In the Iberian Peninsula, in recent years and on a recurring basis, we hear about meteorological records, that this or that place, town or province has broken a record for the highest temperature. It may be strange, therefore, the news about records of extreme minimum temperatures that these days are appearing in the media.
First of all, it should be noted that these minimum records should not be related to climate change. The study and monitoring of climate change, natural or anthropogenic, is based on the analysis of long data series and not on specific records or record values.
In addition, it is necessary to know the characteristics of the places where these temperatures have been recorded to understand why it is not so strange that these records occur in our latitudes.
Minimum temperatures, not always at altitude
On the surface, these records would be expected to occur at the highest peaks of mountain systems, as temperatures typically drop as altitude is gained. But the exception to this general rule occurs when the meteorological phenomenon known as thermal inversion appears .
Thermal inversions occur with stable weather, light winds and the absence of solar radiation. Under these conditions, the cold, denser air is deposited on the surface, so it will be in the depressed or sunken areas where the lowest temperatures are recorded.
The phenomenon can be observed frequently in our latitudes during the winter months, when it is not strange to obtain lower minimum temperatures in the plateaus than in the tops of the mountain systems.
Cold air pools
When these depressions in the terrain are closed and are located in environments where there are strong thermal inversions, the cold air descends towards the bottom of the depression and can form a pool of cold air or CAP ( cold-air pool in the English bibliography). The temperatures that are reached inside these depressions can be much lower than those of the adjacent or surrounding areas.
In our geography, these depressions (sinkholes, poljés) are usually associated with calcareous areas, where karst processes dissolve the limestone through erosive phenomena related to water and snow.
Externally, one of the main manifestations of karst modeling is geological depressions. These depressions are abundant in the limestone mountain systems of the Iberian Peninsula, highlighting the massif of the Picos de Europa, in the Cantabrian mountain range.
One of the most relevant depressions in Picos de Europa is the Vega de Liordes, located in the Massif Central, in the province of León.
Weather stations in key locations
The thermal behavior of these places has gone unnoticed for many years in the Iberian Peninsula. The pioneers in monitoring these sites in Spain have been, precisely, people who are fond of meteorology. Through associations or private projects, they have financed and installed reliable and calibrated meteorological instrumentation that allows, for very few years, to have data from these very peculiar spaces.
One of the best examples is the meteorological station that the ACAMET meteorological association installed in Vega de Liordes in 2019, at an altitude of 1,820 m.
Until that date, the absolute minimum temperature recorded by a meteorological station in Spain was -32.0 ° C at Lake Estany Gento (Lleida), on February 3, 1956. Currently, this record has been widely exceeded: in the At dawn on January 7, 2021, the Vega de Liordes station registered -35.8 ° C.
The day before, January 6, 2021, also at dawn, a temperature of -34.1 ° C was also reached in Clot del Tuc de la Llança, a place with similar geological characteristics located in the Lleida Pyrenees.
The dawn of January 7, 2021 was especially cold in the Cantabrian Mountains. This is reflected in the records obtained by the network of stations of the NOROMET association, highlighting the almost -30 ° C at a point in the Leonese region of Babia, at only 1,200 meters of altitude.
Data of great scientific value
For skeptics who doubt the validity of these data, it must be emphasized that these facilities meet all the requirements set by the WMO (World Meteorological Organization) and are regularly maintained and calibrated.
The Vega de Liordes station has several temperature sensors that, when weather conditions permit, can be collected to validate their records.
At present, as has been seen in this winter episode, various associations and meteorology fans are contributing, altruistically, to the study, monitoring and enhancement of all kinds of places located within the Spanish geography that present singularities notable meteorological or climatic conditions. These data have great scientific value and contribute to the improvement of meteorological observation.
Andrés Merino, Researcher in Meteorology and Climatology, University of León
This article was originally published on The Conversation. Read the original.
