Gustav Johann Georg Hellmann or Georg Gustav Hellmann (3 July 1854 – 21 February 1939) was a German
meteorologist
A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmosphere of Earth, atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists ...
.
Hellmann was born in
Löwen (Lewin Brzeski),
Prussian Silesia
The Province of Silesia (; ; ) was a provinces of Prussia, province of Kingdom of Prussia, Prussia from 1815 to 1919. The Silesia region was part of the Prussian realm since 1742 and established as an official province in 1815, then became part ...
. Since 1907 to 1922, he was the principal of the Preußischen Meteorologischen Institut (
Prussia
Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...
n Meteorological Institute) in
Berlin
Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ...
. He died in Berlin.
Works
* An editor of the "''Meteorologische Zeitschrift''" 1892-1907 (with
Julius von Hann)
* ''Repertorium der Deutschen Meteorologie'', 1883
*
Work with snowflakes
In 1892 Hellmann piqued an interest in pictures of
snowflake
A snowflake is a single ice crystal that is large enough to fall through the Earth's atmosphere as snow.Knight, C.; Knight, N. (1973). Snow crystals. Scientific American, vol. 228, no. 1, pp. 100–107.Hobbs, P.V. 1974. Ice Physics. Oxford: C ...
s, after seeing some of
Wilson Bentley's photography, he commissioned a microphotographer to take shots of snowflakes to study. Upon review of these
microphotograph
Microphotographs are photographs shrunk to microscopic scale. s, Hellmann noted a large difference in the snowflake pictures he took, and the ones
Wilson Bentley had taken. Hellmann's snowflakes were irregular, there were various types, sizes, shapes, and forms.
Bentley's snowflakes however, were perfect, symmetrical, six-sided and reminiscent of stars. Hellmann was perplexed by this, and openly questioned the accuracy of
Bentley's work. He accused Bentley of manipulating the snowflake to get these perfect results. Bentley eventually admitted to somewhat doctoring the photographs, by scraping emulsion off the negatives, but he claimed that this did not change the integrity or accuracy of the photograph. This argument persisted for years, Hellmann insisted that altering the snowflake was unethical, as it misrepresented the snowflake in its truest form, Bentley argued the opposite. Although the argument never formally ended with one side winning, it is still Bentley's snowflake the world thinks of when they see snow fall.
Hellmann number
In Germany and especially the Netherlands, Hellmann is known for the Hellmann number, a measure for the severity of a winter. This figure is derived by adding up all negative temperatures in the period of 1 November of the previous year up to and including 31 March of the current year.
See also
*
Wind gradient
In common usage, wind gradient, more specifically wind speed gradient
or wind velocity gradient,
or alternatively shear wind,
is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. It is the rate of ...
References
External links
MeteoKust / KiteMeteo - De ultieme kustwebsite met webcams aan zeeat www.infometeo.be (about his meter; Flemish)
at home.planet.nl (about his meter; Flemish)
at fa-gem.dmg-ev.de (German)
at www.luise-berlin.de (German)
Hellmann numbers for the Bilt from 1901at knmi.nl (Dutch)
1854 births
1939 deaths
German meteorologists
Members of the Prussian Academy of Sciences
People from the Province of Silesia
People from Brzeg County
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