Context: Recently, a study revealed that an extremely large ‘Azores High’ (a subtropical weather phenomenon) has resulted in abnormally dry conditions across the western Mediterranean, including the Iberian Peninsula, primarily occupied by Spain and Portugal.

Azores High

• Azores High is a subtropical high-pressure system that extends over the eastern subtropical North Atlantic and Western Europe during winter.

• It is associated with anticyclonic winds in the subtropical North Atlantic.

• It is formed by dry air aloft descending the subtropics and coincides with the downward branch of the Hadley Circulation.

What is Hadley Cell?

• Hadley Cells are the low-latitude overturning circulations that have air rising at the equator and air sinking at roughly 30° latitude. 

• They are responsible for the trade winds in the Tropics and control low-latitude weather patterns.

Key finding of study

• The study identified a robust increase in the frequency of extremely large Azores High Area(AHA) events and an overall expansion signal in the winter Azores High over the past 100 years.

• This expansion is driven by external climate forces and the only external forcing that produces this signal in the industrial era is atmospheric greenhouse gas concentrations.

Impact of the extremely large ‘Azores High’

• Extremely large ‘Azores High’ results in abnormally dry conditions across the western Mediterranean including the Iberian Peninsula primarily occupied by Spain and Portugal.

• For instance, an annual drying of 5-10 millimetres per year per decade has been recorded in the Iberian Peninsula throughout the second half of the 20th century.

• These projected changes make agriculture in the Iberian region some of the most vulnerable in Europe.