Robust outdoor data loggers monitor air temperatures in geological depressions to pinpoint areas of extreme cold.
Researcher Stephan Vogt is using Tinytag data loggers to
identify the coldest places in Switzerland, which contrary to
popular opinion are not recorded on the highest mountains! Stephan,
who has an Earth Sciences Master's Degree from the Swiss Federal
Institute of Technology, works for the National Weather Service. In
his spare time he is working on this private project, attempting to
locate the coldest areas which are to be found in closed geological
depressions called sinkholes or dolines, where cold air can become
Sinkholes with gentle surrounding slopes, fresh snow cover, air
masses of arctic or polar origin, a clear sky and no wind are
needed for the perfect situation: under these conditions
temperature can drop 20 to 30°C within a few hours during the
night. In these cases temperatures in a sinkhole can be 20°C to
35°C (under extreme conditions) lower than at the same altitude in
the free atmosphere: a so-called inversion is formed.
The coldest measured temperature at an official station in
Switzerland is -41.8 °C in La Brévine (a village in the Jura
Mountains close to the French border, (elevation 1040m); an
unofficial measurement of -52.5 °C exists from Glattalp (1860m) in
central Switzerland but Stephan believes this is not the end of the
story! He aims to use Tinytags to continuously monitor in sinkholes
which have been identified as the most promising for experiencing
extreme cold temperatures. In each doline, a monitoring station is
placed as close to the lowest point as possible (where the lowest
temperature occurs) and an additional station is situated at the
upper rim in order to determine the strength of the inversion
(deviation to the conditions outside of the doline).
Since April and November 2016 respectively, two first sinkholes
have been equipped with monitoring stations which incorporate
data loggers with an accompanying PT100 probe, housed in an
actively ventilated radiation shield. The stations are set up to
closely meet the requirements of the World Meteorological
Organisation. One is the depression of Lake Sämtis (1209m) and one
the sinkhole of Alp Hintergräppelen (1286m) in the Alpstein
Mountains in north eastern Switzerland.
Readings are taken every ten minutes, and the data downloaded
every 75 days. The stations at the upper rim of each doline are
equipped with Tinytag TK-4023 data
loggers set to record every 20 minutes, and housed in a passive
ventilated radiation shield. These stations in the two dolines are
prototypes in order to gain experience, the really interesting
candidates are yet to come!
Specifically, the recorded information will help to identify the
coldest temperatures and highest temperatures. This allows Stephan
to derive what amplitude can occur within one day and how fast
temperature can fall or rise. In addition, it will identify how
many ice days and frost days occur.
Results of the monitoring are recorded in a database for
analysis and presented online at https://kaltluftseen.ch The results are shared
with cold air pool enthusiasts from all over Europe including
Stephan comments, "I was looking for a temperature recording
solution which works under extreme conditions: temperatures of
under -40 °C can occur and an IP68 rating is needed in the dolines
since flooding is possible. Tinytag data loggers provide a good
combination of accuracy, functional efficiency, ruggedness at low
temperatures and cost. I'm looking forward to reaching the limits
of the Tinytags' specifications!"
The image shows a close-up of the Hintergräppelen monitoring
station (rights reserved).
The file shows an example of a standard monthly summary
graph for each cold air pool: it shows the values for
Hintergräppelen frost hollow for January 2017 where an astonishing
-38.2 °C was recorded in the night from January 6th to January 7th