The Alpine environment has been under constant observation for many decades by climatologists. Glaciers in middle latitudes’ mountain ranges (Himalaya, Rocky Mountains, Cascades, Andes and of course Alps) are retreating fast since at least the middle 19th century, when a systematic effort of classification and characterisation of glaciers has started in the Western world; moreover, the glacier mass loss in the Alps has been shown to have accelerated during the last few decades.
Glaciers retreat is among the principal and foremost tracers of climate change, a challenge we are all called to face in the years to come.
It is therefore of paramount importance to measure air, soil, water, ice and permafrost temperatures in these regions with the maximum accuracy possible, performing accurate calibrations with dedicated instruments and procedures in order to full evaluate the uncertainties.
In the framework of the European project MeteoMet1, INRiM (the Italian Institute for Metrologic Research) and the whole metrology community have started a series of actions dedicated to the improvement of temperature and temperature-related measurements in the Alpine regions, as a service to meteo- and climate operators and research institutions in the field of environmental protection.
Calibrating thermometer chains
One of the first actions was the calibration of a series of different thermometer chains used by two Italian regional environmental protection agencies (ARPA Piemonte and ARPA Valle d’Aosta) to monitor the temperature of permafrost at different depths and in different high-mountain sites in the Alps.
This initiative is one of the first steps towards understanding the issues coming from different techniques adopted by different agencies to pursue the measurements of permafrost temperatures.
These calibrations have been performed at INRiM between July and October 2016, in the Environmental Thermometry lab, using a primary standard thermometer – calibrated against national reference fixed points – and high quality bridges for the readouts.
Laboratory versus in-situ calibration
Calibrating in laboratory has its undeniable advantages: heavy tools and facilities are easily available, as well as electric power; moreover, work is not restricted in periods of good weather and can be carried on in less time and more safety. The downside is that the instruments are required to be removed from the site for a more or less extended period, to be transported in laboratory and then back to the site, risking mechanical shocks during the trip that can change their characteristics and render the calibration useless. Moreover, calibrations performed in such different environmental conditions are known to be insufficient for a thorough assessment of the related uncertainties.
For these reasons, an in-situ calibration campaign has been scheduled for summer 2017, in cooperation with ARPA Piemonte, on their already-operating permafrost thermometer chains at the Colle del Sommeiller, a 3000m high mountain pass on the Italian western Alps (Figure 1). The site hosts three different bores, ranging from 5 m to 100 m in depth, where a total of 36 thermistors are deployed. In close vicinity of the bores, an Automatic Weather Station (AWS) is placed, in order to link the temperatures measured inside the permafrost bores to the atmospheric conditions on the surface.
The calibration campaign will be carried on with the help of portable liquid thermostatic baths and readout bridges, using a secondary “travelling” standard thermometer (already calibrated in laboratory against a primary standard) as a reference for temperature, and a diesel generator to supply power. This campaign will help achieve a higher measurement quality of this phenomenon, crucial to understanding the temperature dynamics in the Alps.
Snow’s effect on temperature measurements
A second research branch is dedicated to the evaluation of snow coverage effect on air temperature measurements performed by AWS. It is known in the meteorological community that the sheer change in surface reflectivity (albedo) caused by snow can affect the temperature measurements in quite a dramatic way, thereby rendering AWSs in Alpine sites, particularly affected by this phenomenon, less reliable.
Within the MeteoMet project, a dedicated experiment has been planned to address this issue. Temperature sensors and shields, along with albedometers, hygrometers and anemometers have been collected from different manufacturers and characterised in the Climate Data Quality Lab (CDQL), jointly run by INRiM and the Italian Hydro-geological Protection Research Institute (CNR-IRPI), during the summer of 2016 (Figure 2).
The instruments have been transported to the experimental site (previously identified in April), an ARPA Piemonte-operated station in the mountain village of Balme, north of Turin, and mounted in September-October, at an elevation of approximately 1500m above sea level (Figure 3).
The experiment consists in two stations, equipped with identical temperature sensors, at a distance of approximately 20m: halfway between them, a station hosting shared dataloggers and some ancillary instruments has been placed. One measurement station is constantly kept free of snow, while the other is left in its natural conditions. By comparing the data recorded by the different couples of instruments, and taking into account ancillary measurements, it is possible to evaluate the different behaviour of several types of commonly used sensors under different conditions of snow coverage.
A measurement protocol, complete with a theoretical model of the different influences expected by different conditions on the temperature measurements, has been drafted prior to the mise en place of all the equipment. This will help focussing the data analysis on certain, more “promising” periods of time, where the combined effect of the quantities of influence is expected to boost the phenomenon.
The experiment is now up and it will run for the entire winter season.
The RiST project
The cooperation with CNR-IRPI on the Alpine environment continues also in another project involving the same mountain community of Balme: it is the RiST project (Ricerca Scientifica e Tecnologica nel bacino glaciale della Bessanese), whose aim is to study relations between climate conditions and morpho-dynamical processes in a glacier area, with emphasis on the role of temperature. For this purpose, a series of 10 small-sized “MicroTemp” temperature sensors – designed to be waterproof and extremely responsive – have been calibrated at INRiM laboratories, then transported in July 2016 to the Bessanese glacier basin at 2700 m, where they have been placed in different interesting geological formations (glacier fusion stream, rock, scree) in order to monitor constantly their temperatures. After one month of in-situ testing, the instruments were removed from the site and their behaviour evaluated. A subsequent trip to the glacier basin (August 2016) was performed to put back the sensors in their designated sites, in order to let them acquire data for the whole winter season (Figure 4).
During these missions, a high-resolution livecam3 was also installed with both scientific (monitoring the basin for rockslides) and touristic purposes. A further mission is planned (summer 2017) to equip the livecam with an INRiM-calibrated AWS, again serving a double purpose: pair the temperatures measured by the “MicroTemp” sensors with air temperature, and provide real-time weather information superimposed on the livecam feed.
In December 2016 a cooperation with the Earth Science Department of the University of Turin also started. A calibration campaign of 20 miniaturised “iButton” temperature sensors, used by the Department to monitor permafrost temperature in a periglacial area in Aosta Valley (Northwestern Alps), was carried out. This action was part of a MeteoMet project task, aimed at the assessment of the response of various temperature sensor models to mechanical shocks – a common problem when employing delicate equipment in uncomfortable places, i.e. a drop from elevated ground, blows, etc. These thermometers are planned to be calibrated both in air – using a climatic chamber at INRiM (Figure 5) – and in liquid – with a thermostatic bath at the CDQL. The sensors will undergo a standardised mechanical shock and their calibration will then be re-evaluated, in order to estimate the degree of change in the calibration curve. This will help evaluate more thoroughly the uncertainties correlated to such measurements in difficult conditions.
All these actions are part of the same vision that aims at bringing the metrological approach at measuring environmental temperatures in the areas where it is needed most: the Arctic (see AWE International Issue 43, September 2015) and the high mountain environments.
On this sensitive subject, INRiM and the MeteoMet consortium are promoting a round table event, to be held in Moncalieri (Italy) on 15 February 2017, to discuss ideas, challenges and future endeavours among Italian and European key operators in the field of environmental protection, geophysical and atmospheric research, high mountain observation and instrument manufacturing. This will facilitate a cross bridging discussion towards improving data quality in atmospheric and permafrost measurements in alpine environments, evaluating components of site measurement uncertainty, reference grade installation characteristics for high mountains cryosphere observation, with a clear metrological point of view.
The need for quality data and traceable measurements, which are key in understanding how climate change is affecting and is going to affect Earth in the near future, is the fundamental aspect that brings our work in such remote yet important areas of our planet.