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Anticyclone of the Azores, a phenomenon that we often hear about, especially when the warm season approaches, but which is not always so clear in our mind. This is one of those names that sound familiar to everyone but that few know specifically anticyclone of the Azores it therefore remains almost a mythical, fictional "creature" that comes to mix the climate of our summer days and to make us draw fans and fans. It is not an invented "monster" but one specific atmospheric phenomenon with precise characteristics and frequencies.
Anticyclone of the Azores
The anticyclone of the Azores it's not just about these islets, otherwise it wouldn't be so well known to us and to many other countries. We can generally say that it presents itself in the areas of the North Atlantic Ocean and has its maximum atmospheric pressure on average near the homonymous islands.
In Italy, when the anticyclone of the Azores comes to influence the climate, what happens is that the air masses subject to compression are of Atlantic origin, therefore fresher, and it follows that the effects of subsidence overheating on ground temperatures become much milder.
Azores anticyclone: what it is
Having ascertained that it is not an imaginary creature with strange features, we can describe the Azores anticyclone as simply a semi-permanent high pressure area of subtropical oceanic origin.
This high pressure area is produced by the same atmospheric circulation, in correspondence with the affected latitudes. It creates its own a band of semi-permanent high pressures on both hemispheres and is a consequence of the atmospheric subsidence of the Intertropical Hadley cell.
When in Italy some heat waves, those that the news so much love to put in the headlines as "emergencies", is not always about anticyclone of the Azoresindeed, it is usually the African anticyclone that is the origin of these high temperature events. This area of high pressure, "African", usually positioned above the Sahara desert, only a altitudes above 1000-2000m.
When you want to announce the arrival of a heat wave more intense than average, in the summer, in Italy, you can often hear the expression "anticyclone coming". May it be that of the Azores or the African one, it is always hot even if there are differences between the two phenomena.
L'anticyclone of the Azores affects not only the climate that reigns in the summer on our peninsula but also the weather situation in the rest of Europe because it can cover a large area, the one that extends from the Mediterranean to almost Arctic Circle.
The anticyclone of the Azores belongs to the group of subtropical anticyclones, in the winter months, as it is positioned, it allows a large number of disturbances to access the Mediterranean, in the summer months it guarantees good weather and high temperatures because, expanding, protects the Mediterranean from perturbations.
Anticyclone in Italy
When an anticyclone, which is of the Azores or African, stretches towards Italy, let's expect heat waves. It is almost automatic and not for an urban legend or an idiom. What happens is clear even if not trivial to explain.
The clear sky favors a strong insolation on the ground, in a condition of prevalence of descending currents, which approach a "warm" ground it generates itself of the additional heat due to subsiding motions. That's why it's hotter than ever when the anticyclone arrives.
The heat and steam given off from the ground they are unable to dilute upwards due to the slow and descending currents, and thus remain to create a thin layer of a few hundred meters close to the ground. Day by day heat and humidity accumulate and the heat is increasingly unbearable because it is also “sticky”.
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