This is something very interesting because the two instruments collected data when there was no station activity and when there was really no emission of aerosols for energy generation (only wind power and batteries). Data of this kind is rarely sampled in Antarctica. In one of my next posts I will tell a bit more about these data. The forth instrument, the Cimel sunphotometer, will arrive these days at the station and if weather allows, it will also be installed soon after.

The ozone spectrophotometer did already its first measurements, from 13 December onwards. On 14 and 15 December, the values for total atmospheric column ozone were really low, between 220 and 240 Dobson Units, before climbing the next days higher (see bottom image). On the image in the middle it can be seen that it fitted to the overall pattern of total ozone in the Southern Hemisphere. That image is a composite of measured total ozone values from observation stations worldwide (World Ozone and UV Data Centre), to which also our instrument contributes. The area of lowest total ozone was located on 14 December over East Antarctica and Dronning Maud Land. The black spot depicts the approximate location of Princess Elisabeth station. The upper image shows the UV index for that day. It is very high to extreme around local noon. These high UV values can be explained by the low total ozone values, the elevation of the station (1400 m) and the almost aerosol free atmosphere. They are also particular because the elevation of the sun (elevation above horizon) is not that high, although it is austral summer and near to summer solstice – on 14 December the elevation angle reached only 41deg. This is low compared to late spring, summer in our northern midlatitudes. And then the UV index in our region only rarely reaches values of 8/9. It means that the sun poses really a danger in Antarctica. Although the ozone hole period is over now in Antarctica, there are still large areas with low total ozone values, as can be seen in the middle image.

Merry Christmas and till soon

Next austral summer season about to begin

The next Belgian Antarctic expedition is about to begin. The first team will leave Cape Town mid November 2011. This season, I will be again part of the expedition team, however, this time towards the end of the season, from end of January to 21 February 2012. Nevertheless, there are many things to prepare right now.
Unfortunately, the power supply system of the station broke down beginning of Antarctic winter. This means that the first team arriving at the station will have to take care of a lot of extra things, and also to take care of the two Belatmos aerosol instruments – the aethalometer and the TEOM-FDMS – which are installed in the southern scientific shelter. It will have to be checked if they are in order and not damaged after the power failure and the long winter-over, and before a re-start they have to be warmed up slowly.
Engineers of the team will also take care to re-install the AERONET Sun photometer and the Brewer ozone spectrophotometer on the station roof. As they need sun for their measurements, they cannot measure during the dark winter months and only with arrival of the first expedition team, they can be re-installed. In addition, the Sun photometer has to be calibrated in Europe annually and travels therefore each season back and forth.

When I will be at the station, I will bring with me 4 new instruments, measuring UV-A, UV-B and total solar irradiation, aerosol total number concentration, particle number concentration in several size classes, and spectral scattering of the aerosol particles. I will give here a brief description of these instruments:
The Ultrafine Condensation Particle Counter (U-CPC) measures the ambient aerosol number concentration from 3nm to 3 micrometers diameter. It will be installed in the same container as the aethalometer and the TEOM-FDMS.
The Laser Aerosol Spectrometer (LAS) measures the aerosol size distribution in the diameter size range from 90nm to 7.5 micrometers (size classes can be adjusted). It will be installed in the container with the other aerosol instruments. A year-round operation is envisaged. The difference of the number concentration of the U-CPC and the integrated number size distribution of the LAS (90nm to 3 micrometer) will give an estimate of the nucleation and Aitken mode aerosol concentration (particles smaller than 90nm).
The 3-wavelengths nephelometer will measure the total scatter and the backscatter at 450, 525 and 635 nm. As the nephelometer will be installed in the same container like the aethalometer, they will probe the same air mass and therefore, a direct measure of the single scattering albedo will exist (ssa = scatter / (scatter + absorbtion) ). The single scattering albedo is an important parameter used in radiative transfer algorithms in satellite retrieval algorithms or in climate models
The irradiation sensors will be an UV-A radiometer (315-400nm), an UV-B radiometer (280-315nm) and a pyranometer for total solar irradiation (305-2800nm). The sensors will be installed on the roof of the station and year-round operation is envisaged.
In summary this means a lot of work, but all the instruments together will provide very nice data sets describing comprehensively the aerosol composition, UV radiation and total ozone at Princess Elisabeth station.

Something NEW: The COMMENT function of this blog should now work much better than before !

Nobody there, but

In the meantime, the BELARE 2010-2011 campaign has come to an end. The last team left on 24 February Utsteinen. They prepared the station for the winter conditions. Two of my instruments, the aethalometer and the TEOM-FDMS were left in operation mode in the southern scientific shelter. This is kind of an exciting test. First, there is no communication connection to this shelter yet, so we do not know really what is happening in there and if the two instruments are working. Second, aerosol measurements like this in Antarctica are usually done at locations where year-round maintenance is possible. Third, everybody is hoping that the power will be available the whole winter through. Taking all this into account, it will be a unique dataset if everything works out well and if we can retrieve the winter data beginning of next summer season.

A very good estimation if everything is ok is the knowledge about the power management system and if other instruments at the station, which are already connected to the Internet, are still working. If there is enough power available at the station, there is also power at the southern shelter as it is on the same power priority level. And as the aethalometer and TEOM-FDMS are robust standard monitoring instruments, there is no need for an increased concern. Until today there has not been a problem yet with the power provision at the station. However, as wind has been low at many days, apparently the diesel generators took over during periods of low winds.

At our institute, Andy has written a small programme that creates a so-called Ensemble Prediction System (EPS) forecast for Utsteinen (better: the nearest model grid point). Such an EPS takes meteorological analysis data from the European Centre for Medium-Range Weather Forecast and makes 10-days forecasts (see image above). The specialty of the EPS forecast is, to run the same model 50 times, but each with slightly different initial conditions, representing model uncertainties. The result is a probability distribution for the meteorological forecast values, giving medians, percentiles and extreme values. A narrow distribution for a parameter shows very good confidence in the value, and a broad distribution illustrates higher uncertainty.

We compared these EPS forecasts to measured values from the automatic weather station and it appeared that the tendencies for wind speed and temperature are very good. Wind speed is most often a bit overestimated and temperature mostly too cold – probably due to the unique setting of the station protected by the Sor Rondane Mountains, which cannot be resolved by the model. Although clouds and precipitation are very difficult to simulate, the EPS forecasts are useful the first few days for cloud coverage. Precipitation is most often largely overestimated. When I was at the station, during most predicted snowfall events, precipitation was detected by the instruments of the HYDRANT project able to measure cloud height and falling crystals or droplets. However, this precipitation mostly never reached the ground or it was much less than predicted. This is a phenomenon we want to investigate further, e.g., with additional monitoring instruments or with profile information on temperature, humidity and wind.