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Jacob Bjerknes (1897–1975)

Basic Information

  • Full name: Jacob Aall Bonnevie Bjerknes (known to colleagues as “Jack”)
  • Born: 2 November 1897, Stockholm, Sweden
  • Died: 7 July 1975, Los Angeles, California, USA (age 77)
  • Citizenship: Norwegian, later naturalised US (after 1940)
  • Fields: Meteorology, atmospheric science, climate science, air-sea interaction

Family Background

  • Father: Vilhelm Friman Koren Bjerknes (1862–1951), the founder of modern meteorology
  • Mother: Honoria Sophia Bonnevie (married Vilhelm 1893), a Norwegian science student in Christiania
  • Paternal grandfather: Carl Anton Bjerknes (1825–1903), professor of mathematics at the University of Christiania
  • Maternal grandfather: Jacob Aall Bonnevie, Norwegian politician and minister of education (Jack was named after him)
  • Paternal aunt: Kristine Bonnevie, Norway’s first woman professor (zoology)
  • Spouse: Hedvig Borthen (1904–1998), daughter of a well-known ophthalmologist in Bergen; married 1928
  • Children:
    • Vilhelm (“Vil”) Bjerknes, born 1931
    • Kirsten Bjerknes, born 1934
  • The Bjerknes name comes from a family farm in south-eastern Norway (Eliassen, NAS Biographical Memoir, 1995)

Jack was born in Stockholm while Vilhelm held a professorship of applied mechanics and mathematical physics at Stockholm University, then moved with the family to Christiania (Oslo) in 1907, and to Leipzig in 1913. Jack stayed behind in Christiania to finish junior college and begin science studies at the University of Kristiania before rejoining his father in Leipzig in 1916.

Education

  • Junior college (“gymnasium”) in Christiania (now Oslo)
  • University of Kristiania (now Oslo) – mathematics and physics, from ~1915
  • 1916: interrupts his studies to travel to Leipzig to assist his father at the Geophysical Institute
  • Ph.D. from the University of Oslo, awarded in 1924 for his 1922 paper on the diagnostic and prognostic application of mountain observations, investigating sloping frontal surfaces using Swiss Alpine data (Geofys. Publ. III(6); Eliassen, 1995)

Career Timeline

Period Position Institution
1916–1917 Research assistant to his father (age 19) Leipzig Geophysical Institute
1917–1918 Assistant meteorologist Bergen Geophysical Institute
1918–1920 Weather forecaster in Bergen during WWI-era “agriculture” forecasting service Bergen
1920–1931 Head, Weather Forecasting Office for Western Norway Bergen
1922 Invited consultant, Swiss Meteorological Institute Zurich
1926 Support meteorologist for Amundsen’s Norge Arctic airship flight –
1931–1939 Professor of meteorology, chair established for him Geophysical Institute, Bergen Museum
1933–1934 Visiting lecturer Massachusetts Institute of Technology
July 1939 Departed Norway with family for an “eight-month lecture tour” of the United States –
April 1940 Stranded in America after German invasion of Norway –
1940–1945 Professor of meteorology and head, Section of Meteorology, Dept of Physics UCLA
1940–c.1946 Training school for US Army Air Corps weather officers UCLA
1945 New Department of Meteorology established at UCLA (per Eliassen memoir; the department records also give 1946) UCLA
1945–1965 Chairman, Department of Meteorology UCLA
1948–1951 President, Meteorological Association, International Union of Geodesy and Geophysics (IUGG) –
1965–1975 Professor Emeritus, UCLA UCLA

(Sources: Eliassen, NAS Biographical Memoir, 1995; Holmboe, Namias & Wurtele, UCLA In Memoriam, 1977.)

The Bergen School Years (1917–1939)

(Extensively covered in the blog’s Bergen School posts of 26–28 March 2026.)

