Heat waves are produced by a mass of hot air coming from another continent. But what causes this unusual atmospheric motion?
If you live in a European city, it is likely that the news of the imminent heat wave that is about to hit the continent has worried you, but perhaps it did not surprise you. In recent years, we have heard constant weather alerts in the media once the summer period has arrived. In Spain, 2015, record temperatures exceeding 40ºC were reached in almost all provinces, and 2017 was the year with the highest number of heat waves in history since 1975.
As forecasters have announced, in the newly released summer of 2019 we will not be free from extreme temperatures either. The Spanish Meteorological Agency (AEMET) issued a statement on Monday 24 in which it states that, with a probability of 80%, in the Peninsula and the Balearic Islands there will be a rise in temperatures caused by the arrival of a tropical air mass continental “very dry, very warm, and with suspended dust” that arrives after an extensive journey through North Africa.
What is a heatwave?
And, most importantly: how do you produce a heat wave?
The physicist and scientific communicator José Miguel Viñas (@divulgameteo) has explained to VERY INTERESTING what are the physical processes that occur in the atmosphere in a heat wave. But, first, we must be clear by what criteria it is evaluated that a rise in temperature is actually a heat wave.
Viñas explains that we must attend to three fundamental principles:
- The first, that the temperature in that place and for the time of year in which we find ourselves are higher than usual, in some cases even reaching records.
- Second, that this average increase in temperature lasts longer than one or two days. In this case, the forecast heat wave begins on Wednesday 26, and will last until July 1.
- Finally, that the extension is not limited to a single area, but is extended to a territory, as in this case, which will affect Western Europe.
The Earth’s atmosphere is dynamic and moving, like the ocean, and these air currents are represented by wave meteorologists. Sometimes these waves, which carry currents of hot or cold air, invade regions outside their usual latitude, altering their temperature. According to Viñas’ explanations, a heat wave occurs as atmospheric ripples become wider and more stationary.
Jacob Petrus ( @jacobpetrus_tve) , geographer, climatologist and science communicator who presents the program Here on Earth , explains in a conversation with VERY INTERESTING how science defines a heat wave: “A heat wave is an episode of high temperatures that has of being generalized, and whose temperatures are ‘significantly high’, from the measurement of the data by percentiles “.
That is, taking all the maximum temperatures, the heat wave is defined by 10% of the highest temperatures ever recorded.
The role of climate change in heat waves
Despite the fact that heat waves are a phenomenon that occurs naturally, scientists observe that their frequency and intensity is not so. In the first and second decades of the 21st century, heat waves have been more intense and frequent than those observed in the 70s, 80s and 90s. And it is not unreasonable to think that the human factor in the global increase in temperatures could play a role in this phenomenon.
For José Miguel Viñas: “These changes in atmospheric dynamics could be a response to the increase in temperature, as well as some unusual characteristics observed in the melting of the Arctic.”
Along the same lines, Petrus acknowledges that extreme events increase in the context of climate change: “We knew that, as a result of climate change, extreme events were going to be enhanced, such as heat waves or cold waves. The reason is that, when there is an easier exchange between cold air masses between hot and cold air masses, it is easier for what we get to be heat waves ”.
And he adds: “There is no room for doubt; the masses of hot air coming from Africa are more and more frequent, causing longer and more intense summers ”.
Are we being alarmists?
José Miguel Viñas is not in favor of being a catastrophist, but considers that it is important to warn the population so that they take protective measures against episodes of unusually high temperatures : “One of the consequences is drought cycles, and that there are more and more problems living in a certain area and access to water; in this sense, there is a human component, and that is that they are more or less prepared to fight against it ”.
For its part, Petrus highlights people over 65 as a particularly vulnerable population : “They are those who cannot easily move to cooler areas, or even take a bath, or who do not have air conditioning.” Both experts recognize an increase in mortality related directly or indirectly to heat waves.
On the other hand, Jacob Petrus does not forget that there are other environmental problems that we must worry about more urgently: “Some examples are pollution episodes in large cities, which have a direct impact on health, or pollution from plastic ”.
