The climate changes, the words too. While the whole of France will be confronted with extreme temperatures, between 35 and 40 ° C, from Wednesday June 15, the climatologist Christophe Cassou evoked the term “feather” to describe this heat wave exceptionally early.
It is acquired! will undergo this week #Heat wave #HeatFeather.
Only uncertainties: intensity (between exceptional & record) & duration (linked to its ± geographical ext. towards North).
One to describe its particular dynamic, the link with #Climate changeetc.
pic.twitter.com/7RMpcHZ8FN— Christophe Cassou (@cassouman40) June 12, 2022
This image, used by one of the main authors of the sixth report of the Giec, actually comes from the English expression “heat plume”, which can be translated into French as “panache” or “plume de heat”. Far from being trivial, this new name makes it possible to qualify a phenomenon directly linked to human activity and climate change, as Christophe Cassou explains to franceinfo.
Franceinfo: What is a “feather” of heat?
Christophe Cassou: There are several atmospheric dynamics to generate heat waves over a region and in particular over Europe. For example, there’s the heat dome, which was made popular last year during the heat wave in Canada, and the heat plume – or heat plume. These terms make it possible to approach in a more precise way the physical processes which are at the origin of these phenomena, even if one does not use them within the scientific community.
The heat plume is a tongue of heat that detaches from the Sahara, the Maghreb or the Mediterranean, which rises towards the North, sucked in by a small “cold drop” [une masse d’air froid qui se déplace à plus de 5 000 m d’altitude, avec des températures allant de -20 à -10 °C] which is located off France (on the Atlantic coast) or Spain, which plays the role of a gear which will transport the hot and dry air which comes from the south to the north. This warm air generates a heat wave (or heat episode) where it develops.
But where does this term come from?
The expression “heat plume” is a translation of the English expression “heat plume”, which can also be translated as “heat plume”.
“I kept the word ‘feather’ because I find it more poetic and because it is important to use images to communicate physical processes to the general public.”
Christophe Cassou, climatologistat franceinfo
How is it different from a heat dome?
Unlike a heat dome, the feather is an atmospheric dynamic that is said to be advective. That is, it is a transport dynamic, taking air from the south bringing it north, whereas the heat dome is a blocking dynamic. In this case, an air mass locks in a region. In summer, it gets hotter and hotter, it feeds itself, the winds circulate around this dome without penetrating inside.
“With a heat dome, a heat wave sets in locally and statically, the opposite of the feather, which is a transport dynamic.”
Christophe Cassou, climatologistat franceinfo
Does this mean that a feather of heat is not intended to last?
Generally, the heat plumes are shorter, insofar as they correspond to very marked and very active atmospheric dynamics. The challenge is to understand how the small cold drop, which acts as a gear, will evolve and then sweep away this feather of heat that has been put in place.
Since it is more static, the heat dome is usually longer, that’s why this situation is called atmospheric “a blocking situation”because this dome is created day after day (it can last one or even two weeks during extreme events).
The whole challenge is to know how this feather of heat will evolve and condition the end of a heat wave episode.
“Today there is deep uncertainty about how this heat wave will end or last. Will it spill over into the weekend or end on Saturday or Sunday?”
Christophe Cassou, climatologistat franceinfo
How do these heat plumes have a link with climate change?
Our studies show that it is indisputable that human activities are the cause of climate change and that they make extreme climatic phenomena (we speak of heat waves, torrential rains, drought) more common. Today, they are more frequent and more severe, in the sense that they last longer, are more intense, and their seasonality is modified: heat waves appear earlier and later [dans l’année].
“The summer season has stretched out over time. It’s a signature of climate change.”
Christophe Cassou, climatologistat franceinfo