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Why in news?

Recently, California has experienced an exceptionally wet winter with 11 atmospheric rivers battering the state since late December.

About Atmospheric rivers:

In Short – “Much like a river is water moving over land, an atmospheric river is a stream of water vapor moving in the sky”.

  • An atmospheric river (AR) is a narrow corridor or filament of concentrated moisture in the atmosphere. Other names for this phenomenon are tropical plume, tropical connection, moisture plume, water vapor surge, and cloud band.
  • Atmospheric rivers consist of narrow bands of enhanced water vapor transport, typically along the boundaries between large areas of divergent surface air flow, including some frontal zones in association with extratropical cyclones that form over the oceans.
  • Pineapple Express storms are the most commonly represented and recognized type of atmospheric rivers, the name is due to the warm water vapor plumes originating over the Hawaiian tropics that follow various paths towards western North America, arriving at latitudes from California and the Pacific Northwest to British Columbia and even southeast Alaska.
  • In some parts of the world, changes in atmospheric humidity and heat caused by climate change are expected to increase the intensity and frequency of extreme weather and flood events caused by atmospheric rivers. This is expected to be especially prominent in the Western United States and Canada.
  • Atmospheric rivers have a central role in the global water cycle. On any given day, atmospheric rivers account for over 90% of the global meridional (north-south) water vapor transport, yet they cover less than 10% of any given extratropical line of latitude.
  • Atmospheric rivers are also known to contribute to about 22% of total global runoff.
  • They are also the major cause of extreme precipitation events that cause severe flooding in many mid-latitude, westerly coastal regions of the world, including the West Coast of North America, Western Europe, the west coast of North Africa, the Iberian Peninsula, Iran and New Zealand.
  • Equally, the absence of atmospheric rivers has been linked with the occurrence of droughts in several parts of the world, including South Africa, Spain and Portugal.

What are atmospheric rivers? | National Oceanic and ...

Source: https://indianexpress.com/article/explained/explained-climate/california-atmospheric-rivers-drought-floods-fires-8511428/