Heat waves are likely to intensify in France and become more frequent in the future. And the terms to qualify them are also diversifying: what are the differences between a heat wave and a heat wave? What is meant by feather or heat dome?
An episode of strong, early heat awaits France from this Wednesday, June 15, 2022. The phenomenon is expected to last until the weekend. ” In France, the highs should reach or exceed 35 to 38 degrees Celsius in the middle of the week and the lows will not drop below 20 degrees Celsius. “, announces the establishment of meteorological forecast.
The phenomenon is referred to as heat wave » by Météo France, but we can also speak of « heat feather », to describe this episode occurring in France this week. What is the difference with a heat dome? And with a heat wave?
When do we speak of a heat wave?
The term heat wave is used when abnormally high temperatures are observed for several days in a row. ” A heat wave combines intensity and duration of the phenomenon. At Météo France, they are listed from the national thermal indicator, when a high enough temperature peak is reached, and the temperatures remain high enough for at least 3 days. », abstract on Twitter Gaétan Heymes, forecasting engineer at Météo France.
We speak of a heat wave when the temperatures:
- Exceed the threshold of 25.3°C at least once (average temperature in France for a given day),
- Remain above 23.4°C for at least 3 days,
- Do not drop below 22.4°C.
Regarding the heat episode expected this week, it ” would meet these criteria on the days of Thursday, Friday and Saturday “, specifies Météo France.
However, it should be noted that the definition of heat wave is not universal. It not only depends on countries and climates, notedGaétan Heymes, but in addition the notion of “heat wave” is sometimes used in an equivalent way to that of “heat wave”: “ In many languages, the notion of ‘heat wave’ is literally translated as ‘heat wave’: ‘heatwave’, ‘hitzewelle’, ‘ola de calor’… », pointed out the expert.
When do we speak of a heat wave?
The word heatwave is assigned to situations concerned by an orange or red heat wave vigilance “, explained Matthieu Sorel, climatologist at Météo-France, during a point to the press on June 14, 2022. A heat wave is manifested by a “ episode of high temperatures, day or night, over a prolonged period “, can we also read on the site of Météo France. The exceptional dimension of nighttime temperatures is taken into account. When temperatures are high for several days in a row, the heat can pose a health hazard.
Heat waves tend to occur between early July and mid-August, but France experiences increasingly early and intense heat waves. This was the case from June 17 to 24, 2017, with 90 departments placed on yellow or orange heatwave vigilance. The trend is for an increase in the frequency and intensity of such heat events in the future. ” The frequency of events is expected to double by 2050 “, warned Météo France.
What is a heat dome?
The term “heat dome” is used to describe a rather static phenomenon. ” We are under the influence of an anticyclone [ndlr : une région de l’atmosphère caractérisée par de hautes pressions]. Hot air is trapped under this virtual jar, where the heat wave builds day after day “, describeMatthew Sorel. The rise in temperature is then gradual, over the days.
What is a Heat Feather?
The expression “heat feather” appeared in June 2022, explained by climatologist Christophe Cassou, research director at the CNRS and main author of the 6th IPCC report. It means ” a plume, a tentacle that comes from the south », does he sum up on Twitter.
” We are in an advection configuration [ndlr : déplacement horizontal] warm air from the south. It’s an advective heat wave », completeMatthew Sorel. The phenomenon is more dynamic than that of a heat dome, the air particles taking the same path, as in a funnel.