The drought has caused some rivers in California to run dry, but some rivers are always flowing.
Not on the ground but in the sky, they are known as atmospheric rivers.
Atmospheric rivers form when very moist tropical air is carried North from near the equator and gets entrained into the jet stream.
Atmospheric rivers are part of the global water cycle and are always present somewhere on Earth at any given time.
They are typically 250 to 375 miles wide and move with the changing weather patterns.
Once this river of very moist air runs over land it first deposits heavy rain over coastal regions, then as it is forced to sharply rise over the Sierra Mountains it cools rapidly causing more condensation and resulting in very heavy snowfall.
Many atmospheric rivers are weak bringing an average amount of precipitation, but a strong atmospheric river transports an amount of water roughly equivalent to 7.5-15 times the average flow of water at the mouth of the Mississippi River.
That's just under 50 million gallons per second!
These extreme atmospheric river events can drop up to a foot of rain in California valleys in just a few days. That's as much moisture as Boise sees in an entire year.
The downside is this can cause widespread and sometimes deadly flooding. The upside is 4 to 6 feet of snow can blanket the Sierra Mountains in one of these strong events. Making for a very healthy snowpack to supply water for the following season.
On average about 30 to 50 percent of the annual precipitation on the West Coast occurs in just a few of these atmospheric river events.
Scientists continue to study this atmospheric phenomenon to improve their understanding of how they form to not only better forecast extreme weather events, but also to minimize the potential loss of life and property.
So while the devastating effects of drought continue in California, the hope is multiple atmospheric rivers will be more consistent in supplying the much-needed moisture to quench the thirst of a parched land.
