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Image Research: William Bourke and the Spectral Transform Method

Research compiled 2026-05-12 for the upcoming NWP-history post on William Bourke and the spectral transform method in numerical weather prediction.

All candidates below have been verified via direct fetch of their Wikimedia Commons / source pages. Licenses are free-use (CC BY, CC BY-SA, CC0, or PD). Fair-use candidates are explicitly excluded as per project policy.

Summary of negative findings

  • No verifiable free photo of William Bourke exists. ResearchGate hosts his publication list but no portrait. The Bureau of Meteorology has not released a free-license portrait, and Obituaries Australia / National Library of Australia / Trove searches do not surface one. The post will need to proceed without a portrait of Bourke, or rely on a verbal portrait + an institutional photo as the visual anchor.
  • Bureau of Meteorology image archive does not appear to provide CC-licensed historical photos. The BoM website hosts material under standard Australian Commonwealth copyright; the only CC0 file on Wikimedia is the 2022 logo, which is too generic to use as a post image.
  • ECMWF imagery is NOT free-licensed. ECMWF’s terms of use require explicit permission for image reuse. Their data products are CC BY 4.0, but the imagery on their corporate site is not. Exclude all ECMWF-hosted images.
  • No Cyber 205 photograph exists on Wikimedia Commons. A Cray X-MP (the successor that ECMWF actually ran in the 1980s) is a viable substitute.
  • No vintage BMRC computer-room photo could be located under a free license.

Candidate 1: Spherical harmonics 3D visualisation (high quality, MATLAB)

  • Source page: https://commons.wikimedia.org/wiki/File:Spherical_Harmonics_deg5.png
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/b/ba/Spherical_Harmonics_deg5.png
  • License: CC BY-SA 3.0 (Creative Commons Attribution-ShareAlike 3.0 Unported)
  • Author: Dr Franz Zotter (Institut für Elektronische Musik und Akustik, Graz)
  • Date: 19 December 2013
  • Dimensions: 3,438 x 1,875 px, ~1 MB
  • Depicts: Spherical harmonics up to degree 5, plotted as 3D surfaces with alternating positive/negative lobes. Created in MATLAB.
  • Suggested filename: Spherical_Harmonics_deg5.png
  • Suggested caption (Polish): “Sferyczne harmoniki do stopnia 5 - zbior funkcji bazowych, na ktorych spektralna metoda transformacji rozwija pole meteorologiczne. Wyzsze stopnie oddaja coraz drobniejsze szczegoly. Dr Franz Zotter, CC BY-SA 3.0, via Wikimedia Commons.”

Candidate 2: Spherical harmonics overview (cleaner, fewer plots)

  • Source page: https://commons.wikimedia.org/wiki/File:Representative-spherical_harmonics.png
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/9/90/Representative-spherical_harmonics.png
  • License: CC BY-SA 3.0 + GFDL 1.2+
  • Author: P.wormer (Wikipedia user)
  • Date: 6 December 2010
  • Dimensions: 800 x 600 px, 174 KB
  • Depicts: Six 3D plots of representative spherical harmonics (Y_0^0, Y_1^0, Y_2^0 and others), each labelled with its formula.
  • Suggested filename: Representative_spherical_harmonics.png
  • Suggested caption (Polish): “Szesc reprezentatywnych funkcji harmonik sferycznych z formulami. Bourke zbudowal model atmosfery, w ktorym kazde pole - cisnienie, wiatr, temperatura - jest suma takich funkcji ze swoimi wspolczynnikami. P.wormer, CC BY-SA 3.0, via Wikimedia Commons.”
  • Note: Alternative to Candidate 1 if a smaller, less busy diagram is preferred. Use one, not both.

Candidate 3: Rotating spherical harmonics (animated)

  • Source page: https://commons.wikimedia.org/wiki/File:Rotating_spherical_harmonics.gif
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/1/12/Rotating_spherical_harmonics.gif
  • License: CC BY-SA 3.0 + GFDL 1.2+
  • Author: Cyp (2005), enhanced by Chemmix (2016)
  • Dimensions: 445 x 445 px, ~800 KB
  • Depicts: Animated GIF showing harmonics from l=0 to l=4 (rows) and m=0 to ±4 (columns), rotating around the z-axis.
  • Suggested filename: Rotating_spherical_harmonics.gif
  • Note: Animated GIFs render fine in Minimal Mistakes; this is the pedagogically clearest “what is a spherical harmonic” image in the post. Use this OR Candidate 1, not both.

