News Excerpt:
Atmospheric river storms are forecasted in California (USA) over the next few days, dumping heavy rain and snow and raising fears of floods and mudslides.
Atmospheric rivers:
- An atmospheric river is a narrow corridor or filament of concentrated water vapour transported in the atmosphere.
- It’s like a river in the sky that can be 1000 miles long. On average, atmospheric rivers have about twice the regular flow of the Amazon River.
- Atmospheric rivers occur all over the world, most commonly in the mid-latitudes.
- These start over warm water, typically tropical oceans, and are guided toward the coast by low-level jet streams ahead of cold fronts of extratropical cyclones.
- Large-scale weather patterns and climate phenomena, such as the Madden-Julian Oscillation (MJO), also play an important role in generating AR families (Consistent atmospheric rivers).
- The Madden-Julian oscillation (MJO) is an equatorial travelling pattern of anomalous rainfall.
- It is characterised by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian Ocean and Pacific Ocean.
- When atmospheric rivers run up against mountains or run into local atmospheric dynamics and are forced to ascend, the moisture they carry cools and condenses, they can produce intense rainfall or snowfall.
Impact:
- They cause heavy rain and snow, resulting in the potential for landslides, and heavy mountain snow.
- Consecutive atmospheric rivers, known as AR families, can cause significant flooding.
