Winter season 2013 has started

After the last team left Princess Elisabeth station (visit the station blog  antarcticstation.org), the station and also its scientific instrumentation is now completely in automatic and remote control mode. Until now, all instruments have continuously been working and are doing this also right now. The sunphotometer and the Brewer spectrophotometer however, have been dismounted end of February by Erik. The sunphotometer travels back to Europe for the yearly calibration and the Brewer is stored inside the station. In principle, it could be operated continuously, but as its optical part is very sensitive it would be too risky to leave it running. If anything happened to the instrument’s mechanics or optics, there would be nobody to repair it. This will possibly damage the whole instrument and repair or replacement would be an immense cost. All the six other instruments will continue to record and send data, as long as there is no power break down or failure of an instrument part. In the southern scientific shelter, the five aerosol instruments (TEOM-FDMS aethalometer, nephelometer, laser aerosol spectrometer, condensation particle counter) are now in their forth month of simultaneous operation. The condensation particle counter has got his larger reservoir for n-butanol supply during the long winter period, and the nephelometer has been calibrated a last time before the end of the season. Such a calibration is done with a pure reference gas, in our case extremely pure carbon dioxide. The amazing thing of remote control is that I could do some nephelometer calibration from my desk in Brussels. This needed of course some cooperation with Erik at the station who opened the gas bottles and some valves, but the exact calibration I controlled via remote desktop connection to the controlling desktop in the shelter which in turn is connected via a serial port to the nephelometer control port. As it is too risky to leave an open gas bottle nine months unattended, a full calibration will not be possible anymore. But a so-called zero-check (with ‘zero’, filtered air via an internal filter) of the calibration regression can always be done remotely. In the next entry to this blog I will show some exemplary graphs of the aerosol data. The images above show the instruments at the end of the season: the Brewer spectrophotometer and the elevated box with sensors for total solar and UV-A, UV-B irradition on the northern station roof; the Cimel sunphotometer; and the five aerosol instruments in southern shelter (order from left to right like mentioned above).

Preparations before Departure

During the last week of my stay at Utsteinen consisted mainly in checks that all instruments can operate continuously and via remote control. E.g. the condensation particle counter uses n-butanol in its measurement chambers in order to grow the particles to sizes which then can be easier optically detected. The instrument has a reservoir of 1 liter. For atmospheric conditions like suburban regions, this amount is sufficient for 1-4 weeks. In the Antarctic clean air, it will be sufficient for several months. However, surely not for almost 9 months of operation without somebody on spot who could do a re-fill. Therefore, we connected two reservoir bottles in-line, and now the instrument’s supply with n-butanol will be assured also during winter operation.

Winter operation is still two months ahead, but my stay in Antarctica ended already yesterday. Until the end of the season Erik will take care on spot of our instruments and via email and via remote control I will also stay in contact. On Friday in total 14 persons left Utsteinen (and 4 arrived new). The flight was planned for early morning, but it started to snow in the morning. On contrary to the days before, wind decreased to almost zero and low clouds moved in, reducing strongly visibility. This snowfall event delayed our departure, but it was also nice because it was again nice to see that there were specific signals around the event in the aerosol data. The snowfall was also not forecasted by the models and apparently locally influenced. However, it stopped relatively fast, sun came back and the Basler aircraft landed safely at 2pm. After unloading (i.a. fresh food) and loading and around one and a half hour of flight we arrived at 4:30pm (Belgian time zone) at Novo Air Base. The big Ilyushin carrier was planned to take off to Cape Town around local midnight. The time until then everybody used to take a nap, have a meal in the mess container or to chat with scientists from other stations, waiting also for their departure. We met again the team of German scientists who did, based at Princess Elisabeth station, many flights with the AWI Polar-6 for geophysical research. After six hours of flight we arrived this morning in Cape Town, where we now have time until Sunday evening when our flight back to Europe is scheduled. I am happy to be back, see again my family and kids.  

SNOW

Again, no report on sunny summertime, but white or grey snowy summertime. Saturday afternoon until late into the evening there was a nice snowfall event at Utsteinen. Maybe you find it bit strange that I write about snowfall when in Europe you are having also snow and even more than here. However, it’s not often that we have real snow falling here in the interior of Antarctica, and then snow is not falling in large amounts. Antarctica is a cold continent, and cold air cannot hold a lot of water vapour and therefore also the potential amount of water falling down in forms of crystals is limited. We had around 3 to 5 cm snow yesterday – what is already a lot. The whole day we had complete cloud coverage and first strong wind. In the afternoon, wind decreased to almost zero and around 5pm it started to snow. The first crystals were rather small and had the form of needles or small prisms. Two hours later, snowfall increased (also temperature had decreased a bit) and ice crystals had grown and were rather in the form of dendrites now. Our ridge where station and instrument container are placed turned slowly into white. It was interesting to follow this event with images and with the data of our instruments. I could also see in the data of the instruments measuring atmospheric particles (not snow) that some particle characteristics were different to the period before this snowfall event. For example, the size distribution and total number of aerosols changed. Today, Sunday, there is no snowfall anymore, but very strong wind and now there is drifting, wind-blown snow, and most of the fallen snow is blown and is thus re-located.

Summertime ...

During last week weather has been rather quiet. No strong winds, no storm. Pretty good for all the works which have to be done around the station. Less good for the wind power production. There were also some days with almost complete low cloud coverage and low wind, creating bad visibility and preventing our Belgian scientist team (meteorite seekers) to arrive by plane from the Russian Novo air base. At times it seemed that a bit snow might fall (low clouds and weak wind are good conditions). However, this happened not at our place but some tens of kilometers away in the Vikinghogda mountains (see images above). Two days later, we had nice sunny weather (and the scientist team could finally arrive), but these mountains were again hidden behind a wall of low clouds. On the images it looks like air masses were transported against these mountains (in fact, wind was weakly into their direction), they had to rise orographically, but then were probably trapped by a temperature inversion. Later in the evening these clouds just dissolved. On that sunny calm day there were also some nice cumulusclouds over the Perlebandet mountain ridge to the West – rather unusual to this part of Antarctica – but it’s summer here. 

On the instrument’s side of life everything goes well. I did some tests and maintenance of the aerosol instruments in the shelter. At the end of the season they have to be ready to operate during the whole Antarctic winter. And it also has to be possible to communicate with them and to control them from Belgium. On sunday I digged a snow pit, i.e. an at least 1m deep profile in the snow, in order to determine the different layers of snow/ice up to a depth of 1m. In the different layers the ice crystal habits are characterized and the snow density is measured to be able to derive the amount of snow in mm water equivalent. It was a calm, rather cloudy day, not cold, and therefore ideal to dig and to take the measurements without any hurry. Ah, and in the evening we had the first time for this season Frites (at least, it’s a Belgian station, this obliges).