Atmospheric river primer (Part one)

This early winter has been marked in the American West with a prevalence of meteorological “atmospheric rivers”, something we’ve discussed many times in this blog in recent years, and since it ruined my early ski season, I was curious for how long this phenomenon has been a known weather factor? 

Although the term "atmospheric river" (AR) has only been part of the scientific and public vocabulary for about 30 years, the weather phenomenon itself has been documented and studied under different names for centuries. The name "atmospheric river" was coined in 1992 (and further popularized in a 1994 study) by two researchers at the Massachusetts Institute of Technology (MIT): Reginald Newell and Yong Zhu.

As both were analyzing global data from the European Centre for Medium-Range Weather Forecasts, they discovered that over 90% of the moisture moving from the tropics toward the poles was concentrated in narrow, fast-moving "filaments" that covered less than 10% of the Earth's circumference. 

Before Newell and Zhu’s naming them this way, these storms were well-known to meteorologists and residents of coastal regions, but I remember them as being called "Pineapple Express", referring to atmospheric rivers that originate near Hawaii and hit the U.S. West Coast. 

Some called them the “Warm Conveyor Belts", a term used in the 1970s to describe the flow of warm, moist air within a cyclone. Other weather forecasters called it "Moisture Plumes" or "Tropical Connections", to describe the visible bands of clouds on satellite imagery. 

The reason Newell and Zhu chose “Atmospheric river” was because these bands carried an astounding amount of water, as a single strong atmospheric river could transport roughly 15 times the average flow of the Mississippi River! Tomorrow, we’ll review the historical weather events involving this phenomenon...