Thursday, 3 September 2015

Record for duration of data time series

We are now in September, this means deep winter in Antarctica is over and more and more sunshine is coming back. There is already more than 10 hours sunlight per day at Utsteinen. And the instruments are still operational, without any break since the last team left Utsteinen in February !! This means a new record. The longest period for continuous aerosol data until now has been from November 2013 until the morning hours of 1 September 2014. This is great news and many thanks have to go to the team members who prepared the station’s energy system for the uninhabited period (and who are supervising it remotely from Belgium). But it also means that our own precautionary measures for unattended instrument operation are paying out. Now let’s hope that it keeps going until another BELARE expedition team arrives at Princess Elisabeth station.
Particle number per cm3 at Utsteinen from November 2014 to August 2015
The figure shows the time series of the particle number concentration from November 2014 until end of August 2015. The data are cleared of any contamination. It can be seen that from November to March the mean concentration was around some hundreds of particles per cm3, with a peak around end of February/beginning of March. The mean number concentration decreased afterwards to reach a minimum in June, July. In August, number concentrations started to increase again. During June and July, the number concentration fell to some tens of particles per cm3. During austral winter, the Antarctic vortex, the atmospheric circulation, forms a quasi-barrier for air masses from lower latitudes. Also during winter, there is hardly any sunlight for driving photooxidative aerosol chemistry and there is a general lack of precursor gases for new particle formation and condensational growth of particles. However, over the whole time period, there were several events, when the number concentration increased distinctly over very short periods of time, often to some thousand particles per cm3. Most probably, these periods reflect the influence of air masses transported to Princess Elisabeth station via synoptic scale events (cyclones, transporting air masses from easterly directions, including maritime origin), indicate entrainment of air masses from the higher troposphere, or indicate periods when new particle formation could be detected at PE.

Friday, 27 February 2015

All under remote control

Time has been flying and in the meantime it is end of February 2015. Princess Elisabeth station is uninhabited since two days. During the past two months, Johnny, the station’s main engineer, took care of our instruments and also of the balloon radio soundings. All instruments have been operating fine, including the sunphotometer. At the very last days of Quentin’s and my stay we managed to get the sunphotometer operational. It appeared to be an ordinary power issue – a loose contact at the battery. It is very good that this instrument has done measurements now for two months – for the vast Antarctic continent there are very few of its kind installed, although its main output, the aerosol optical depth (AOD) is a widely used parameter in global chemical transport models. Our other problem child, the size distribution instrument, had itself no failure. But, unluckily, during a storm in mid-January very little snow intruded into the aerosol measurement container, however, exactly onto the laptop which was used for that instrument. Snow smelts and thus the laptop broke… Nevertheless, help arrived with a feeder flight beginning of February. That flight brought in Stephan Bracke from RMI’s department in Dourbes. He came for installing new instrumentation for Geomagneticobservations. But he also brought with him a new laptop for running the aerosol size distribution instrument. So, we were lucky to have at least a total of 6 weeks of data from this instrument. At the end of the season, Johnny dismounted it and it will be repaired and calibrated in order to be re-installed during summer season 2015-2016. Like this instrument, also the Cloud Condensation Nuclei counter (CCNc) of TROPOS (Leipzig, Germany) and the sunphotometer will be shipped back. The sunphotometer will undergo its yearly calibration (in addition, there is hardly enough sun for it during winter) and the CCNc will be used for other measurement campaigns (and hopefully will be back next season). The Brewer ozone spectrophotometer also has been dismounted. It could continue with its measurements automatically, however, its mechanics and optics are very sensitive. If anything happens during the winter months – there is nobody to quickly stop it or repair it – and the risk is too high that this very expensive instrument encounters serious damage. It is stored safely in PE until next season. The ground equipment and antennas for the radio soundings are also shipped back to Brussels. We want to compare some of these radio sondes with the radio sondes type we are using operationally in Brussels. This will help to raise the confidence and accuracy of the radio sondes’ data. Altogether, this meant a lot of dismounting and packing work for Johnny. And a lot of cargo-customs-paper work for me. Now, there remain four aerosol instruments operational – the TEOM-FDSM, the aethalometer, the nephelometer and the condensation particle counter. At this place I want to express my gratefulness to Johnny who took great care of all the instrumentation! Now lets keep fingers crossed that everything goes well down there in the Antarctic.

Monday, 15 December 2014

Works are going on

We are not only busy with instruments directly at the station. We also went to the automatic weather station a few hundred meters to the East of the station in order to maintain it. Its data logger was partly damaged in mid-June during heavy winds (up to 26 m/s). We had a new one with us and replaced the old one with the new one. Parts of the measurements of that automatic weather station are temperature sensors in the ice for a vertical temperature profile. As there is every year some snow accumulation (some years more, some less, with a high variability), these sensors are not anymore at their original depth and therefore new ones are placed. If possible, the old ones can stay connected to the data logger. Another important piece of information for the interpretation of snow accumulation comes from snow profiles, i.e., the digging of a pit/hole of around 1.5m depth. One determines the different layers of snow (e.g., hardness, crystal size, form), measures temperature, ice crystal habits, and takes measures for deriving the water equivalent in mm of the different layers. Quentin and I went to dig such a snow pit on a calm sunny day and the views one has are really beautiful. The snow knife is necessary to cut out the cylinder for the water equivalent measures out of the surrounding ice.
We also continued the trials and repairs to get the laser instrument for measuring the size distribution of particles and the sunphotometer back to operation. Very likely, the sunphotometer has an issue with its motorized robot system and somehow the delicate system of gears and pins to detect zero and other pre-defined positions has been de-routed. It is still not working and we get a bit desperate on it. On the other side, we managed finally to get the laser instrument back to work. It took quite a few emails with the manufacturer and trials/repairs on the internal cabling of the electronic steering boards. It appeared that its internal pc was broken. We had to connect an external pc via a serial cable to the electronics of the instruments, got the software from the company, and after some typical trial and error work on the serial connection, the instrument measures since Sunday noon again. This is very good news. The data of this instrument are also very important for interpretation of the cloud condensation nuclei counter. So, in the evening we granted ourselves one or two glasses of fine whiskey.
In addition to this and the routine work on the other 10 instruments we launched every day a radiosonde with a balloon. If there is not much wind, it is no problem to hold the Helium-filled balloon until the radiosonde is ready (i.e. until the receiving signal of the GPS is stable). But during stronger winds, the balloon is bouncing in every direction behind our place of a container and it looks like a fight man against balloon :-)
Now we are already in our last week at Princess Elisabeth station. The schedule foresees that we leave the station on Friday or Saturday, probably Friday. This means to prepare all instruments in a way that the engineers and technicians remaining at the station can easily handle or check them.