The convergence lines (1916–1917)

In Leipzig, Jack took over a research project on convergence lines in the wind field started by a German doctoral student, Herbert Petzold, who had been killed at Verdun in 1916. He showed that convergence lines may be thousands of kilometres long, tend to drift eastwards, and are connected with clouds and precipitation. His first scientific paper Über die Fortbewegung der Konvergenz- und Divergenzlinien (Meteorol. Z., 1917, pp. 345–49) appeared before he was twenty (Eliassen, 1995, p. 5).

The 1919 cyclone paper

In 1917, when the Leipzig institute faltered under WWI shortages, the family moved to Bergen (via Vilhelm’s new professorship, arranged through Fridtjof Nansen and Bjørn Helland-Hansen). Jack and Halvor Solberg were Vilhelm’s two junior assistants. With wartime severance from Atlantic observations, they built a tenfold-denser observing network across southern Norway. Jack was assigned to the map desk in Bergen and Solberg in Christiania.

In the summer of 1918 Jack identified his old Leipzig convergence lines – which he now termed fronts – moving across Norway, and connected them systematically to cyclones. His paper “On the Structure of Moving Cyclones” (Geofysiske Publikasjoner I(2), published 1 February 1919, eight pages) laid out the frontal cyclone model: warm and cold air masses separated by sloping frontal surfaces, warm air ascending to produce cloud and precipitation bands, and cyclones organising the exchange of air between polar and equatorial regions.

Eliassen (NAS memoir, 1995): “On the whole, Jack’s short paper of eight pages contained an abundance of very interesting thoughts and suggestions. It was a fantastic achievement for a twenty year old after a few months of work with weather maps from a limited part of Europe.”

Polar front theory, occlusion, and the life-cycle model

The “Bergen team” (Jack, Solberg, and from 1919 the Swedish student Tor Bergeron) refined the model. Solberg re-analysed old Atlantic weather maps from ships and showed the polar front existed as an undulating line across the ocean. Bergeron discovered occlusion: the cold front overtakes the warm front, lifting the warm-sector air aloft. Theodor Hesselberg summarised the result: the cyclone “is born as Solberg’s initial wave on the polar front, develops into Jack Bjerknes’s ideal cyclone, and finally suffers the Bergeronian occlusion death” (quoted Eliassen, 1995, p. 9).

The 1922 Bjerknes–Solberg paper “Life Cycle of Cyclones and the Polar Front Theory of Atmospheric Circulation” (Geofys. Publ. III(1), 1923) integrated the cyclone model with the northward heat-transport mechanism.

Bergen Weather Service director and the upper wave

  • 1920: appointed head of the Weather Forecasting Office for western Norway
  • 1922: Zurich consultancy verified sloping fronts up to 3 km using Alpine peak-observatory data
  • 1924: Oslo Ph.D. awarded
  • 1928: married Hedvig Borthen; built a house in Hop, south of Bergen, on a lot from Hedvig’s father
  • 1928 December: P. Jaumotte’s thirty-one instrumented balloons over Uccle, Belgium, were analysed by Jack. The resulting paper contained “probably the first description of the waves in the upper- tropospheric westerlies, which are connected with the cyclones at low levels” (Eliassen, 1995, p. 10). The paper correctly identified vertical stretching as the vorticity source.
  • 1931: relinquished leadership of the Weather Forecasting Office to Sverre Petterssen and took up a newly-established professorship in meteorology at the Bergen Museum (the forerunner of the University of Bergen).
  • 1937: Bjerknes paper pointed to the meridional gradient of the Coriolis parameter as an important quantity in the dynamics of upper waves – work that “inspired Carl-Gustaf Rossby to derive his celebrated wave formula” (Eliassen, 1995, p. 11).
  • 1933–34: visiting lecturer at MIT, where Rossby had built up the first American meteorology department.