Candidate 4: Gaussian grid (the actual reason for the name)

  • Source page: https://commons.wikimedia.org/wiki/File:NCEP_T62_gaussian_grid.png
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/a/a9/NCEP_T62_gaussian_grid.png
  • License: CC BY 4.0
  • Author: M. W. Toews
  • Date: 28 August 2007
  • Dimensions: 795 x 795 px, 100 KB
  • Depicts: NCEP/NCAR T62 Gaussian grid: 192 longitudes uniformly spaced, 94 latitudes unequally spaced (Gauss-Legendre quadrature points). This is exactly the kind of physical-space grid Bourke’s spectral transform method produces when it returns to grid space.
  • Suggested filename: NCEP_T62_gaussian_grid.png
  • Suggested caption (Polish): “Siatka Gaussa T62 - 192 dlugosci geograficznych rownomiernie rozmieszczonych i 94 szerokosci geograficznych rozmieszczonych zgodnie z kwadratura Gaussa-Legendrea. Tu wlasnie siatka spotyka spektrum: na tej siatce model oblicza wartosci nieliniowe, ale calkowanie wraca do harmonik sferycznych. M. W. Toews, CC BY 4.0, via Wikimedia Commons.”

Candidate 5: Latitude-longitude graticule on sphere (for comparison)

  • Source page: https://commons.wikimedia.org/wiki/File:Latitude_and_longitude_graticule_on_a_sphere.svg
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/8/83/Latitude_and_longitude_graticule_on_a_sphere.svg
  • License: Public domain (released by author)
  • Author: Peter Mercator
  • Date: 5 December 2010
  • Format: SVG (scalable, perfect for the white-frame CSS)
  • Depicts: Classic 10-degree lat-lon graticule, shown in perspective.
  • Suggested filename: Latitude_longitude_graticule_sphere.svg
  • Suggested caption (Polish): “Regularna siatka geograficzna - poludniki i rownoleznika co 10 stopni. Wlasnie ta siatka byla problemem: bieguny to osobliwosc, a punkty siatki zageszczaja sie tam tak gesto, ze krok czasowy musi byc absurdalnie krotki. Peter Mercator, public domain, via Wikimedia Commons.”
  • Use case: Pair with Candidate 4 to show “lat-lon vs Gaussian” or with Candidate 6 to show “lat-lon vs icosahedral” - the visual contrast is the point.

Candidate 6: Geodesic / icosahedral polyhedron

  • Source page: https://commons.wikimedia.org/wiki/File:Geodesic_Polyhedron.svg
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/c/c3/Geodesic_Polyhedron.svg
  • License: CC BY-SA 4.0
  • Author: Pota12
  • Date: 31 October 2021
  • Format: SVG
  • Depicts: A geodesic polyhedron (20 hexagons + 12 pentagons) - the same topology used by modern icosahedral atmospheric models (ICON, GME).
  • Suggested filename: Geodesic_icosahedral_polyhedron.svg
  • Suggested caption (Polish): “Siatka ikosaedralno-szesciokatna - dzisiejszy nastepca i siatki Gaussa, i spektralnej metody. Brak osobliwosci na biegunach, prawie jednorodne pola. Wspolczesne modele DWD (ICON) zbudowane sa wlasnie na takiej geometrii. Pota12, CC BY-SA 4.0, via Wikimedia Commons.”
  • Use case: Closing image / forward-looking visual - what came after Bourke’s spectral method.

Candidate 7: Cray-1 (Computer Museum of America, sharp museum photo)

  • Source page: https://commons.wikimedia.org/wiki/File:Cray-1_at_Computer_Museum_of_America.jpg
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/a/a8/Cray-1_at_Computer_Museum_of_America.jpg
  • License: CC BY-SA 4.0 (also available as CC BY-SA 3.0)
  • Author: Jud McCranie (Wikimedia: Bubba73)
  • Date: 11 August 2019
  • Dimensions: 6,016 x 4,016 px, ~20 MB original
  • Depicts: The iconic Cray-1 in its C-shaped cabinet with padded bench seating, at the Computer Museum of America (Roswell, Georgia).
  • Suggested filename: Cray-1_Computer_Museum_of_America.jpg
  • Note: We have used Cray-1 images in earlier posts. Check /home/michal/repos/michalbrennek.github.io/research/INDEX.md and IMAGE_SOURCE_AUDIT.md to make sure this exact file has not been used yet. If a fresh angle is needed, Candidate 7b below is an alternative.

