18/07/2017
Dear Friends,
let's publish some more summaries from the proceedings of the International Symposium of Speleology - Varenna 2017. Research session: Giovanni Badino on underground meteorology.
THE ALMOST INSOLUBLE PROBLEMS
OF ENVIRONMENTAL MEASURES UNDERGROUND
Giovanni Badino
Department of Physics, University of Turin, Italy
La Venta Association
During the past two decades, it has become clear that the underground environment, like the external, is not stable; it shows similar transient variations, Aristotelian “meteora” like clouds, rain, seasonal winds and so on. These variations have two fundamental characteristics:
1. Their amplitudes are much smaller than those outside;
2. Their variability from one cave to another is relatively much greater than in different external environments.
The first point is essentially due to the thermal inertia of underground systems, which behave as low-pass filters, fading the external fluctuations.
The second point is even more important, and poses new challenges. The change of temperature range between locations with continental climate and oceanic rose from 36 °C of Ulan Bator (Dwc-Continental Boreal climate in the Koppen classification), to 8 °C of Ushuaia (ET-Tundra): there is therefore a factor 4.5 between the extremes. The energy deposition behave in a similar way, the Sun power on Earth has an average maximum around 320 kW/m2 in the regions of the Sahara and a minimum of 50 kW/m2 in the North Atlantic, a factor 6 between the two extremes. The variations in the temperature ranges and in the energy depositions inside the caves are vastly larger, at least one thousand factor the first and ten thousand the second. From this point of view, it is impossible to speak of “cave environment”: almost each cave is a different planet…
The progress of the data acquisition has therefore shown that the external meteorological instruments are inherently unsuitable for underground environments measures, and they have be chosen - and often completely rethought -, according to the type of cave. Here are analysed, in particular, the problems associated with the apparently trivial experimental measurements of temperature, humidity and air velocity.
