The subtropical high-pressure systems play a fundamental role in influencing global weather patterns, particularly visible during the summer season.
The study by researchers from Tehran delved into these phenomena, focusing on the systems of the Azores and Hawaii, two key figures in the meteorology of the northern hemisphere.
The analysis aims to understand the dynamics of these anticyclones through the use of atmospheric data, with particular attention to characteristics such as sea level pressure, divergence, and geopotential height.
The investigation clearly distinguishes between the high pressure of the Azores and that of Hawaii, taking into account not only pressure values but also the rotational dynamics present in the upper levels of the atmosphere.
The data used, covering a forty-year period from 1979 to 2018, were extracted from the European Centre for Medium-Range Weather Forecasts (ECMWF) and its ERA5 version.
This extensive set of information allowed for the examination of how these systems evolve and move on a temporal and geographical scale, with particular attention to the regions of the North Atlantic and the North Pacific.
One of the most relevant findings from the study concerns the behavior of sea level pressure and geopotential height during the month of July.
During this period, the maximum pressure does not necessarily coincide with the maximum subsidence of the air, thus challenging the theory that subsidence is the dominant factor in the formation of high-pressure areas.
On the contrary, the study highlights the importance of the ascent of warm air and the release of latent heat on the western flank of the anticyclones, key elements in the formation of high-pressure ridges.
This contrasts with traditional theories, such as the Hadley cell, which proposed a more simplified explanation of the phenomenon.
The research has shown that the zonal mean of the Hadley cell is significantly weaker during the summer of the northern hemisphere compared to that of the southern hemisphere, highlighting an insufficient circulation to explain the high-pressure peaks occurring in the northern subtropical zones.
The intensification of the high pressure of the Azores, in particular, has significant impacts on meteorology in Europe.
During winter, this high pressure reduces the incidence of severe weather, decreasing the chances of cold waves and extreme snowfall.
However, in summer, the high pressure of the Azores acts as a sort of shield, preventing the arrival of disturbances, which contributes to prolonging and intensifying heatwaves.
These are becoming increasingly common and are a determining factor in the rise of terrestrial temperatures, with implications for human health and the environment.
High pressures, especially in South Asia and Southeast Asia, exacerbate the impact of pre-monsoon heatwaves, which can have devastating consequences, increasing the number of casualties.
In these regions, the rise in temperatures combines with a change in the monsoon rain regime, leading to climatic variations that can cause severe food crises.
These phenomena highlight how climate change, also influenced by the dynamics of high-pressure systems, represents a direct threat to food security and social stability.
Even in Northern Italy, the repercussions of high pressures are evident.
The increasingly hot summers reduce the possibility of snow in mountainous regions, limiting the ski season and putting the winter tourism economy at risk.
In winter, high pressures can block Atlantic disturbances, reducing snowfall even at higher altitudes.
This scenario is set to become increasingly common, with direct effects on water resource availability and agricultural management, particularly relevant for areas already exposed to extreme climate changes.
The research from Tehran fits into a broader debate that questions traditional interpretations of climatic and meteorological models.
The idea that Hadley cells are similar in both hemispheres is contradicted by observations showing how the landmasses of the northern hemisphere warm much more rapidly than the oceans of the southern hemisphere.
This warming accelerates the formation of more intense tropical high pressures in the north, contributing to the increase in heatwaves.
The intensification of high pressures in the northern hemisphere also has a direct impact on the course of the seasons.
Milder winters and hotter summers increase the frequency of extreme weather events, such as droughts and floods, profoundly affecting densely populated areas, especially in Europe and Asia.
If confirmed, this trend could have significant consequences for the future of the global climate, making it increasingly difficult to predict events such as snowfalls or seasonal rains, with devastating consequences for agriculture and water resources.
The in-depth study of subtropical anticyclones, such as those of the Azores and Hawaii, provides valuable insights for better understanding large-scale weather patterns and their evolution in the context of climate change.
The study highlights that a global and integrated view of these phenomena is crucial for developing mitigation and adaptation strategies that can effectively address the challenges posed by extreme climatic events and the rise in temperatures.
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