The 1939 American Lecture Tour and the Exile

In July 1939 Jack Bjerknes, his wife Hedvig, and their two children (Vil, 8; Kirsten, 5) left Norway for what was “supposed to be an eight-month lecture tour to the United States” (Eliassen, 1995, p. 11; UCLA In Memoriam, 1977: “On an extended visit to America in 1940, he found himself stranded when Norway was invaded by the Germans”).

The tour was well-planned: Jack had American contacts from his 1933–34 MIT stay, strong standing in the meteorological community, and a general invitation from several universities. He had already lectured in Switzerland, England, the Netherlands, Germany, Canada, and the US as “an invited guest lecturer” (Eliassen, p. 11).

The timeline in Europe tipped the visit into permanent exile:

  • 1 September 1939: Germany invades Poland; Britain and France declare war.
  • 9 April 1940: Germany invades Norway and Denmark. The Bjerknes family decides to remain in America. Vilhelm, Jack’s father, stayed in occupied Oslo and survived the war, dying of heart trouble in Oslo on 9 April 1951 – exactly eleven years to the day after the German invasion. Hedvig Bjerknes recalled that Jack chose the UCLA campus for his new assignment “in order to be near the Scripps Oceanographic Institution in La Jolla; he was of the opinion that cooperation with oceanographers was important” (Eliassen, 1995, p. 12, as told by Mrs Bjerknes).

The American weather-training mobilisation followed almost immediately: Jack was asked to establish an Army Air Corps weather-officer training school at UCLA. Jörgen Holmboe (already at MIT with Rossby since 1936) joined him; together they formed the Norwegian-accented core of the new Section of Meteorology inside UCLA’s Department of Physics.

Founding the UCLA Department of Meteorology (1940–1946)

Jack joined the UCLA faculty in 1940 as Professor of Meteorology and head of a new Section of Meteorology within the Department of Physics. Joseph Kaplan, the UCLA physicist, helped make the administrative arrangements.

  • 1940–45: Section of Meteorology inside the Physics Department; WWII military weather training the primary purpose. Over 1200 meteorologists were trained at UCLA for the war effort (see Holmboe.md); Jack and Holmboe and Morris Neiburger taught the courses.
  • 1945 (per Eliassen) / 1946 (per department records): independent Department of Meteorology established with Jack as chairman.
  • Early colleagues: Jörgen Holmboe (Bergen School, brought by Jack); Morris Neiburger (American; trained at Caltech); Joseph Kaplan (physicist, supported the department’s creation); later Yale Mintz (from 1950), James London, S. V. Venkateswaran.
  • First doctoral cohort: Jule Charney (Ph.D. 1946) and Yale Mintz (Ph.D. 1949) – the two “first UCLA meteorology Ph.D.s” (see Yale_Mintz.md for the Mintz–Arakawa GCM story). Jacob Bjerknes was Mintz’s advisor; Holmboe was Charney’s advisor, with Jack as co-supervisor.

Wartime service

Jack served in a paid-consultant / uniformed capacity to the US Army Air Corps. Eliassen: “During the war, Jack visited England, Italy, Hawaii, and Guam as a consultant to the U.S. Army Air Corps.” He was awarded the Meritorious Civilian Service Medal by the US Air Force in

  1. A widely cited detail (Wikipedia, citing Dagbladet Magasinet, 11 February 2014) says that as a US Air Force colonel Bjerknes helped determine the best weather windows for the atomic bombings of Hiroshima and Nagasaki. Flag: not independently verified in the Eliassen memoir or the UCLA In Memoriam, both of which only mention the wartime travel and the Meritorious Civilian Service Medal. The 1995 Eliassen memoir is the most authoritative source and does not make the Hiroshima/Nagasaki claim.

The Jeffreys / General Circulation Project (1947–1960)

Jack’s research in the 1940s and 1950s focused on the general circulation of the atmosphere. The English geophysicist Harold Jeffreys had proposed in 1933 that angular momentum is transferred from low to middle latitudes by atmospheric waves and eddies, maintaining the jet streams against surface friction.

