astronomy

Roger Lhermitte

Roger Lhermitte is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Roger Lhermitte rather than just read about it. In short: Roger M. Lhermitte (May 28, 1920 – November 21, 2016) was a French meteorologist who "pioneered the development of meteorological Doppler radar." His career extended from the 1950s until his death where he made numerous contributions to the field of radar meteorology resulting in over 100 publications and numerous patents.

Key takeaways

Roger Lhermitte belongs to astronomy; place it in that map before memorising details.
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Reproduce the core statement of Roger Lhermitte from memory before moving on to harder problems.

Reference excerpt

Roger M. Lhermitte (May 28, 1920 – November 21, 2016) was a French meteorologist who "pioneered the development of meteorological Doppler radar." His career extended from the 1950s until his death where he made numerous contributions to the field of radar meteorology resulting in over 100 publications and numerous patents.

Early life and education Roger Lhermitte was born in Ergal, a hamlet of Jouars-Pontchartrain in the Yvelines, France, on 28 May 1920. During the occupation of Germany in France in World War II, he was compulsorily enlisted by the Germans to work for Siemens in Berlin. "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". After the end of the war, Lhermitte continued his education to pursue his doctoral thesis at the Faculté des Sciences de L’Université de Paris under the guidance of Professor Pauthenier. The subject of his thesis work was titled "Contribution à L'Étude des Précipitations Par L’analyse des Échos de Pluies Obtenus à L’aide de Radars" which, roughly translated to English was "Contributions to the study of Precipitations via the Analysis of Radar Data." The thesis begins with the sentence "La presence des gouttes de pluie d'une precipitation provoque la diffusion des ondes centrimetriques et par suite l'apparition d'echos sur les indicateurs des radars utilisant ces longueurs d'onde", which roughly translates to "The presence of precipitation provokes the scattering of centimeter wavelength radiation, which is followed by the appearance of echos on radars using this same wavelength." This is the beginning of decades long research in atmospheric science that led to over 100 publications and numerous patents.

Career

Lhermitte began his career as a scientist at "la Météorologie nationale," first in the city of Trappes, France, and later on Magny-les-Hameaux. Lhermitte first went to North America as a visitor to the Stormy Weather Group in Montreal, QC. He left Paris on January 2, 1955, arriving the next day. There he met Walter Hitcshfeld, J.S. Marshall, K. Gunn and T.East at McGill University. On that trip he met David Atlas whom he would work with in the future. The next year, he visited the Blue Hill Observatory in Boston, MA, making it his first visit to the United States. There he worked with Atlas, R. Donaldson, Edwin Kessler and others. The "early work there led to the installation of the WSR-57 radar installation network." After these two visits, went back to France and stayed there a few years.

After a few visits to North America, Lhermitte emigrated to the United States in January 1961 to work with Atlas at the Air Force Cambridge Research Laboratories (AFCRL). He left the AFCRL for the Sperry Rand Research center in New York, NY in 1963. Some of his work included exploring the use of pulsed Doppler radars to extend the capabilities of conventional Doppler radars in allowing for range discrimination. In 1964 Edwin Kessler had just become director of National Severe Storms Laboratory (NSSL) and was coordinating efforts to build a weather radar program. He had maintained contact with Roger, and reached out to him to join this new program. Lhermitte left the Sperry Rand Research center in early 1964 for this new venture to work with Kessler, K. Wilk, Dale Sirmans and others. By the end of 1964, they had completed a pulsed 3 cm radar.

In early 1967, Lhermitte left the NSSL for the Wave Propagation Laboratory (WPL) in Boulder, CO, at the request of G. Benton who was the director of ERL. He was to work with G. Little on the formation of the Wave Propagation Laboratory (WPL). In 1970, he took a position as a professor at the Rosenstiel School of Marine, Atmospheric, and Earth Science at the University of Miami. During his time at the University of Miami, he was the first to develop the 94-GHz doppler radar for the measurement of clouds. The weather radar was built in 1987. Its design and implementation is described in Lhermitte's 1987 paper "A 94-GHz Doppler Radar for Cloud Observations". The observation by Lhermitte of Mie oscillations in the 94 GHz spectrum paved the way to the measurement of drop size distributions in precipitating clouds. This was later explored by Pavlos Kollias et al. in a paper entitled "Why Mie?":The technique that we highlight in this paper represents yet another example of the visionary contributions that Dr. Roger Lhermitte has made to radar meteorogology.

Retirement Lhermitte retired as professor emeritus in the early nineties. Near the end of his career, he decided to write a book on his experiences with centimeter and millimeter wavelength radars in meteorology. It was not written to be a comprehensive review of radars in meteorology, but rather his perspective on it. It contains many original ideas developed by him. Lhermitte died on November 21, 2016, in Miami, Florida.

Contributions to the field of radar meteorology From an article on the 30th Conference on Radar Meteorology, Roger Lhermitte's contributions as listed * pioneered the development of weather radar; designed and built the first pulse-pair processor that revolutionized Doppler weather radar research; shared his pulse-pair processor design with NCAR, which made the technology available for the broad community to use; developed unique pulsed Doppler sonar for ocean current measurements; pioneered the development and demonstrated these of 3-mm radar for cloud studies (such radar will now be deployed from satellite); and pioneered multiple-Doppler radar measurements of three-dimensional kinematic fields.

30th Conference on Radar Meteorology (A Tribute to Roger Lhermitte) The 30th Conference on Radar Meteorology was held in tribute for Lhermitte, who was 82 at the time. An article in BAMS (2002) describes the tribute:

Besides the traditional banquet (see p. 1567 in the Nowcast section of this issue for the banquet speech of Rit Carbone), the conference featured a special evening event honoring Roger Lhermitte for his pioneering work in radar meteorology.

Publications

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Illustrations

Worked examples

Example 1 — a first encounter with Roger Lhermitte

Start with the simplest possible case. Write down what Roger Lhermitte claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Roger Lhermitte before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Roger Lhermitte ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Roger Lhermitte

In research: Roger Lhermitte appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Roger Lhermitte in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Roger Lhermitte is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1920 births, 2016 deaths, Doppler effects, so understanding it makes those chapters shorter.
In everyday life: Look for Roger Lhermitte outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Roger Lhermitte in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Roger Lhermitte means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Roger Lhermitte out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Roger Lhermitte in simple terms?

Why does Roger Lhermitte matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Roger Lhermitte?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Roger Lhermitte.