When we think of the great rivers that shape our planet, names like the Amazon, the Nile or the Mississippi immediately come to mind. However, there is another type of "river" that is much larger and more powerful, but completely invisible to the naked eye: atmospheric rivers . These immense corridors of water vapor, carried by winds at high altitudes, play a fundamental role in the Earth's climate.
These celestial rivers, capable of moving billions of liters of water , are the source of much precipitation around the world. In California, Western Europe and Chile, they can bring beneficial rains, but also trigger devastating storms and catastrophic floods.
Long overlooked, atmospheric rivers are now better understood thanks to scientific advances and weather satellites. However, their role in the global climate remains a crucial subject of research, particularly in the face of the effects of global warming, which are making them more intense and unpredictable.
In this article, we will explore how these invisible rivers work , their impact on our climate , and the regions most affected . Finally, we will see how modern science allows us to track them and better anticipate their effects. Get ready to dive into one of the most fascinating and influential phenomena in our atmosphere! 🌍🌧️
What is an atmospheric river?
Atmospheric rivers are concentrated streams of moisture in the atmosphere that transport enormous amounts of water over thousands of kilometers. Invisible to the naked eye, they play a major role in hydrological cycles and directly influence the climate of many regions of the world.
A recent discovery by climatologists
The concept of atmospheric rivers was identified in the late 20th century thanks to advances in weather satellites and climate models. It was in 1998 that Yong Zhu and Richard E. Newell, researchers at MIT, officially used the term in a scientific publication. They demonstrated that these corridors of moisture are responsible for the majority of extreme precipitation in temperate zones of the globe (Zhu & Newell, 1998).
Comparison with terrestrial rivers
If we could look at these rivers like we do the Amazon or the Mississippi, we would be amazed by their magnitude. An atmospheric river can carry up to 15 times more water than the Amazon in the form of vapor. On average, these moisture corridors are 400 to 600 km wide and extend for thousands of kilometers , often connecting the tropics to temperate regions.
How do these invisible rivers work?
A gigantic fresh water transport network
Atmospheric rivers form when warm, moist air from the oceans is picked up by prevailing winds. This flow of water vapor then follows air currents, often along the jet stream , until it encounters an obstacle, such as a mountain range or a cold air mass. At that point, the water in these celestial rivers condenses and falls back down as heavy precipitation.
Their role in the formation of storms and precipitation
Atmospheric rivers are often the source of major storms. They can trigger intense precipitation in a short period of time, causing flash floods. For example, in California, these invisible rivers are responsible for 40% to 50% of annual precipitation (Dettinger et al., 2011). In Europe, they fuel winter storms that affect the North Atlantic.
What are their effects on our climate?
From torrential rains to extreme droughts
Depending on their trajectory, atmospheric rivers can either bring abundant precipitation or, conversely, aggravate drought when they deviate from their usual path. Thus, the absence of these moisture flows can accentuate periods of drought, as observed in California during the "Ridiculously Resilient Ridge" phenomenon between 2012 and 2016 (Swain et al., 2014).
The impact of climate change on atmospheric rivers
As the climate warms, atmospheric rivers are becoming more intense. Higher temperatures allow the air to hold more water vapor, amplifying the potential for extreme precipitation. A recent study shows that by the end of the century, the intensity of atmospheric rivers could increase by 25% to 50% (Gao et al., 2015).
Where are these celestial rivers observed?
The most affected regions of the world
The areas most impacted by atmospheric rivers are:
The west coast of the United States , particularly California and Oregon, where they are responsible for winter flooding.
Western Europe , with episodes of heavy rainfall, particularly in Spain, France and the United Kingdom.
Chile and New Zealand , where they influence precipitation in mountainous regions.
Prediction and monitoring using satellites
Thanks to satellites such as those of NASA and ESA, it is now possible to monitor these moisture flows in real time. Advanced weather models make it possible to anticipate their effects and issue alerts in the event of a major flood risk.
Conclusion: Why do we need to better understand these invisible rivers?
Atmospheric rivers are a key element of the global climate. They shape our weather and directly influence the distribution of fresh water on Earth. A better understanding of them would help us anticipate climate disasters and adapt our infrastructures to the new realities of global warming.
Scientific references
Zhu, Y., & Newell, R.E. (1998). A Proposed Algorithm for Moisture Fluxes from Atmospheric Rivers. Geophysical Research Letters, 25 (15), 2777-2780. DOI:10.1029/98GL01955
Dettinger, MD, Ralph, FM, Das, T., Neiman, PJ, & Cayan, DR (2011). Atmospheric Rivers, Floods and the Water Resources of California. Water, 3 (2), 445-478. DOI:10.3390/w3020445
Swain, D.L., Tsiang, M., Haugen, M., Singh, D., Charland, A., Rajaratnam, B., & Diffenbaugh, N.S. (2014). The Extraordinary California Drought of 2013–2014: Character, Context, and the Role of Climate Change. Bulletin of the American Meteorological Society, 95 (9), S3-S7. DOI:10.1175/BAMS-D-14-00039.1
Gao, Y., Lu, J., Leung, LR, & Yang, ZL (2015). Increased Intensity of Landfalling Atmospheric Rivers Over the West Coast of North America. Nature Climate Change, 5 (6), 632-637. DOI:10.1038/nclimate2477
Lavers, D.A., & Villarini, G. (2013). The Nexus Between Atmospheric Rivers and Extreme Precipitation Across Europe. Geophysical Research Letters, 40 (12), 3259-3264. DOI:10.1002/grl.50636