The atmospheric rivers Atmospheric rivers (ARs) are narrow, concentrated regions of moisture in the atmosphere. These currents contain a significant amount of water vapor, which can cause significant problems in coastal regions and affect the climate of various areas around the world. In this article, we'll explore exactly what atmospheric rivers are, how they form, their impact on the environment, and the risks they can pose.
What are atmospheric rivers?
Atmospheric rivers are responsible for the horizontal transport of water vapor from the tropics to more temperate and colder regions. With a length of several kilometers and a width that can reach hundreds of kilometers, these rivers can carry quantities of water far greater than those of the largest rivers on Earth, such as the Amazon. Although they occupy only 10% of the planet's circumference, they play a crucial role in the water cycle, accounting for more than 90% of the water vapor that moves from north to south.
The formation of atmospheric rivers is intrinsically linked to weather systems, including extratropical cyclones and cold fronts. These phenomena create low-pressure conditions that facilitate the accumulation of water vapor in the atmosphere.
The moisture concentrated in atmospheric rivers comes primarily from warm ocean waters, where water evaporates and rises into the air. When this humid air moves toward cooler areas, it can condense and form precipitation.
What damage can atmospheric rivers cause?
Although many atmospheric rivers are harmless and provide beneficial rainfall, their intensity can sometimes cause serious disasters. Common negative impacts include:
- Floods: Atmospheric rivers can cause torrential rains that saturate the soil and cause flooding in affected regions.
- Ground slides: Heavy rainfall increases the risk of landslides, particularly in mountainous areas or those with unstable soils.
- Material losses: Floods and landslides can cause significant damage to infrastructure, property, and crops.
- Impact on human and animal life: In extreme cases, flooding can result in loss of human life and wildlife.
A notable case occurred on December 18, 2016, when an atmospheric river caused severe damage in the south and southeast of the Iberian Peninsula and the Balearic Islands. More than 120 liters per square meter were recorded in just twelve hours, resulting in flooding and the tragic deaths of three people.
The formation cycle of atmospheric rivers
Atmospheric rivers are a fascinating meteorological phenomenon that involves several steps in their formation:
- Evaporation: Warm ocean waters evaporate, creating water vapor that rises into the atmosphere.
- Concentration: This vapor concentrates in narrow bands as it is carried by the winds.
- Condensation: When humid air encounters a low pressure system or mountains, it cools and the vapor condenses, forming clouds.
- Precipitation: Under the right conditions, this vapor is released as rain or snow.
Examples of atmospheric rivers and their importance
Some atmospheric rivers are particularly well known for their impact on regional climate. For example, the "Pineapple Express» carries moisture from Hawaii to the west coast of the United States, causing heavy rains and snowfall that can alleviate droughts but also cause flooding.
In other parts of the world, atmospheric rivers play a fundamental role in water supply. In California, it is estimated that between 25% and 50% of annual rainfall comes from these rivers, making this phenomenon essential for agriculture and the water cycle. This precipitation is vital for filling reservoirs, supporting agriculture, and recharging aquifers.
Impact of climate change on atmospheric rivers
Climate change is affecting the dynamics of atmospheric rivers. It is expected that with rising temperatures, the amount of water vapor that these rivers can carry will also increase.This could result in more intense and frequent rainfall, as well as extreme weather events.
Scientists have observed that air temperatures have increased by approximately one degree Celsius over the last century, and they are projected to continue rising. This change could lead to a 7% increase in the air's ability to retain water vapor for every additional degree of temperature, meaning atmospheric rivers could become "wetter" and more powerful in the future.
In recent studies, it has been shown that Atmospheric rivers are responsible for up to 50% of the most extreme precipitation events that occur in many parts of the world. This includes not only flooding in coastal areas, but also droughts in other areas due to changes in rainfall patterns.
A look to the future
The future of atmospheric rivers is a matter of ongoing study. Some researchers suggest that the poleward migration of these rivers due to climate change could change the way precipitation is distributed globally, potentially causing more droughts in currently wet regions and more flooding in dry areas. Recent discoveries about the relationship between water temperatures in the Pacific and the location of atmospheric rivers are vital to predicting how they might affect different regions of the planet.
The study of atmospheric rivers is crucial for planning and mitigating their risks, as well as for understanding their role in the global water cycle. With the increasing frequency of extreme weather events, monitoring and modeling these flows is becoming increasingly important for the safety and sustainability of diverse communities around the world. It is essential to increase awareness of atmospheric rivers and their impact, not only in terms of risks but also in how they influence ecosystems and the availability of water resources.
Additional images on atmospheric rivers
