From: NASA Jet Propulsion Laboratory
Published May 19, 2017 02:33 PM

NASA's CPEX Tackles a Weather Fundamental

A NASA-funded field campaign getting underway in Florida on May 25 has a real shot at improving meteorologists' ability to answer some of the most fundamental questions about weather: Where will it rain? When? How much?

Called the Convective Processes Experiment (CPEX), the campaign is using NASA's DC-8 airborne laboratory outfitted with five complementary research instruments designed and developed at NASA. The plane also will carry small sensors called dropsondes that are dropped from the plane and make measurements as they fall. Working together, the instruments will collect detailed data on wind, temperature and humidity in the air below the plane during the birth, growth and decay of convective clouds -- clouds formed by warm, moist air rising off the subtropical waters around Florida.

"Convection is simply a column or bubble of warm air rising," said CPEX Principal Investigator Ed Zipser of the University of Utah in Salt Lake City. That rising air may become the seed of a rainstorm; in the tropics and subtropics, including the U.S. South, convection is the most common way for precipitation to form. Convective clouds can join together to form a major rainstorm or can even become a hurricane.

Even though convection is such a fundamental atmospheric process, the start of convection has proven difficult to predict. Bjorn Lambrigtsen of NASA's Jet Propulsion Laboratory in Pasadena, California, a member of the CPEX science team, explained why: "Tropical convection flares up quickly. A thunderstorm pops up, does its thing, and goes away in an hour or so. And they're not very large." They're typically less than six miles (10 kilometers) across. Satellites can't observe much detail about a feature that small even if they happen to be looking at the right place at the right time. "To understand what makes a thunderstorm form and grow, we need field campaigns. We need to fly to where the storms are, look at them and their environment in detail, and measure all the important features at the same time," said Lambrigtsen.

Continue reading at NASA Jet Propulsion Laboratory

Image: NASA's DC-8 airborne laboratory. (Credit: NASA / AFRC) 

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