Atmospheric Rivers: ‘Flying Rivers’ Causing Devastating Floods

Syllabus: Geography: Atmosphere

Source: BBC

Context: Heavy rains and floods have recently affected several parts of India, killing scores and displacing thousands. These floods are exacerbated by “flying rivers,” or atmospheric rivers.

What are Atmospheric rivers?

These are long, narrow bands of water vapour in the atmosphere that transport moisture from the tropics to other regions. These “rivers in the sky” can be thousands of kilometres long and hundreds of kilometres wide, carrying large amounts of water vapour. When they make landfall, they can release this moisture as heavy rain or snow, often leading to significant flooding and other weather-related impacts.

Atmospheric rivers occur globally, affecting the west coasts of the world’s major landmasses. A well-known example is the “Pineapple Express,” a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.

The main characteristics or defining features of the Atmospheric Rivers

• A shape that is long and narrow, no more than 400 to 500 Km wide, and extending for thousands of Kilometres sometimes across entire ocean basins.

• Wind speeds of greater than 12.5 meters per second in the lowest 2 km.

• Very thick Integrated Water Vapour

• These narrow plumes of enhanced moisture transport occur in the lower troposphere in the low-level jet region (within the warm sector) of extra-tropical cyclones.

Mechanism of precipitation from Atmospheric rivers (Ars)

Heavy rainfall can result, especially when ARs make landfall because of the convergence and thus vertical uplift within an AR, and most significantly when the moisture-laden air is forced to rise over mountains. E.g. near the Rockies on the western coast of America

Impact of Atmospheric rivers in the world

ARs are a major cause of extreme precipitation and severe flooding in mid-latitude, westerly coastal regions such as the West Coast of North America, Western Europe, and the west coast of North Africa. Over 80% of flooding damages in Western USA are linked to ARs.More than 80% of all flooding damages in the Western part of the USA are associated with atmospheric rivers.

Impact of Atmospheric Rivers in India

• Eastward-moving cyclonic circulations in the northern latitudes of India in conjunction with the atmospheric rivers drawing water vapour from the lower latitudes under the circumstances of positive interference result in extremely heavy and intense precipitation over the higher reaches of northern India.

• Atmospheric Rivers result in heavy precipitation when they confront mountainous terrain, such as those found in the Himalayan ranges of North India for example: 2010, Leh in the Ladakh region of Jammu and Kashmir experienced a cloud burst, and the heavy rains that followed triggered flash floods and mudslides 2011 Kupwara District in J&K experienced heavy rainfall. Rain or thundershowers occurred in a large number of places across the country.

• 2010, Leh in the Ladakh region of Jammu and Kashmir experienced a cloud burst, and the heavy rains that followed triggered flash floods and mudslides

• 2011 Kupwara District in J&K experienced heavy rainfall. Rain or thundershowers occurred in a large number of places across the country.

A study found that between 1951 and 2020, India experienced 574 atmospheric rivers during the monsoon season, with their frequency and intensity increasing due to climate change.

Benefits of Atmospheric Rivers:

• Water Supply: Despite the hazardous effects of ARs, they can also be beneficial by providing precipitation which is essential for water supply and resources. Over the west coast of the USA, for example, ARs are thought to provide an average of 30–50% of annual precipitation and have been responsible for ending 33–74% of droughts in the region.

• Over the west coast of the USA, for example, ARs are thought to provide an average of 30–50% of annual precipitation and have been responsible for ending 33–74% of droughts in the region.

• Maintaining Hydrological Balance: Atmospheric rivers transport water vapour from the tropics to higher latitudes, redistributing moisture and supporting ecosystems and agriculture.

Way forward to deal with the challenges of atmospheric rivers

• Improving atmospheric forecasting systems should be a priority A better understanding of atmospheric rivers’ intensity, duration, and landfall locations can provide valuable information to residents and emergency responders.

• A better understanding of atmospheric rivers’ intensity, duration, and landfall locations can provide valuable information to residents and emergency responders.

• It also is important to discourage new construction in high-risk areas and help people move to safer locations after major disasters, rather than rebuilding in place.

Conclusion

As there is a direct relationship between the intensity of atmospheric rivers the climate change and they are getting stronger with the changed climate pattern, the solution lies in reducing global greenhouse gas emissions. Thus stabilizing the global climate system is the only long-term way to minimize economic damage and risk to vulnerable communities arising from the atmospheric rivers.

Mains Link:

Q1. How does the cryosphere affect global climate? (UPSC 2017)

Prelims Link:

The formation of an ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole? (UPSC 2011)

(a) Presence of prominent tropospheric turbulence; and inflow of chlorofluorocarbons

(b) Presence of prominent polar front and stratospheric clouds; and inflow of chlorofluorocarbons

(d) Increased temperature in polar region due to global warming

Ans: (b)