Johannes Letzmann

There is no dispute about the dates. German Wikipedia, English Wikipedia and Spektrum’s Lexikon der Geowissenschaften all give the same pair: born 19 July 1885 in Wenden in Livonia, died 21 May 1971 on Langeoog. The dispute is about whose he was.

Both Wikipedias call him an Estonian meteorologist. Spektrum calls him a Livonian meteorologist of German origin. The University of Tartu’s environmental-physics history page describes him as a Latvian citizen (Läti kodanik) of Baltic German descent who was, between the wars, one of Tartu’s most prominent meteorologists. No source this page found reconciles the three labels. This page does not choose between them.

The Livonia he was born in was neither Estonia nor Latvia. It was a governorate of the Russian empire whose borders cut across both of today’s states and whose educated class spoke German. He wrote in German his whole life, worked twenty-six years in Tartu, and died on a North Sea island in a home for displaced Baltic Germans. Every label is partly right. None of them is the whole of it.

The form of his name has split the same way. The German Wikipedia article is headed “Johannes Peter Letzmann” and the Spektrum lexicon follows that three-part form; the English article is simply “Johannes Letzmann”. Estonian sources mostly have him as J. P. Letzmann. This page uses the long form where its source does.

Deutsche Wikipedia: Johannes Peter Letzmann · English Wikipedia: Johannes Letzmann · Tartu ülikool: mis eelnes keskkonnafüüsika instituudile · GEPRIS Historisch: Letzmann, Johannes Peter · Spektrum: Lexikon der Geowissenschaften, Letzmann

German Wikipedia records that Letzmann studied at the Imperial University of Dorpat from 1906 to 1913, beginning in philosophy and languages and moving to physics after a year. Seven years is a long degree. The work he is remembered for is physics, but it was written by someone who had started somewhere else.

The University of Tartu’s environmental-physics history page records that Letzmann entered the university’s service in 1913 as an assistant at the Meteorological Observatory, and was elected privatdozent — eradotsent — in 1919. The Estonian Wikipedia list of Tartu teaching staff for 1937 carries him as privatdozent of geophysics. Two years before he left he still held an unsalaried teaching appointment, not a chair.

The same page lists what he taught over those twenty years: general meteorology and climatology, the special climatology of particular regions, palaeoclimatology, oceanography, atmospheric electricity, atmospheric optics, atmospheric dynamics, aerology, terrestrial magnetism, seismology, and ultraviolet radiation and ionisation. One man, and very nearly the whole of environmental physics.

Sources do not agree about the doctorate. English Wikipedia, and an Estonian list of atmospheric-science dissertations, say the degree was awarded by the University of Helsinki in 1924. The bibliographic record of the thesis itself — in the European Severe Storms Laboratory’s reference list — gives it as a 1923 dissertation published in Tartu in the Acta et Commentationes Universitatis Dorpatensis. German Wikipedia says he took the degree at Tartu. Three sources, two cities, two years.

Deutsche Wikipedia: Johannes Peter Letzmann · Tartu ülikool: mis eelnes keskkonnafüüsika instituudile · Vikipeedia: Tartu Ülikooli õppejõudude ja ametnike loend (1937) · ESSL: severe weather reference list

The Estonian Environment Agency’s history of meteorology records that in 1918 the famous German meteorologist Alfred Wegener spent two months in Tartu, holding seminars and training sessions at the university. German Wikipedia states the consequence directly: Wegener awakened and promoted Letzmann’s interest in tornadoes — then called Großtromben — from 1918 onwards.

Wegener had the material. His 1917 book Wind- und Wasserhosen in Europa is, in the assessment of Antonescu, Ricketts and Schultz in 2019, the first modern pan-European tornado climatology: 258 reports covering 1456 to 1913, with direction of travel, speed, rotation and formation mechanism. Letzmann had what Wegener did not — the patience for the arithmetic.

The division is clear and does not need dressing up. Wegener supplied the cases and the questions; Letzmann supplied the kinematics. David Blanchard’s 2013 paper on tornado damage in the forests of northern Arizona separates the contributions concretely: among the earliest formal studies it names Wegener’s of 1917 and then Letzmann’s of 1923, and it is Letzmann it credits with working through the combinations of rotation and forward motion.

The connection held. German Wikipedia records that between 1928 and 1933 Letzmann stayed frequently with Alfred and Kurt Wegener at the University of Graz, and that in this period he described the Baltic tornado alley. English Wikipedia gives a narrower account: “Most of his studies were done at Dorpat (Tartu), but he did travel with Wegener for a year in 1928 to the University of Graz.” Alfred Wegener died in Greenland in 1930. Letzmann’s letters are in his papers at the Deutsches Museum, catalogued as Nachlass NL 001.

