One observationalist looks to improve the modeling of cloud cover over stormy Southern Hemisphere seas
This is part of a series of periodic profiles on scientists who create and apply ARM data.
One day in February 2018, Roger Marchand, a research professor of atmospheric sciences at the University of Washington, found himself strapped into a seat aboard a Gulfstream V research jet. Landfall was hundreds of miles away, in Hobart, Australia.
Just 500 meters (1,640 feet) below was a patch of the Southern Ocean, a region of drizzling low clouds and white-tipped wild waves. It covers 15 percent of the Earth’s surface and is said to be the stormiest place on Earth.
“It was as bumpy as you would expect it to be,” says Marchand of the white-knuckle flight in search of cloud droplet sizes and other data on the properties of clouds and aerosols (tiny particles in the air).
What he calls an optical illusion didn’t help matters: The waves below were so large they seemed very close to the aircraft. He says, “I buzzed the pilot: ‘Are you sure we’re 500 meters up?’ ”
At the time, Marchand and other scientists were in the midst of a series of international campaigns related to the Southern Ocean, a vast, relatively pristine body of water that circles icebound Antarctica like an epic moat.
Critically, it soaks up a lot of the planet’s atmospheric carbon and radiative heat and influences global oceanic circulation and climate.
Yet the Southern Ocean is influenced by atmospheric properties that are not well understood and not well represented in models―which reflect stubbornly large biases related to cloud cover and solar radiation.
“This is not just a curiosity,” says Marchand of the knowledge gaps, “but something we really need to address.”
Scientists studying the cloud and aerosol properties of the Southern Ocean have relied mostly on satellite data, which has had little validation from direct observations.
Various international scientists designed a cluster of 2016–2018 experiments, in part, to collect validating and clarifying observations from instrumented platforms on land, at sea, and in the air.
“It is an under-observed area,” says Marchand of the reasoning behind the convergence of campaigns, “and recent scientific studies have increasingly pointed to errors and uncertainties over the Southern Ocean as a major problem. In short, the time was just right.”
He was lead scientist for one of these experiments, the Macquarie Island Cloud and Radiation Experiment (MICRE) from March 2016 to March 2018. MICRE deployed instruments at a small-island research station staffed year-round in the Southern Ocean by the Australian Antarctic Division and the Australian Bureau of Meteorology.
The MICRE field campaign was sponsored by the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) user facility, which―as it happens―Marchand first tapped for data in 1999, when he was barely out of graduate school. Since then, the Southern Ocean has increasingly gripped his attention.
“The problem is clouds,” he says, “which are much more reflective than the ocean surface,” and which hold the key to correctly predicting the amount of sunlight being absorbed over a given region. “Climate models are struggling to predict low clouds correctly over the Southern Ocean.”
About 80 percent of low clouds occur over the world’s oceans, and the Southern Ocean is exceptionally cloudy. At the same time, such clouds are the biggest source of uncertainty in modeling cloud feedback and climate sensitivity.
More Than MICRE
Joining MICRE in that cluster of recent Southern Ocean experiments was Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS), a 2017–2018 shipboard ARM campaign led by the University of Oklahoma’s Greg McFarquhar, who was then at the University of Illinois. (Marchand was a co-investigator.)
Another was the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), supported mainly by the National Science Foundation and bringing together investigators from U.S. and Australian universities and Australian meteorological agencies.
At one point, SOCRATES was intended to be the umbrella term for all the contemporaneous Southern Ocean campaigns. Its field research phase was based in Hobart, Australia, for six weeks in 2018.
SOCRATES was also supported by the Colorado-based National Center for Atmospheric Research, which supplied the aircraft that gave Marchand his dizzyingly dramatic view of high Southern Ocean waves.
In November 2019, representatives of all the campaigns gathered at the University of Tasmania in Hobart for the Southern Ocean Atmospheric Research (SOAR) workshop.
They exchanged early interpretations of data, delivered campaign presentations, and discussed quality-control progress on all the data sets.
“It was about what we saw, how to understand differences, and what’s going on,” says Marchand, who presented on MICRE.
Less than a month later, in December, McFarquhar led a session at the fall meeting of the American Geophysical Union meant to bring together researchers on matters of Southern Ocean aerosol, cloud, precipitation, and radiation studies. Marchand was a co-convener.