Eliassen (1995, p. 13): “Based on Jeffreys’s theory, Jack Bjerknes started a major research project on the general circulation of the atmosphere. His principal co-worker was Yale Mintz; but invited scientists from many countries participated. They collected data from the entire northern hemisphere and calculated meridional fluxes of angular momentum and energy and many other statistics. The results verified Jeffreys’s thesis and were in reasonable agreement with results from Victor Starr and his group at MIT, who ran a similar project at the same time.”

This “UCLA General Circulation Project” was the observational predecessor to the Mintz–Arakawa GCM of the 1960s. The data required was huge; Mintz “orchestrated an army of student helpers and amateur programmers to feed a prodigious amount of data through paper tape to SWAC” – UCLA’s first computer (UCLA In Memoriam for Mintz, 1993; see Yale_Mintz.md). Jack’s 1944 paper with Holmboe, “On the Theory of Cyclones” (J. Meteorol. I(1)), was the theoretical anchor – and the paper that Charney would unknotted with his 1947 quasi-geostrophic theory of baroclinic instability.

North Atlantic Sea-Surface-Temperature Studies (Late 1950s)

Toward the end of the 1950s, as Eliassen puts it, “when Jack Bjerknes was around sixty, he turned his mind to a new field of research that engaged him for the rest of his life – the interaction of atmosphere and sea” (1995, p. 13).

Three men are credited by Jack as his inspiration: C. G. Rossby, H. U. Sverdrup, and Bjørn Helland-Hansen. All three died in 1957, the year Jack began his oceanographic work.

His first studies concerned the North Atlantic:

  • He found that the 20th-century warming of the North Atlantic could be explained by an increased wind drag that speeded up the Gulf Stream (Bjerknes, 1959, “The recent warming of the North Atlantic”, in Bolin ed., The Atmosphere and Sea in Motion – Rossby Memorial Volume).
  • He showed that inter-annual variations of North Atlantic sea-surface temperature were connected with the strength of the mid-latitude westerlies: stronger westerlies implied cold anomalies south of Iceland/Greenland and warm anomalies in the Gulf Stream near the Grand Banks (Bjerknes, 1962, Geofys. Publ. XXIV(3); 1964, Atlantic Air-Sea Interaction, Advances in Geophysics 10:1–82).

These studies established the pattern – now standard – of mid-latitude SST anomalies responding to wind-stress anomalies, with the ocean behaving as a slow-responding heat reservoir rather than an autonomous driver.

The 1957–58 El Niño and the Tropical Pacific

The 1957–58 El Niño coincided with the International Geophysical Year (IGY), producing the first densely observed tropical Pacific warming in history. Combined ocean and atmosphere observations showed a remarkable basin-scale warming extending westwards from South America, not the coastal anomaly off Peru that had been assumed.

Bjerknes used this event as his first tropical Pacific case study. His 1961 paper “El Niño, Study based on analysis of ocean surface temperatures 1935-57” (Bull. Inter-Am. Tropic. Tuna Comm. V(3): 219–303) was based on fisheries-agency SST time series. He realised that:

  1. El Niño is not a local Peruvian phenomenon but a basin-scale oscillation affecting the atmosphere and ocean over the entire tropical Pacific.
  2. During El Niño years, the eastern and central equatorial Pacific can be ~2 K warmer than normal across an enormous area.
  3. Such anomalies must represent a major heat and moisture source for the atmosphere.

(Eliassen, 1995, pp. 14–15; ENSO Review, “1957-1958 El Niño event”.)

The 1966 Tellus Paper

Bjerknes, J. (1966). “A possible response of the atmospheric Hadley circulation to equatorial anomalies of ocean temperature.” Tellus XVIII(4): 820–829.

