Oceanic circulation would be the main engine of the asymmetry in the regimes of tropical rains. Although it rains more in the northern hemisphere than south of the equator, the southern hemisphere is more exposed to solar radiation, which causes a higher rate of increase in the moisture.
This observation has always been a mystery, but today an American research team concluded that this phenomenon could be attributed to the oceanic meridian circulation.
Below the tropics, it rains more in the north than in the south. Precipitation near the equator is regulated by the zone of intertropical convergence (ITCZ), an atmospheric band of several hundred kilometers formed by the convergence of masses of warm air and humid, driven by the trade winds.
What is the Intertropical Convergence Zone?
La ZCIT It is a region of low pressure caused by the convergence of the northeast and southeast trade winds. These warm, moist air masses rise when they meet, forming clouds and precipitation. This area is characterized by constant rain and intense storms in the tropics.
This cloud belt is the ascending branch of the Hadley cells, which distribute the excess energy from the equator to higher latitudes. However, the ITCZ ​​is not located exactly at the equator, but at approximately 5°N, which causes a asymmetry in rainfall patterns between both hemispheres.
Scientists initially believed that this asymmetry was caused by the geometry of the oceans, attributing it to the distribution of continental masses and ocean temperature. However, recent research has shown that the thermohaline circulation is the main responsible for this phenomenon.
Impact of Climate Change on Rainfall Regimes
Another key factor that has altered rainfall regimes in the northern hemisphere is the climate changeRecent research has shown that the rising global temperatures is transforming rainfall cycles in several regions.
In particular, the mountainous regions of the Northern Hemisphere are experiencing a noticeable change: the snow is turning into rainAccording to studies by the Lawrence Berkeley National Laboratory, each additional degree Celsius of global warming produces 15% more rain instead of snow in these areas.
This not only increases the risk of floods y ground slides, but also seriously affects water availability in these regions, as it reduces the accumulation of snow that acts as a water reserve in warmer seasons.
Geographic Impact: Why Does It Rain More in the Northern Hemisphere?
An important aspect to consider is geographical distributionThe Northern Hemisphere has a greater amount of land compared to the Southern Hemisphere, which directly influences the amount of rainfall.
Because land surfaces are warming faster than oceans, they generate more convection, leading to more intense cloud and storm formation. Additionally, the thermal imbalance between the hemispheres could be shifting rain belts northward.
Oceanographic and Atmospheric Factors
Another key factor is the ocean circulationThe flow of ocean currents, particularly those from the north, also contributes to the asymmetrical pattern of precipitation. As recent studies indicate, ocean currents in the Northern Hemisphere transport heat and moisture, contributing to the formation of large storms and hurricanes.
El tropical rain belt It is also affected by the higher temperatures in the Northern Hemisphere. This increase in global temperature pushes the belt northwards, thus accentuating the asymmetry of tropical rainfall.
Extreme Rainfall and its Relationship to Elevation
The mountains of the northern hemisphere, such as the Pacific mountain ranges in North America or the Himalayas, are accentuating this trend. According to researchers from the Berkeley LabExtreme rainfall in these areas has already increased by 15% due to climate change and this rate is expected to continue to increase.
This change is alarming, since, traditionally, the snow accumulated in these mountain ranges acted as a Water reserve essential for low-lying regions during the dry season. With rain instead of snow, not only is this water availability reduced, but the risk of erosion and destruction of the mountain ecosystem also increases.
The phenomenon of asymmetry in tropical rainfall regimes is complex and multifactorial. From the influence of ocean circulation to the effects of climate change, it seems clear that the Northern Hemisphere is experiencing a significant increase in rainfall compared to the Southern Hemisphere. This situation poses crucial challenges to mitigate the impacts on agriculture, the economy and the environment.