Estonian Environment Agency: Meteorology in Estonia · Deutsche Wikipedia: Johannes Peter Letzmann · Antonescu, Ricketts & Schultz, BAMS 100(4), 2019: 100 Years Later · Deutsches Museum: Nachlass Alfred Wegener, NL 001 · English Wikipedia: Johannes Letzmann · Blanchard, Weather and Forecasting 28(2), 2013: A Comparison of Wind Speed and Forest Damage Associated with Tornadoes in Northern Arizona

The Estonian Environment Agency’s Valgamaa climate overview calls the so-called Otepää tornado of 10 May 1920 one of the best known tornadoes in Estonia, and gives its track as roughly 35 km, running from Otepää to Lemmatsi near Tartu. Letzmann wrote it up as a 65-page monograph: “Die Trombe von Odenpä am 10. May 1920”, Acta et Commentationes Universitatis Dorpatensis A III, 1–65, 1921. Odenpä is the German name for Otepää.

Two years later came the bigger one. Heino Tooming’s conference abstract “Strong tornadoes in Estonia” gives the track of the 3 August 1922 tornado as 82 km — among the longest ever recorded in northern Europe — and classes it P4. The Environment Agency’s Jõgevamaa overview describes the path as running from the Saare and Roela area, across Mustvee and Kauksi, to Kurtna.

From this event comes the one number he timed himself. In a 2015 talk that Mati Alev reported in the Jõgevamaa newspaper Vooremaa, the climate scientist Ain Kallis said that, by Letzmann’s description, the tornado covered the 70 km from Saare to Illuka in 105 minutes. That is about 11 metres per second — the speed of the storm itself, not the speed of the wind inside it. The whole of the next chapter is built on that distinction.

Two Estonian sources end the track in different places: the Environment Agency says Kurtna, while Ain Kallis, reported in Vooremaa and citing Letzmann, says Illuka. These are different places. The map at the foot of this page marks Kurtna; Illuka now has a point of its own, and the figure below this chapter gives the distance between them.

Water gave him a third case. Heino Tooming’s earlier conference abstract, “Tornadoes in Estonia” of 2000, records that on 22 July 1928 a Captain Toom observed fifteen to seventeen waterspouts near Saaremaa, and cites Letzmann’s 1931 paper in the Annalen der Hydrographie und Maritimen Meteorologie, whose title says “Gegen fünfzehn” — about fifteen. This page has not read Letzmann’s paper itself.

Keskkonnaportaal: tornaadod · Tooming, ECSS 2002: Strong tornadoes in Estonia · ESSL: severe weather reference list · Mati Alev, Vooremaa, 11.08.2015: Jõgevamaa asub trombide teel · Tooming, Conference on European Tornadoes and Severe Storms 2000: Tornadoes in Estonia · Riigi Ilmateenistus: Valga maakonna kliimast · Riigi Ilmateenistus: Jõgevamaa kliimast

German Wikipedia records that from 1935 to 1938 Letzmann sat on the International Meteorological Organization’s committee for vortex research, and that this led directly to his drawing up guidelines for tornado research. The German meteorologist Harald Koschmieder sat on the same committee. The work was done at the Climatological Commission’s request.

The document’s full title is “Richtlinien zur Erforschung von Tromben, Tornados, Wasserhosen und Kleintromben” — guidelines for research on funnels, tornadoes, waterspouts and whirlwinds. It belongs to the session of the Climatological Commission held in Salzburg on 13–17 September 1937, and appeared in print in that session’s proceedings: Publ. 38, Leiden, Anlage XI, pages 91–110.

The same text is dated three ways in the literature, and this is not confusion but the actual state of affairs. The session was 1937, the proceedings volume appeared in 1939, and the Graz vortex research station issued a revised 32-page edition in 1944. ESSL’s reference list and the Dotzek-era literature use 1937; the Spektrum lexicon gives 1944. All three years point at something real.

What the guidelines were, Marcus Beyer of the German weather service puts briefly: a systematic handbook for observers, and with this research Germany was a pioneer worldwide. That is thirty-four years before Fujita’s scale. Peterson does not, however, call them the first — his 1992 summary says “the most extensive published guidelines”, and this page does not upgrade that.

The war cut the work short. Peterson’s 1992 abstract in Weather and Forecasting says his productivity “was essentially curtailed by the outbreak of World War II”, which came in September 1939. One trace of an American reader remains: ESSL’s reference list offers the scan of Koschmieder and Letzmann’s 1939 text together with commenting letters by J. B. Kincer, whom the list marks USWB — the U.S. Weather Bureau. This page has not read the letters.

Deutsche Wikipedia: Johannes Peter Letzmann · Peterson, BAMS 73(5), 1992: Letzmann and Koschmieder's Guidelines · Deutscher Wetterdienst: Tornadoforschung in Deutschland · Keskkonnaportaal: tornaadod · Peterson, Weather and Forecasting 7(1), 1992: Johannes Letzmann: A Pioneer in the Study of Tornadoes · ESSL: severe weather reference list · English Wikipedia: Fujita scale

German Wikipedia states that, as an ethnic German, Letzmann was forced to leave Estonia in 1939 at the outbreak of the war. The Estonian Environment Agency’s history of meteorology independently records that J. P. Letzmann worked at the University of Tartu up to 1939. Two sources, one date.

