Being back and staying connected

It’s now already six weeks ago that I left Antarctica and that I am back in Belgium. Normal working life takes over rapidly. It has been time for debriefing meetings, for securing the data and to proceed to first preliminary data analysis, but also to think already what tasks have to be done during next season and what this means with respect to sending staff and cargo.

From the Belatmos instruments, three of them are still operational – the aethalometer, the TEOM-FDMS, and the laser aerosol spectrometer. The aethalometer and TEOM-FDMS are storing the data on their internal data storages and will be read out next season. Concerning the aerosol spectrometer – it is connected via an Ethernet cable to the internet. Therefore, I can regularly check the size distribution data and also download the current data. This also means that at this moment, the power supply of Princess Elisabeth station is still working. Let’s keep fingers crossed.

Above, I put some preliminary plots with examples of aerosol data. The top image shows the total scattering coefficient measured by the nephelometer at 635 nm for roughly two days (of 5min average data). These coefficients are given in units of Mm^-1 (or 1*10^-6 m). The scattering coefficient correlates well with the overall amount of ambient particles – the more particles there are, the higher the scattering coefficient. However, at the same time, aerosols do scatter and absorb, and the more scattering compared to absorbing they are, the higher the scattering coefficient will be. Values like shown in the graph represent low overall aerosol concentrations.

In the middle graph, the total number concentration detected by the condensation particle counter (CPC) is shown for two hours (1min averages) from the same period. The overall particle concentration was around 600 to 700 particles per cm-3. The few much higher peaks indicate very probably the measurement of the exhaust of skidoos or prinoths passing by nearby. However, this has to be analysed and confirmed in more detail. As mentioned in a former post, the usual concentration in sub-urban regions would be 10 to 100 times higher.

The bottom image gives the number size distribution over the two hours of the total number concentration of the middle graph. Although the laser aerosol spectrometer can only measure from a particle size of 90 nm onwards, the dominant size around 100 nm was within the measurement range. It also can be seen that there are hardly any particles larger than 1 micrometer. In a further analysis, I will combine the two measurements of total number concentration and of size distribution to define the concentration within the range 3 to 90 nm – as the CPC is measuring all particles from 3 nm onwards.

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.