Abstract (verbatim, Tellus landing page)

Weakness and temporary elimination of the equatorial easterly winds over the eastern and central Pacific in late 1957 and early 1958 brought about a brief cessation of equatorial upwelling which in turn caused the occurrence of above-normal surface water temperatures in the tropical Pacific from the American coast westward to the dateline. This sudden introduction of a large anomalous heat source for the atmosphere intensified its thermodynamic circulation, especially in the wintertime (northern) hemisphere. Record intensity of the westerlies resulted in the eastern North Pacific. The anomalous depth of the Low in the Gulf of Alaska had the downwind effect of weakening the Iceland Low and setting the stage for a cold winter in northern Europe.

Why this paper matters

This is the paper that proposed:

  1. Equatorial Pacific SST anomalies can drive the atmospheric Hadley circulation (not merely respond to it).
  2. Tropical forcing can have extratropical teleconnection consequences – the Gulf of Alaska Low, the Iceland Low, cold European winters.
  3. The causal chain starts with trade-wind weakening, flows through reduced upwelling, produces the warm SST anomaly, and propagates poleward as an anomalous Hadley-cell strength.

The 1966 paper was a single-case analysis (the 1957–58 event). It did not yet make the full El-Niño/Southern-Oscillation link – that came in 1969 after the 1963–67 data-rich period.

The 1969 Monthly Weather Review Paper

Bjerknes, J. (1969). “Atmospheric teleconnections from the Equatorial Pacific.” Monthly Weather Review 97(3): 163–172.

  • DOI: 10.1175/1520-0493(1969)097<0163:ATFTEP>2.3.CO;2
  • Open-access copy (Harvard EPS 281r course): https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/ENSO/Bjerknes-1969.pdf
  • AMS journal page: https://journals.ametsoc.org/view/journals/mwre/97/3/1520-0493_1969_097_0163_atftep_2_3_co_2.xml
  • ADS record: 1969MWRv…97..163B

What the 1969 paper argued

Bjerknes built on his 1966 case and used the 1963–67 observations to generalise the story:

  1. The Walker Circulation. He proposed that the atmosphere over the tropical Pacific overturns zonally (east-to-west): air rises over the warm west Pacific, flows east at height, sinks over the cold east Pacific, and returns westward at the surface as the trade winds. He named this circulation after Sir Gilbert Walker, who had discovered the Southern Oscillation – the pressure see-saw between the Indo-Australian low and the South Pacific high – in the 1920s. Bjerknes’s quote from the paper: the circulation “must be part of the larger ‘Southern Oscillation’ statistically defined by Sir Gilbert Walker.”
  2. The El-Niño/Southern-Oscillation link. He showed that the pressure oscillation (measured at Darwin vs Tahiti/Easter Island) and the SST oscillation (Nino-3 area vs West Pacific warm pool) are two signatures of a single coupled oscillation.
  3. Teleconnections. He documented how the 1957–58, 1963–64, and 1965–66 warm events all produced the same pattern of strengthened North Pacific westerlies, deeper Aleutian Low, and downstream effects on North American and European weather.

  4. The feedback. The paper’s most-quoted passage (p. 171):

    “This chain reaction shows that an intensifying Walker Circulation also provides for an increase of the east-west temperature contrast that is the cause of the Walker Circulation in the first place.”

    This is the first explicit statement of what is now called the Bjerknes feedback (see next section).

The Bjerknes Feedback

The positive feedback loop between the ocean and atmosphere in the equatorial Pacific, now universally called the Bjerknes feedback:

  • Start: Trade winds weaken for some reason.
  • Reduced surface stress → reduced upwelling of cold water in the eastern equatorial Pacific.
  • Reduced upwelling → warmer SST in the east.
  • Warmer east-Pacific SST → reduced east-west SST gradient.
  • Reduced SST gradient → reduced east-west pressure gradient.
  • Reduced pressure gradient → further weakening of the trade winds.

(The reverse loop – strengthening trades → more upwelling → colder east → stronger gradient → stronger trades – drives La Niña.)