The resettlement was not his own doing. The German Wikipedia article on the resettlement of the Baltic Germans describes an operation initiated by the German Reich at the start of the Second World War, by which the Baltic Germans were largely moved from their homelands into the Polish territories the Reich had annexed. From October to December 1939 some 14 000 people left Estonia. A community that had been in Livonia for seven hundred years left over a single autumn.

Graz gave him what Tartu never had. English Wikipedia has him holding the chair of meteorology at Graz from 1939 — or 1940, the article itself hedges — until 1945, and building there the Forschungsstelle für atmosphärische Wirbel, a research station for atmospheric vortices. The Spektrum lexicon says instead that he directed the station from 1940 to 1947. Three accounts that do not line up.

In late 1945 he lost the post and the professorship was withdrawn. He stayed in Austria. German Wikipedia says that after his research funding was cut off he remained in Austria until 1969. English Wikipedia gives an earlier date: in 1962, it says, he “elected to retire to a hostel established for former Baltic Germans” on Langeoog.

Langeoog is an East Frisian island in the North Sea. The Oldenburg newspaper NWZ reports on the Baltic Germans who reached it: more than three hundred of them are buried in the dune cemetery. He died there on 21 May 1971, aged eighty-five, some 1 300 kilometres from Tartu as the crow flies, and fifty-eight years after he entered the service of the Tartu observatory.

Deutsche Wikipedia: Johannes Peter Letzmann · Deutsche Wikipedia: Umsiedlung der Deutsch-Balten · English Wikipedia: Johannes Letzmann · Estonian Environment Agency: Meteorology in Estonia · NWZ: Baltendeutsche auf Langeoog

Peterson had two outputs that year. Weather and Forecasting 7(1), pages 166–184, was titled “Johannes Letzmann: A Pioneer in the Study of Tornadoes” — the article that reintroduced him to English-speaking meteorology. Bulletin of the American Meteorological Society 73(5), pages 597–611, gave the guidelines themselves in translation with commentary. Its abstract opens by saying that the most extensive published guidelines to carrying out studies of tornadoes were written by Johannes Letzmann and Harald Koschmieder, and that they had been forgotten for decades.

The other half came from Germany. Nikolai Dotzek (1966 or 1967 – 2010 — ESSL’s own pages give his birth year both ways) moved in 1999 to DLR’s Institute of Atmospheric Physics and gathered the historical material the European Severe Storms Laboratory still keeps on its own server, among it the 1923 dissertation and a scan of the 1939 Richtlinien which, by ESSL’s reference list, carries handwritten annotations by Letzmann. In 2000 a joint paper by Dotzek, Berz, Rauch and Peterson appeared in Meteorologische Zeitschrift, reassessing what the guidelines mean for present-day tornado research.

Then the model was put to work. Holland, Riordan and Franklin in 2006 combined Letzmann’s wind field with forestry tree-stability models and simulated treefall numerically; in 2008, as David Blanchard’s 2013 paper reports it, Dotzek and colleagues pointed out that those computer runs bore out the patterns Letzmann had drawn by hand, since both rested on the same model. Beck and Dotzek published “Reconstruction of Near-Surface Tornado Wind Fields from Forest Damage” in the Journal of Applied Meteorology and Climatology 49(7), pages 1517–1537, in 2010, recovering Letzmann’s formalism and applying it to real European damage.

Estonia’s own recovery ran through Heino Tooming. His published bibliography records that Tooming returned to the study of tornadoes in pursuit of Letzmann’s legacy, and that in 1995 he organised a conference for Letzmann’s 110th anniversary. The Estonian state Environmental Portal writes that it is thanks to the American Richard Emil Peterson, the German Nikolai Dotzek, H. Tooming and other Estonian researchers that Letzmann is known worldwide.

The method is still operational, not merely historical. A German damage-analysis checklist instructs that tree directions be recorded so that they can be classified into a damage pattern according to the “Richtlinien” of Johannes Peter Letzmann, dated 1937–1939. A field form filled in today carries categories a Tartu privatdozent wrote down.

One thing has not happened. ESSL’s awards page lists the two scientific prizes presented at the European Conferences on Severe Storms: the Nikolai Dotzek Award and the Heino Tooming Award. Neither carries Letzmann’s name. The Estonian name on an ESSL trophy is Tooming’s.

Peterson, BAMS 73(5), 1992 · Beck & Dotzek, J. Appl. Meteor. Climatol. 49(7), 2010 · Blanchard, Weather and Forecasting 28(2), 2013: A Comparison of Wind Speed and Forest Damage Associated with Tornadoes in Northern Arizona · ESSL: Historical Resources · ESSL: severe weather reference list · ESSL: awards of the European Conferences on Severe Storms · Keskkonnaportaal: tornaadod · Skywarn Deutschland: Checkliste Schadensanalyse