Atmospheric Sciences Tribute

Roger Lhermitte (1920–2016)

This luminary in the field of weather radar did it all, from basic engineering to sophisticated analysis.

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Roger Lhermitte
Roger Lhermitte. Credit: The family of Roger Lhermitte

Roger Lhermitte, Doppler man’s Doppler man, died in Miami, Fla., on 21 November 2016 at the age of 96.

Roger initiated and quietly but ambitiously led the development of Doppler radar meteorology for 30 years. His work spanned several decades’ worth of technological advancements, beginning with his examination of precipitation particle vertical motions at a single radar resolution volume in 1959 in France and extending to the triple Doppler network that provided a four-dimensional field of air and particle motions in a 1985 thunderstorm in America.

A renowned maverick and lone worker, Roger’s formal publications for more than 20 years were exclusively single authored. In the words of his long-standing colleague David Atlas, “Roger Lhermitte is one of the brightest stars in the weather radar firmament. He can do it all, from the basic engineering to the sophisticated meteorological analysis.”

Early Career

Roger was born in Ergal, France, a small village near Versailles, on 28 May 1920. The two earliest science projects in his long career—the measurement of ozone and the development of a balloon-borne radioactive probe to measure the electric field in the atmosphere—clearly set the stage for his later work in electronics and instrumentation.

In the early stages of World War II, Roger was conscripted by the Germans to work on a radar thyratron (a high-powered electrical switch) for Siemens in Berlin. He subsequently returned to Paris for exams and opted to stay there in hiding for the remainder of the war. While in Berlin, he made numerous trips to bomb shelters for safety, an experience he likened many times to Kurt Vonnegut’s descriptions of Dresden in Slaughterhouse Five. Kurt’s brother, Bernard Vonnegut, was later to become one of Roger’s closest colleagues in atmospheric electricity.

Roger’s doctoral thesis from the University of Paris in 1954 focused on the use of radar to explore the vertical structure of precipitation. In the same year, his path crossed with Stewart Marshall’s at a conference in The Hague, Netherlands. That meeting ultimately brought Roger to America for a lifetime in radar work.

Shortly thereafter, in the winter of 1955, he visited Marshall and Walter Hitschfeld in Canada. Marshall, as head of the Stormy Weather Group in Montreal, was in close contact with David Atlas’s radar group at the Air Force Cambridge Research Laboratories (AFCRL) in Massachusetts, and in 1956, Roger was invited to visit that laboratory for 1 year. Roger, Atlas, Richard Goody (a radiation expert at Harvard), and Edwin Kessler (fresh out of meteorology studies at the Massachusetts Institute of Technology) all worked together in the cramped quarters of Great Blue Hill Observatory, where an X-band radar was also located.

Making His Mark

In 1959, Roger’s seminal Doppler work in France appeared [Lhermitte, 1959] and was based on the clever use of two antennas, one aimed at a fixed target on the ground and the other directed vertically at a storm. The mixing of the two received signals provided the Doppler frequency shift and thereby the vertical speeds of the precipitation particles. David Atlas closely followed Roger’s pioneering progress in the Doppler area, and 5 years later, Roger left France for America for the last time to join AFCRL. A major Doppler achievement arising from their work at AFCRL was the velocity-azimuth display (VAD) [Lhermitte and Atlas, 1961], which enabled the determination of wind profiles with Doppler measurements, an idea for which Lhermitte shared a patent with Atlas.

Despite the great scientific respect that Lhermitte held for Atlas, his prioritization of independence and autonomy led him away from AFCRL. After spending a year at Sperry Rand Research, he joined his former colleague from AFCRL Edwin Kessler to found the National Severe Storms Laboratory (NSSL) in Norman, Okla. Roger quickly applied the single-scanning Doppler methodology to observations of severe weather. One of his notable achievements was the identification of the Doppler velocity couplet associated with the mesocyclonic vortex, a rotating column of air located within a thunderstorm. The mesocyclone later became a main research focus of Ralph Donaldson, another former colleague of Roger’s at AFCRL, and the velocity couplet within supercell thunderstorms is widely used today with next-generation radar (NEXRAD) to identify potentially tornadic storms.

Moving Ahead

Roger was always on the move: After 3 years at NSSL, his next stop was the Wave Propagation Laboratory in Boulder, Colo., with Gordon Little, where he began the expansion from single-Doppler to multi-Doppler methods. During this period, he also extended the single-Doppler observations to wind and turbulence in the clear air.

The acquisition of a professorship in meteorology at the University of Miami in 1970 enabled Roger to apply his recently developed multi-Doppler methodology to thunderstorms. Digital signal processors fast enough to keep up with the radar scanning were needed. Roger wire wrapped these processors together, aided by dime-store glasses (Roger was very frugal). The pulse-pair processor originated from these dedicated efforts.

Now equipped with processors and multiple radars, he teamed up with Marc Gilet for the Florida Area Cumulus Experiment (FACE). He also teamed up with Marx Brook, Paul Krehbiel, Charlie Moore, and me for the Thunderstorm Research International Program (TRIP) experiment (1976–1978) at the NASA Kennedy Space Center in Florida, which continued near Socorro, N.M., in 1979. The crowning achievement of the multi-Doppler radar work was the documentation of the air and particle motions with a short-baseline triple-Doppler radar network for an isolated thunderstorm in Florida.

An Active Retirement

In his later years, long after formal retirement, Roger chose projects that were more manageable than multi-Doppler radar but that continued to produce groundbreaking results. He moved to a shorter wavelength with a small 94-gigahertz Doppler radar for observations of fair-weather cumulus clouds in the Miami area. This creative and pioneering work led to the development of similar radar systems at surface sites, on aircraft, and from a satellite to study clouds and cloud processes in a new light. This work also served as motivation for a textbook, Centimeter and Millimeter Wavelength Radars in Meteorology, that he published in 2002 at age 82.

The Miami location also enabled Roger to pursue his favorite hobby: sailing. His sailboat was moored on a canal in Coral Gables. There, Roger moved all his Doppler expertise underwater to the realm of sonar. He later collaborated with Ulrich Lemmin at the École Polytechnique Fédérale de Lausanne to investigate water turbulence with Doppler sonar methods.

When I visited Roger and his family for the last time a few months before he died, he told me with a grin that having to “fix up the radar” had become his worst recurring nightmare. The meteorological community will be forever indebted to Roger Lhermitte for fixing up so many.

Roger is survived by his wife, Corinne, and their two children, Julien and Charles. He is also survived by his former wife, Alphonsine, and their two children, Anne-Marie and Patrick.

References

Lhermitte, R. (1959), La mesure absolute des vitesses de chute des particules précipitantes a l’aide du radar, C. R. Acad. Sci., 248, 2,336–2,338.

Lhermitte, R., and D. Atlas (1961), Precipitation motion by pulse Doppler radar, in Proceedings of the Ninth Weather Radar Conference, pp. 218–223, Am. Meteorol. Soc., Boston, Mass.

—Earle Williams (email: [email protected]), Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge

Citation: Williams, E. (2018), Roger Lhermitte (1920–2016), Eos, 99, https://doi.org/10.1029/2018EO098447. Published on 22 May 2018.
Text © 2018. The authors. CC BY-NC-ND 3.0
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