From the NILU Annual Report 2017: From the Zeppelin Observatory at 79 degrees north to Trollhaugen at 72 degrees south – NILU measures air quality at some of the world’s most inaccessible places. Why so far away?
– The reason why it is so important to measure air quality in the Arctic and Antarctica is that those are the most vulnerable areas. We see changes there first, senior scientist Chris Lunder from NILU’s Department of Monitoring and Instrumentation Technology explains.
The Zeppelin Observatory near Ny-Ålesund on Svalbard, and the Trollhaugen Observatory in Queen Maud Land, is where the air is purest in the northern and southern hemisphere, respectively. This means that NILU’s scientists can measure air at what they refer to as the “background level”. The background level means the lowest level of different particles and gases present in the atmosphere, and it is only measurable in places where human activity does not contribute to local contamination. You find the cleanest air on earth in Antarctica, and from air samples taken there, scientists have the best information to say something about how the formation of particles in the air was before the industrial revolution.
– Knowing the “background level”, we can use the air samples to figure out where pollutants come from, and the amounts of pollutants released.
Showing trends over time
Greenhouse gases are mixed into the atmosphere, so there is always a certain “background level” of eg. CO2 in the air. How much higher levels can get varies from station to station, relative to local emissions and how the emissions are transported through the atmosphere.
– The advantage of remote stations like Zeppelin is that it’s easier to see trends over time there, because the variation from month to month is smaller, explains senior scientist Ove Hermansen. – You do not get such extensive fluctuations as monitoring stations in more populated areas may display, such as Mace Head in Ireland and the Jungfraujoch Observatory in Switzerland.
These two European observatories are located so that they capture air coming in from the Atlantic Ocean. Air masses from this region are often affected by air from highly populated areas in the United States.
If you want to measure the correct background levels, you need really remote observatories like Mauna Loa in the Pacific, Cape Grim in Tasmania and Ragged Point on Barbados. And the Zeppelin observatory, of course – the best background station in the northern hemisphere.
Control and calibration
For NILU to be able to perform high quality air measurements, it is important that those working at, and near the observatory, do not pollute the measurements. Thus, it is crucial to have control of everything in the immediate vicinity, from material selection at the station to where different sources of pollution, such as cars, are situated. The scientists must be absolutely sure that what they measure are real air samples from the Arctic and Antarctica.
To be able to measure accurately, we need our equipment to be in top shape, Hermansen explains.
– The equipment must be calibrated regularly, and correctly.
How and when such calibration takes place depends on the measurement method and type of instrument. Most instruments are tested using a known air sample, a so-called “standard”. In addition, NILU participates in “ring tests”. During these, a gas bottle of air is sent from monitoring station to monitoring station across Europe. Each station measures air from the same bottle, and should get exactly the same result.
– This calibration takes place within large networks, explains Hermansen. – NILU is involved in many different networks, each with its own comparative programmes for instruments and equipment for air sampling. This is not only about measuring accurately, as all measurement stations in a network should measure against the same reference so that the results are comparable.
For particle instruments, there are no similar “standards”. Thus, at a few years’ intervals, representatives from up to twenty of the measurement stations meet at a calibration center in Europe to compare and check that these instruments measure the same.
To ensure that they measure on the same scale as the other monitoring stations around the world, Lunder, Hermansen and senior engineer Are Bäcklund spend a lot of time calibrating the instruments. There are strict procedures to follow.
– Each station also has its own procedures, says Bäcklund, – where we go through a variety of different validation protocols for the instruments. In order to meet the quality requirements we must show that we perform the validation properly and on a regular basis.
In addition to validating the instruments, the NILU crew must have full control over pressure, temperature and airflow through the air inlet the instruments are connected to. All measurements must be checked and logged, data transferred to NILU and disseminated to the different monitoring networks NILU is part of.
Besides all this, NILU occasionally gets visits from representatives of the various networks, for example the Global Atmospheric Watch. They use their
own instruments to perform control measurements on the instruments at Zeppelin.
Once a week, Hermansen goes through all the raw data and checks if they are correct. Only after this control, the measurements will be recorded as approved in the database. He also participates in monthly meetings with scientists from other European monitoring stations, where they go through all data plots, recorded calibrations and deviations. The deviations are carefully investigated to reveal the cause and find solutions.
In addition, there are annual European meetings, where scientists meet and present plots from their measurement stations. If there are any discrepancies, these are pointed out and discussed, and if the deviations are not explained, the data from this particular measurement station may be discarded.
– This is how we ensure that all our data are of good quality, explains Hermansen, – and we learn a lot from each other during these discussions. Especially about instrument problems, which can be anything from a small leak to a worn-out pump or a missing gasket.
All three can tell stories about cases where solving an instrument problem has taken days, weeks, even months – and it is in such contexts these networks demonstrate their worth. It gives the scientists the opportunity to learn from others’ experiences, and find solutions faster than if they had worked alone.
Alle de tre kan fortelle om tilfeller der det har tatt både dager, uker og måneder før de har funnet ut hva feilen er. Og nettopp i den sammenhengen er slike nettverk gode å ha. Der kan de høste av andres erfaringer for å finne løsninger raskere enn om de hadde jobbet alene.
Norge og NILU i polare områder
Alle data NILU produserer ut fra målingene ved observatoriene er åpent tilgjengelig så snart de er kvalitetssikret og overlevert til oppdragsgiver. Data fra både Zeppelin og Trollhaugen blir mye brukt både av norske og internasjonale forskere, kan Lunder fortelle.
– Zeppelin er mye mer tilgjengelig enn Trollhaugen på mange måter, sier Bäcklund. – Det er mye enklere å drifte en del av utstyret vårt der enn på Trollhaugen, av rent logistiske årsaker. Mannskap fra måle- og instrumentavdelingen besøker i snitt Zeppelinobservatoriet annenhver måned. På Trollhaugen derimot, er de en gang i året. Observatoriet er tilgjengelig kun i den sydlige sommersesongen, da fly til Troll kun går i perioden november til februar. Ergo sier det seg selv at det er mer utfordrende å holde alle typer instrumenter i kontinuerlig drift der.
NILU har overvåket luftkvaliteten ved Zeppelin-observatoriet siden 1989 (NILUs aller første luftmålinger på Svalbard ble gjort i Ny-Ålesund i 1974), og i Antarktis siden 2007. Hvordan ble det til at nettopp NILU måler luft fra pol til pol?
– Norge er jo en polarnasjon, og NILU er i en enestående posisjon i forhold til å forvalte ansvaret som ligger i å overvåke lufta og atmosfæren i de polare regionene, sier Ove Hermansen.
– NILU har bygget opp kompetanse og erfaring over tid, og har gjort seg fortjent til renomméet som gir tilgang til de nødvendige nettverkene. Vi har vist at NILU kan levere på kvalitet og kvalitetssikring, og det vil vi fortsette med, avslutter han.
Read NILU annual report 2017:
Read NILU annual report on the web (www.issuu.com):