Photo: Erik Jepsen/UC San Diego

A Scientist's Life: Marty Ralph

Meteorologist pioneered study of atmospheric rivers impacting the western U.S.

Marty Ralph is a research meteorologist at Scripps Institution of Oceanography at UC San Diego and director of the Center for Western Weather and Water Extremes at Scripps. He earned a PhD in atmospheric sciences from the University of California Los Angeles in 1991. Ralph was a research meteorologist and branch chief in NOAA's Earth System Research Laboratory in Boulder, Colo. before joining Scripps Oceanography in 2013.

explorations now: What do you do for a living?

Marty Ralph: I'm a scientist. I combine creativity, purpose and perseverance to try to make a difference in the world using scientific methods. I strive to discover how the natural world really works, and to apply that knowledge through invention and engineering to solve real-world problems. I'm also a manager of scientists and a director of a center that provides a chance to also cultivate and mentor new scientists and engineers.

I study the part of the weather that makes storms and creates lots of rain and snow in the western U.S. One of the big things we focus on is a type of storm called an atmospheric river [AR], which is a narrow region of the atmosphere that is a couple thousand miles long, maybe 500 miles wide, but it is moving water horizontally in the form of vapor at remarkable rates. One atmospheric river on average transports, as vapor, about 25 times the water that the Mississippi River does, as liquid.

Our center focuses on the type of storms that matter most for the western U.S. in terms of extreme precipitation. The atmospheric river is a type of storm that's key for the West Coast states. We also study the summer monsoon, which is very important for the southwestern states. Those are the two main storm types we're working on right now. 

en: What are some of the main questions in your field?

MR: Some of the main questions in meteorology and atmospheric science revolve around the fate of extreme events in the future: will there be more or fewer, stronger or weaker events. Impacts of a changing climate are key to assess in that regard. So for example, in the last few years we've had both the driest year on record in parts of Northern California and two years later the wettest year on record. This was the type of change that climate models are predicting will happen more and more. So we're studying the type of storms that are most important for extremes in the West.

Another major challenge for science on the West Coast is that forecasts of the storms that provide much of the water and the snow aren't good enough for certain decisions that need to be made. We are researching how to improve forecasts of those by applying scientific methods to assess where the problems are coming from, what the problems are in the models, what data limitations might be. If we understand how these storms really work physically, and how we can improve on those things we could make better forecasts.

We're working with a number of state, local and federal agencies to try to improve our understanding and prediction of these atmospheric rivers on the West Coast. One of the key reasons we need that improvement is because the potential exists for future reservoir operations to use forecasts of atmospheric rivers to help keep some extra water to mitigate drought impacts, or to release extra water ahead of storms to reduce flood damage. We've got these major reservoirs in the west that are key to our water supply and our flood control. It’s a remarkable feat of human ingenuity that we depend upon daily.

But now we have to make even greater use of every drop of water. How can we enhance use of these existing facilities in the coming century? One way is to build in information on atmospheric river storms, which are what drive the flood risk and provide much of the beneficial water supply. We work with Sonoma County Water Agency, with Orange County Water District, the California Department of Water Resources, US Army Corps of Engineers, NASA, the US Bureau of Reclamation, and NOAA in order to try to figure out how to move forward on this problem.

en: What tools do you use in your research?

MR: One of the things we do is develop prototype tools to diagnose whether or not a storm coming in is actually an atmospheric river or just a regular storm. And if it is an atmospheric river, how strong is it going to be and is it going to have potentially more beneficial impacts or maybe a hazardous impact. We are developing a scale for atmospheric rivers to help us distinguish the most important ones from the weaker ones and be able to communicate that to the public and to decision-makers.

One of our key tools, developed in conjunction with Jason Cordeira at Plymouth State University [in New Hampshire] is an atmospheric river landfall prediction tool. It projects 10 to 14 days in the future and asks the question, what are the odds of an atmospheric river hitting a particular spot on the coast at a particular time? That tool has become quite popular and it shows very clearly when the odds are high for an AR to hit or when they're low. Now when we get out past three or four or five days, this tool may actually show odds of an AR happening, but the AR never hits because the forecasts that went into it was wrong. Sometimes an AR pops up in the forecast just 3 days before landfall, though that is more rare these days.

One of the questions we're trying to answer is what causes a forecast to go bad in terms of an atmospheric river landfall. One way to try to improve on that is to collect special observations over the ocean and data in the atmospheric rivers using research aircraft that are usually used for hurricane reconnaissance. I’ve led the creation of an experimental program called the Atmospheric River Reconnaissance Program to take these aircraft out and measure atmospheric rivers offshore before they hit. We then use those data in the forecast models to try to improve the forecast of the atmospheric river landfall position, intensity, and timing.

During an atmospheric river reconnaissance mission, two Air Force C-130 aircraft take off – one from Hawaii, one from the West Coast, and a NOAA Gulfstream jet takes off from another West Coast location. The three aircraft fly a sampling pattern of the AR offshore over about a 10-hour period. During six hours in the middle of that 10-hour period, they drop out sensors called dropsondes that measure the wind, temperature, pressure, and moisture at different altitudes below the aircraft and then radio that back to the aircraft. The aircraft sends that via satellite to the operational centers where it's incorporated into the global models in real time.

en: Why did you come to Scripps?

MR: Scripps, and UC San Diego, are world-class organizations that bring together a critical mass of know-how on topics relevant to my interests and to the needs of the region for better weather and water information. It attracts people of diverse backgrounds and interests, including some of the most talented people in their fields globally. It has a culture of creativity and risk-taking that is needed to tackle the toughest problems we face regionally and globally. As a scientist here at Scripps, coming into work each day, I know I've got a chance to make a difference in the world, at least in some small way. We do that through basic research, through development of pragmatic tools, and through testing of those tools against real-world applications.  Every day, we combine creativity with purpose to address major challenges with weather and fresh water for the West.

Related Video: Atmospheric Rivers

Sign Up For
Explorations Now

explorations now is the free award-winning digital science magazine from Scripps Institution of Oceanography. Join subscribers from around the world and keep up on our cutting-edge research.