Understanding How Atmospheric Rivers Control Most of Earth’s Precipitation

The rain currently pummeling coastal California is relieving parched crops. It’s also a nuisance that’s delaying flights, uprooting trees, and causing devastating flooding.

Atmospheric rivers (ARs) are to blame. These regions of humid air flow from the tropics into colder climates as strong winds, and condense when they encounter mountains. The warm air rises and cools over elevated land, forming clouds that dump rain and snow onto the earth below. ARs originate in the tropics because warm air holds more moisture.

“Atmospheric rivers are literally rivers in the sky, the rivers of water vapor that transport massive amounts of water in the atmosphere,” Marty Ralph, a hydrometeorologist, tells Popular Mechanics…To predict precipitation over the West Coast, Ralph and a co-researcher began studying atmospheric rivers. “We’re essentially measuring the atmospheric river itself over the ocean,” Ralph says. “We need to know the vertical details of the AR and [analyze] the lowest 10,000 feet.” Very little data exists on this region, because clouds tend to block ARs from a satellite’s view.

So, Air Force planes do the job; they fly into atmospheric rivers, dropping 10–12 little sensors that are about the size of a Coke can and equipped with parachutes. As they descend, the sensors measure temperature, pressure, wind, and moisture, and then communicate that data back to the airplane via radio. Next, the airplane sends the data via satellite to “a big bucket of weather data that weather prediction models around the world draw from to start the next forecast,” Ralph explains.

Meteorology has advanced so much in recent decades. It boggles the mind. Though there remains insufficient connections between informed professionals and a public which might live a safer, more productive life with more information available…in understandable form.

2 thoughts on “Understanding How Atmospheric Rivers Control Most of Earth’s Precipitation

  1. Omniscience says:

    “Before and after: See the impact of California storms from space” https://www.washingtonpost.com/weather/2023/01/21/california-storms-satellite-images/
    “After at least nine atmospheric rivers in a little more than three weeks dumped more than 30 trillion gallons of water on California, the state’s landscape of deep valleys, tall mountains and rugged coastlines has been visibly altered. Those changes, which extend well out into the Pacific Ocean, can be vividly seen from space now that the storm clouds have cleared.
    Satellite imagery from before and after the atmospheric rivers, which are narrow bands of extreme moisture that produce heavy rain and snow, tell the story of a state that has seen devastating flood damage, rising reservoirs, and billions of gallons of water lost to the ocean after a three-year drought.”

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