Sunday, 7 December 2014

There is something in the air

Today on 7 December we have launched our 10th balloon with the new system and we got as usual good data on the vertical distribution of temperature, humidity, wind and pressure up to 32 km altitude (however, it needs to be said that humidity is only reliable up to around 10 km). All launches have been good until now and we are happy that we are able to create a database of the meteorological and dynamic conditions in the higher atmosphere around Princess Elisabeth station. To launch such a weather balloon it is necessary to be with two. One prepares the radiosonde which measures and transmits the data and the other holds the with Helium filled balloon until launch. At some days the wind has been very strong and it was not always easy to hold the balloon until the sonde is ready and is fixed to the balloon. During strong winds at launch time, the balloon bounces back and forth and tries to escape …
All the instruments we have set up are used to follow the evolution of aerosol (particle) properties around Princess Elisabeth station. Most of the time the conditions are relatively constant and not much special is happening. But, yesterday – we went to check routinely our instruments – we saw that the particle concentration was increasing. From the normal baseline of 200-300 particles/cm3 during summer it went suddenly up to 6000 / cm3. It happened during strong winds from eastern directions and contamination by the station can surely be ruled out. It is more probable that this was linked to the approaching of a major cloud system. The lower cloud level was decreasing when the particle concentration went up. When the concentration reached maximum and thereafter, the cloud level was increasing and the clouds even move away. The instrument from Leipzig told us that the concentration of particles being able to form clouds has not much increased during this event. So, there are some questions for us to be answered, how clouds, the whole lot of particles and particles, which can form clouds, are linked. That’s why we are here. This morning the concentration of particles was again at the usual level around 300 / cm3. And no strong winds anymore.

And, yes, also in the far region of Antarctica, St Nicolas does not forget the well-behaved.

Monday, 1 December 2014

Instruments back to operation and Antarctic Day

On December 1st, the Antarctic Day is celebrated. On 1 December 1959, the international Antarctic Treaty was signed by 12 nations (inlcuding Belgium). The treaty set aside the vast Antarctic continent exclusively for peaceful purposes, serving the interests of all mankind. The Antarctic Treaty became the first institution to govern all human activities in an international space, i.e., a region beyond sovereign, national jurisdiction. Each year the parties to the Antarctic Treaty gather together to discuss any issues, e.g., related to Antarctic tourism, environmental protection or best-practices in operating research stations. Today, around 30 countries are full members to the Antarctic Treaty. Celebrating Antarctic Day each year was initiated on the occasion of 50 years of the treaty in 2009. For example, school classes have been working before on the thematic of Antarctica and then sent their drawings with researchers or staff to Antarctica. These drawings are then mounted, displayed, or similar (depending on weather and wind conditions) at several research stations. There are also many chats via skype of school classes with researchers or staff people, bringing daily life of Antarctica nearer to the public. Also at Princess Elisabeth station several skype sessions were organized, including one with me with a primary class in the UK. It was both fun for them and me.

On instrument side we have not been lazy in the meantime. Quentin and I set up nearly all instruments. 6 instruments in our little container for measuring characteristics of atmospheric particles, 5 instruments on the station’s roof, which will measure total ozone, UV radiation, attenuation of light by particles, cloud and precipitation characteristics. More information on these instruments can be found here. One instrument in the container is not starting up anymore. The reason is not absolutely clear at the moment, but it does not look good. We also have some trouble with our loved sunphotometer robot on the roof. It should track the sun for its measurements. Although we tried hard to mount and orient it correctly, it prefers to point either in the morning or in the afternoon some azimuth degrees aside of the sun. As it has been very windy yesterday and today (up to 12 m/s), we have not been able to do more trials. So, the sunphotometer is waiting for the next fair weather day for further servicing. Setting up the ozone spectrophotometer allows us to follow the evolution of the total amount of ozone over the whole atmospheric column. Actually, a remainder of the yearly ozone hole is partly moving above our region of Antarctica. Therefore, total ozone is reduced and ultraviolet radiation from the sun is increased. This UV radiation can cause skin cancer and therefore it is important to protect yourself, even if we have only small parts of our skin exposed freely. I put a graph of the UV index on 26 November. It reached very high values around 9 that day, meaning that unprotected skin will be burned in around 15 minutes. 

Quentin and I installed also a new system for the launch of radio sondes. These sondes will measure temperature, humidity, wind and wind direction and pressure up to around 22 km. These data will give more information on the dynamics of the atmosphere above us, on transport processes, and will also serve forecasters and modellers of the weather in East Antarctica. Our goal is to launch each day one balloon. The image shows Quentin just launching a balloon yesterday at very windy conditions.