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What California’s atmospheric rivers mean for drought, floods, fires

GS Paper 1


Source: Indian Express


Context: California has experienced an exceptionally wet winter with 11 atmospheric rivers battering the state and a twelfth such storm threatening to cause even more flooding, landslides and road closures.

  • California has received 147% of average rainfall so far this season, according to the state Department of Water Resources.


About Atmospheric rivers:

  • Atmospheric rivers are vast airborne currents of dense moisture carried aloft for hundreds of miles from the Ocean and funnelled over land to fall as bouts of heavy rain and snow.


California prone to drought:

  • During any normal 20-year period of the 20th century, about 10 years were wet and 10 years were dry.
  • But in the past 25 years, only nine years were wet and 16 were dry, meaning the state needs seven more wet years to recover. And climate change points to future years that are likely to get warmer, exacerbating the increasingly dry climate.


How does the rain affect wildfires?

  • This winter’s bountiful rainfall has already triggered considerable growth in grasses and scrub that will dry out by summer, leaving a larger, thicker fuel bed for wildfires.
  • The heavy rains can create dangers around burn scars from previous wildfires. The denuded land becomes susceptible to mudslides.


Impacts on regional climate and people:

  • Heat balance: They transport huge amounts of water vapour from one place to another which is essential for the transfer of heat and equalizing heat across various latitudes.
  • Precipitation
  • Climate change: They are being amplified by global warming as they are predicted to grow longer, wetter and wider in a warming climate.
  • People:
    • Pros: In dry conditions, atmospheric rivers can replenish water supplies and quench dangerous wildfires.

They can also deliver the usually needed rainfall to a region which is necessary for human life.

  • Cons: In wet conditions, they can cause damaging floods and debris flow, wreaking havoc on local economies.
  • Visibility is also diminished as these rivers increase haze-fog conditions which harm agriculture and transport.