The polar environment is under a constantly increasing interest: climate change comes first and comes faster in the arctic. Multitudes of observations are needed to understand the environment and its evolution. The traceability of data becomes fundamental for the comparability of the many and different measurements’ results.

The Ny-Ålesund international research base offers a unique infrastructure for environmental research and an opportunity to establish a fruitful cooperation with the metrology community.

Bringing metrology to the Arctic. This has been the scope of the Arctic metrology campaign organised within the frame of the MeteoMet project. A special portable chamber, purpose made to calibrate atmospheric sensors in extreme ranges, was shipped from INRiM to Ny-Ålesund, Svalbard in May 2014. One month later, Italian metrology staff reached the Arctic base and performed the special calibration procedure for the GRUAN site operated by AWI-PEV.

The Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) is an international reference observing network, designed to meet climate requirements and to fill a major void in the current global observing system. GRUAN observations provide long-term, high-quality climate records from the surface, through the troposphere and into the stratosphere. To better fulfil the principle of traceability, uncertainty evaluation and calibration documented procedures, the GRUAN working group (WG) established a collaboration with the metrology community. Metrologists now sit in the GRUAN WG and formal collaboration has been signed. The Arctic Metrology campaign was not only a deliverable for the EMRP Project MeteoMet, but also part of this formal collaboration between climate science and metrology.

The first GRUAN certified station has been the AWI-PEV research base in Ny-Ålesund, Svalbard. Here, the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, launches a Vaisala RS92 radiosonde every day at noon. Prior to the launch, each radiosonde runs through additional ground check measurements to optimise the characterisation of the sonde’s performance. Beside the laboratory check, an in-field pre-launch check is performed immediately before hanging the radiosonde to the balloon and leaving it flying.

This check involves a reference thermometer and a barometer, to compare the reading of the radiosondes and link them to one traceable value. Pre-launch ground temperature and pressure, moreover, are important metadata for the radiosonde daily records. The two sensors are hosted in a weather hut, a Stevensons Screen, where the radiosonde is left for about one hour before launch. Those sensors were the subjects of the calibration performed by means of the special chamber.

This new chamber coded EDIE 1 (Earth Dynamics Investigation Experiment 1) was designed and manufactured at the Italian Institute of Metrology (INRiM) in the framework of the MeteoMet project to ensure data traceability and to obtain more comprehensive data on the performance of pressure and temperature sensors. The device allows simultaneous and independent control of pressure and temperature across the whole range of ground atmospheric variability as well as for the Arctic range that meets at the Ny-Ålesund station.

It is made to calibrate temperature and pressure sensors, also evaluating the mutual influences between those two quantities. This last point was of special interest for the Arctic application, since it is of utmost importance to take into account the effect of the temperature on the readings of the barometers, especially when exposed to such polar conditions. The chamber is equipped with reference sensors directly traceable to national standards. This is to shorten the traceability chain and to guarantee well-documented calibration uncertainty.

INRiM staff prepared the calibration chamber and packaged all the required equipment into a box weighing less than 200 kg. This was shipped from INRiM on 20th May and arrived in Ny-Ålesund by boat preceding the arrival of the INRiM staff in the middle of June.

The stay planned for the INRiM staff was only three days for two researchers and seven days for a third member of the team. Two rounds of calibration were scheduled in addition to a short training session for AWI staff on the use of the calibration chamber, procedures, calibration curves and uncertainties. For this reason all assembling and start-up process of the device were previously studied in detail to keep operational times to a minimum.

The chamber was left in Ny Ålesund for a further month, to be used in the test and calibration of other instruments. It was also used to calibrate some of the thermometers and barometers of the climate change tower, the innovative structure that hosts chains of instruments from ground level up to 30 metres. The whole system was then re-crated and sent back to INRiM.

The work involved a strict collaboration with the AWI-PEV and INRiM staff, all working closely while at the Ny Ålesund base. The GRUAN research at the AWI observatory now benefits from more robust data and a metrological approach to measurement recording.

This positive result opened the possibility of extending the application of a robust metrological approach to the many other interdisciplinary research activities carried out in the numerous research stations in the Svalbard. The plan for a permanent calibration laboratory was then drafted and is now being discussed within the metrology communities and the scientists operating the Arctic research bases.

The three main answers that metrology can give to polar environmental research are:

1.  Calibration of sensors in an extreme range, where ‘normal’ procedures usually lose quality and tail values sometimes are not even included.

2.  Reduced traceability steps, to allow more accurate measurements in an area where climate trends are amplified, and more accurate measurements means reduced time to capture trends.

3.  Overcoming logistical problems in shipping sensors to in-land calibration laboratories, and allows the opportunity for the operator of the instruments and researchers to directly follow the calibration and test of their devices.

This first Arctic Metrology campaign was performed during the stay in Ny Ålesund of the Italian Ambassador in Norway and in the presence of the Italian Foreign Affairs Ministry Secretary. The work was then presented at the Arctic circle Assembly 2 , an event opened by Angela Merkel, German Chancellor of the Federal Republic of Germany, hosting ministries from most of the Arctic Council countries. Such activities showed how Euramet can bring metrology to remote areas, address data quality and traceability needs, and improve the quality of such high level scientific research in a key area of our planet.

Published: 16th Sep 2015 in AWE International