There will be a special issue of the Journal of Geophysical Research: Atmospheres devoted to Southern Ocean research. (Marchand, McFarquhar, and others are writing an overview article for the Bulletin of the American Meteorological Society.)
Another special issue in the same theme, with a submission deadline of March 2020, will appear in the journal Atmosphere.
Validating Satellite Data
“We observe what’s there, then we have to use our understanding of the physics and dynamics to understand how the properties we observed came to be. That part of the story is coming.”
These days, Marchand is busy using observations to change the geophysical parameters that would improve models of the Southern Ocean.
For one, he knows that low-level clouds in the region drizzle heavily. But when is that drizzle liquid water and when it is ice? (Losing ice depletes clouds and reduces their reflectivity.)
Marchand is also investigating how satellite measurements are corroborated by surface observations made during MICRE―a prelude to putting these two sources of information together.
“We observe what’s there, then we have to use our understanding of the physics and dynamics to understand how the properties we observed came to be,” he says of the physical understanding that leads to improved models. “That part of the story is coming.”
It’s too early for many papers to be out, says Marchand. But the first ones being submitted now will describe the observed cloud and aerosol properties, how these properties compare with expectations, and how they contrast with observations from the Northern Hemisphere. Other papers on the way will point out what satellites are getting right (or wrong).
After that, he speculates, a second wave of papers will focus on dynamical comparisons and on understanding the physical processes that models need to represent better to correctly predict low clouds over the Southern Ocean.
Getting to Climate and Weather
Marchand was born in Fall River, Massachusetts, and raised in the Maryland and Virginia suburbs of Washington, D.C.
He was barely out of graduate school in the late 1990s when he acquired an interest in the microphysics and modeling of the Southern Ocean―which in the last 10 years, he says, has matured into “a focus of intense effort.”
Yet, even in his last years of PhD studies in electrical engineering, Marchand’s career could easily have taken another turn.
For one, his dissertation at Virginia Polytechnic Institute and State University (B.S., 1990, M.S., 1993, PhD, 1997), with electromagnetic wave propagation investigator Gary S. Brown, was on statistically inferring the parameters of rough surfaces based on scattering data from electromagnetic waves.
But it was Marchand’s studies in electromagnetic waves that got him interested in radar systems, radar wave propagation, and scattering. By the time his PhD was in hand, he says, “I realized one of the places I could have an impact was in climate and weather.”
East, Then West
What followed was an offer from atmospheric scientist Thomas Ackerman to come to Pennsylvania State University, where Marchand was a research assistant from 1997 to 1999.
Ackerman soon moved to Pacific Northwest National Laboratory in Washington state to become chief scientist for ARM. Marchand followed him a year later as an atmospheric scientist, got acquainted with ARM data, and enjoyed life in small-town eastern Washington.
Today, Ackerman is at the University of Washington. Marchand followed him to Seattle shortly after his marriage in 2006 to Gina Massoni, who preferred big cities over little ones.
Initially, Marchand was with Ackerman at the university’s Joint Institute for the Study of the Atmosphere and Ocean (2007‒2011), and later in the Department of Atmospheric Sciences as a research professor (2012‒present).
“I like to say,” says Marchand, “that I’ve been following Tom (Ackerman) around for my whole life.”
Poetry on the Radar
The story of how Roger Marchand got to science would not be complete without telling how he got far away from science.
Marchand ripped through his undergraduate program at Virginia Tech―one of those people who thrive on 20 credit hours a quarter. But he emerged thinking that something was missing.
“I said to myself: I feel kind of robbed,” recounts Marchand. “I had this incredible slate of technical courses but missed out on the arts and humanities.”
So during graduate school―in between work on scattering models and other arcana of electrical engineering―Marchand took enough courses to earn a second bachelor’s degree (a B.A. in ancient history, in 1996) and nearly a third in classical studies. He fell six credits shy.
Along the way, Marchand studied classical Latin for four years. (“It’s the best language for poetry,” he says.)
“When you’re doing it for fun, it is tremendous fun,” says Marchand of the language of ancient Rome and the verse of Ovid and Virgil. “There’s a lot to be said for being broadly educated.”# # #
ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.