Robert C. Levy — Atmospheric Scientist

Name: Robert C. Levy

Formal Job Classification: Research physical scientist (atmospheric scientist)

Organization: Code 613, Climate Radiation Laboratory, Atmospheric Science Subdivision, Sciences Directorate

Robert C. Levy talks flying discs, elephants and “dark targets.”

What do you do and what is most interesting about your role here at Goddard? How do you help support Goddard’s mission?

I study super tiny particles in the air, known as aerosols (http://earthobservatory.nasa.gov/Features/Aerosols/), and learn about their effects on climate, air quality and health. My job is to characterize aerosol properties on a global scale, by using satellite sensors that observe reflected sunlight.

When you look out an airplane window, you see a complicated scene. You see Earth’s surface (such as trees, farms, cities, deserts or oceans); clouds (all different sizes, shapes and structures); and haze, which appears blurry and sometimes colored. The haze includes aerosols, which may be desert dust, sea salt, smoke, urban pollution or something else. I want to quantify many properties of these aerosols, including their amount and composition. And then I want to know how aerosols affect other things, like clouds, our climate, and air quality.

From an airplane, your eyes can tell you much about the scene. The issue is quantifying and translating the scene to a global scale. Satellites can provide the global view, and views in wavelengths that your eyes cannot see. Most of my data comes from a sensor known as the Moderate Resolution Imaging Spectroradiometer (MODIS), which is on two NASA satellites, Terra and Aqua. I develop algorithms, or mathematical codes, for retrieving the aerosol information from the satellite observations. We look at the entire Earth.

Is there an elephant in the lab?

Studying the atmosphere is like the story of the blind men and the elephant. In brief, several blind men touch a different part of an elephant. Each concludes that he is touching a different animal based on the particular part he touched. Our lab, the Climate and Radiation Laboratory, studies the atmosphere primarily by using remote sensing observations (from satellites, from aircraft, and from the ground). Each type of observation has strengths and weaknesses. It is only when we work together that we can reconstruct the entire elephant.

We also look not just at the elephant, but the elephant’s impact on the environment. I, along with several other Goddard scientists within and outside our lab, use different satellites, models and local observational data to study the aerosol portion. In fact, many of my fellow aerosol scientists have been profiled in this Conversations With Goddard collection.

Do you do field work?

Field experiments are especially useful to validate and interpret our satellite-derived aerosol data, especially for a particular location, season or set of conditions. NASA field experiments are often designed around the idea of flying one or more airplanes, maybe in coordination, each having many instruments to measure different atmospheric properties. At the same time, there are one or more ground sites within the region of interest. Between the aircraft and the ground sites, we can learn about the details and processes, which can only be inferred from satellite data. They provide “truth” for a satellite, and the satellite provides the “birds-eye” view for the scene.

On a typical day, we first review the weather forecast including clouds and pollution cover. Often, depending on the multiple goals of a field experiment, there are preset flight tracks for the aircraft. However, given the satellite information, we may try to steer the aircraft to measure a specific target, like a thick smoke plume from a forest fire.

It all goes back to the elephant problem. Satellites see the top, aircraft see the middle and the ground team sees the middle. Together the views form a 3-D composite view of the atmosphere.

Why did you become an atmospheric scientist?

When I was a kid, I was fascinated by weather. The family joke is my first word was “cumulonimbus.” While that probably wasn’t true, I definitely knew all the cloud types at a young age. I kept records of the days’ maximum and minimum temperatures and measured rain with a home-made gauge. I did not come from a scientific family, so I imagine my parents didn’t know what to do with me.

What’s your educational background?

I have an undergraduate degree in math from Oberlin College, a small, liberal arts college in the cornfields of northern Ohio. I believe in a liberal arts education; it definitely gave me a broad perspective and taught me how to write. I majored in math, but I earned the bulk of my credits in English, creative writing and other humanities classes. I then got a master’s degree in atmospheric science from Colorado State University.

How did you initially use your degree in atmospheric science?

I first worked at the Climate Prediction Center, a part of the National Oceanic and Atmospheric Administration (NOAA), in Camp Springs, Maryland. I was part of a larger project run by the U.S. Agency for International Development program known as the Famine Early Warning System (FEWS). FEWS still exists today. My job was to produce 10-day and monthly maps that estimated how much rain had fallen in Africa during that period. The trick was that since there were so few accurate rain gauges, we had to use all kinds of other information, including satellite data.

How did you come to Goddard?

I played a lot of Ultimate Frisbee in college and then in graduate school. While working on FEWS, I played on NOAA’s Ultimate Frisbee team. Our team played NASA’s team. One of the NASA players told me about his research group at Goddard. I now lead that research group. A few years ago, I captained the same NASA team. Although I don’t play on a team now because of family obligations, I still occasionally play in Goddard’s regular pickup games.

Why did you return to school for a doctorate?

I realized that a Ph.D. was “a union card” for scientists. With my sponsors’ blessing, I decided on a doctorate in atmospheric sciences from the University of Maryland, College Park. I worked part time and attended school part time. During that period, I was married and had two children. I will never forget working on my dissertation in a coffee shop, while rocking my infant son in his car seat on the table.

What is your major scientific contribution?

I developed the current version of the global “dark target” aerosol retrieval algorithm for satellite observations over land surfaces. When you look out an airplane window and see haze, it is much easier to see it over a “dark” surface like vegetation. The algorithm quantifies that visual contrast. The retrieved aerosol data are global, have a long history of validation, and is used for both research and operational monitoring purposes.

Goddard’s late Yoram Kaufman was the theoretical mastermind of the dark-target concept. He intuitively understood how a satellite could be used to infer aerosol properties and that it could be done on a global scale.   

Our team was and continues to be an international team. Everyone has their own favorite place to look at the data. Because I am a native of the D.C. metro area, I naturally became interested in the aerosols over Maryland. My dissertation proposal was about measuring pollution in Maryland using the MODIS satellite data.

However, before I could use MODIS aerosol data over Maryland, I had to make corrections. Our retrieval is based on knowing the properties of the underlying Earth’s surface. Yoram’s original retrieval algorithm was beautifully elegant, but needed more details. Therefore, part of my thesis involved modifying Yoram’s algorithm to better adapt to surface variations in Maryland. It turned out that my modified dark-target algorithm worked for the entire globe.  

Why was Yoram so inspiring?

He had a really good way of seeing things before anyone else did. Yet he was a very personal guy too. He had an amazing way of making you feel like you thought of a brilliant idea. Later, you realized that it was really his idea. He was very democratic. He was very much an idea person. He believed that everybody had good ideas and there was plenty of room for all of them. Science was fun for him and so it was for us too.

What is a key to success at Goddard?

Be part of things. Volunteer for things, but not too many. Be willing to collaborate. You can’t work in a vacuum.

What do you do outside of Goddard?

I live the family life. I have two kids and my wife works full time. One great thing about Goddard is the flexible atmosphere, so I can attend the kids’ sports and school events. I exercise by running, hiking, biking and just generally doing things outside. I play Frisbee when I can. And of course, I show my kids the clouds.

What’s one word or phrase that best describes you?

Curious.