Candidate 7b: Cray-1 (Science Museum London, alternative angle)

  • Source page: https://commons.wikimedia.org/wiki/File:Cray1LondonScienceMuseum.jpg
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/e/ea/Cray1LondonScienceMuseum.jpg
  • License: CC BY 3.0
  • Author: Cth103
  • Date: 14 March 2018
  • Dimensions: 983 x 1,751 px (portrait orientation)
  • Depicts: The Cray-1 at the Science Museum, London.
  • Suggested filename: Cray-1_Science_Museum_London.jpg
  • Note: Portrait orientation is good if a sidebar / mid-paragraph layout is wanted, since most museum Cray photos are landscape.

Candidate 8: Cray X-MP at Linköping University (1989-1993)

  • Source page: https://commons.wikimedia.org/wiki/File:Linköping_University_CRAY_X-MP.jpeg
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/c/ca/Linköping_University_CRAY_X-MP.jpeg
  • License: CC BY-SA 2.5
  • Author: Jens Ayton (Wikimedia: Ahruman)
  • Date: 7 April 2006 (photo of machine that was in service 1989-1993)
  • Dimensions: 1,024 x 640 px
  • Depicts: Cray X-MP/416 at Linköping University, Sweden - the machine ECMWF actually ran in the 1980s when Bourke’s spectral method went operational there.
  • Suggested filename: Cray_X-MP_Linkoping.jpeg
  • Suggested caption (Polish): “Cray X-MP/416 na Uniwersytecie w Linköping, w sluzbie 1989-1993. ECMWF uruchomil swoj pierwszy operacyjny model spektralny wlasnie na takiej maszynie - bo bez wektorowego superkomputera transformacja Legendrea bylaby zbyt droga, by sie oplacic. Jens Ayton, CC BY-SA 2.5, via Wikimedia Commons.”
  • Note: Strong substitute for the (unavailable) Cyber 205 - the X-MP is actually the more historically accurate machine for the ECMWF spectral story.

Candidate 9: Cray X-MP at NASA Glenn (1989, PD-USGov)

  • Source page: https://commons.wikimedia.org/wiki/File:Cray_XMP_SSD_Nasa_1989_10084.jpg
  • Direct file URL: https://upload.wikimedia.org/wikipedia/commons/b/b0/Cray_XMP_SSD_Nasa_1989_10084.jpg
  • License: Public domain (NASA work of US federal government - PD-USGov-NASA)
  • Author: NASA (uncredited photographer)
  • Date: 1 September 1989
  • Dimensions: 2,880 x 3,600 px, ~1.6 MB
  • Depicts: NASA’s Cray X-MP with Solid State Storage Device (SSD) at the Glenn Research Center.
  • Suggested filename: Cray_XMP_NASA_1989.jpg
  • Note: Higher resolution than Candidate 8 and PD-USGov is the cleanest possible license. Good alternative if a US-coded image is preferred over a Swedish one.

For a typical post layout, I suggest:

  1. Lead image: Candidate 7 or 7b - vintage Cray-1 as visual hook (the physical icon of the era when spectral methods went operational).
  2. Concept image 1: Candidate 3 (rotating animated harmonics) OR Candidate 2 (static representative harmonics) - to introduce what a spherical harmonic actually is.
  3. Concept image 2: Candidate 4 (Gaussian grid) - to show what the “Gaussian” in T62 / T106 etc. means physically.
  4. Comparison image: Candidate 5 (lat-lon graticule) - paired with Candidate 4 in the discussion of why spectral methods avoided the polar singularity.
  5. Operational machine: Candidate 8 or 9 (Cray X-MP) - when discussing ECMWF putting Bourke’s method into operational forecasting in the 1980s.
  6. Closing / forward look: Candidate 6 (icosahedral polyhedron) - what replaced spectral methods at DWD and other centres in the 2010s.

If only 4-5 images are wanted, drop either the second Cray or the icosahedral closing image.

Negative results documented (do NOT use)

  • ECMWF historical forecast charts - corporate site, not CC-licensed.
  • Bureau of Meteorology institutional photos - not on Wikimedia under free licenses. The only CC0 BoM file is the 2022 logo (generic, not useful).
  • William Bourke portrait - no free-licensed photo found anywhere (ResearchGate, Obituaries Australia, Trove, NLA, BoM staff pages).
  • CDC Cyber 205 - no Wikimedia Commons file located. Science Museum Group has a “divide panel” object but it’s an internal panel, not the machine, and licensing is not confirmed CC.
  • BMRC computer room (vintage) - no free image found.