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.