Every coupled ocean-atmosphere model of ENSO in 2026 – from the Zebiak–Cane intermediate model (1987) through the modern CMIP GCMs – rests on the Bjerknes feedback as its core instability. See for example the IRI/LDEO climate data library’s description: https://iridl.ldeo.columbia.edu/maproom/ENSO/New/bjerknes.html

Later Work (1970–1975)

Jack continued working on tropical Pacific air-sea interaction throughout his emeritus period.

  • 1972: “Large-scale atmospheric response to the 1964-65 Pacific equatorial warming,” J. Phys. Oceanogr. 2(3): 212–17.
  • 1972: “Global ocean-atmosphere interaction,” in Rapports et Procès-Verbaux, International Council for the Exploration of the Sea, vol. 162, pp. 108–199.
  • 1974: Final NSF report “Atmospheric Teleconnections from the Equatorial Pacific During 1963-67.”

Eliassen (p. 16): “Jack Bjerknes was active as a scientist for more than fifty-five years. […] His waking hours were devoted to work and studies of his problems, never in a great hurry but never stopping.”

Personal Life, Personality, Teaching

At home

Jack and Hedvig lived in Santa Monica during the UCLA years. They also kept the house in Hop outside Bergen and “often spent their holidays in Norway” (Eliassen, 1995, p. 16). Jack “held contact with Norwegian colleagues, many of whom were invited to UCLA as visiting scientists” – including Arnt Eliassen (who would write the NAS memoir), Ragnar Fjørtoft, Einar Høiland, and of course Jörgen Holmboe (permanently on the UCLA faculty).

Personality

Eliassen (NAS memoir, p. 15–16):

“Jack Bjerknes was a modest and kind man, always generous with his time to listen to the problems of students and colleagues and always comforting them with his wise counsel and guidance. But he never wasted his time. His waking hours were devoted to work and studies of his problems, never in a great hurry but never stopping. He was very persistent; when he took up a problem, he would not let go of it until he had done his utmost to have it clarified.”

The UCLA In Memoriam by Holmboe, Namias, and Wurtele (1977) says:

“Father and son worked together almost as a single personality, possessing the faculties of both the theoretical and the empirical scientist. This combination may be a clue to the great break-through in Bergen. […] With intuition and rare insight, he was able to reveal the essential physical mechanism that governs the evolution of these waves and their coupling with the surface lows.”

Fjørtoft’s verdict

As quoted in the UCLA In Memoriam (1977), Ragnar Fjørtoft, director of the Norwegian Meteorological Service and a member of Charney’s 1950 ENIAC forecast team:

“He contributed perhaps more than any other meteorologist who has ever lived to create order in our knowledge of the atmosphere.”

Honours and Distinctions

Award Year
Honorary Fellow, Royal Meteorological Society 1932
Member, Norwegian Academy of Science and Letters 1933
Member, Royal Swedish Academy of Sciences 1933
Symons Gold Medal, Royal Meteorological Society 1940
William Bowie Medal, American Geophysical Union 1945
Meritorious Civilian Service Medal, US Air Force 1946
Knight 1st Class, Royal Norwegian Order of St. Olav 1947
President, Meteorological Association, IUGG 1948–1951
Vega Medal, Swedish Society of Geography 1958
International Meteorological Organization (IMO) Prize, WMO 1959
Carl-Gustaf Rossby Research Medal, AMS 1960
Robert M. Losey Award, Institute of Aerospace Sciences 1963
National Medal of Science (USA) 1966
Honorary Member and Fellow, American Meteorological Society 1966
Golden Plate Award, American Academy of Achievement 1967
Honorary Doctor of Laws, University of California 1967

Elected to: Royal Norwegian Academy of Sciences; Royal Swedish Academy of Sciences; Danish Academy of Technical Sciences; Academy of Sciences (India); American Academy of Arts and Sciences; US National Academy of Sciences.

The AGU Jacob Bjerknes Lecture – the Atmospheric Sciences Section’s flagship named lecture – was established in his memory.

Honours not on most lists (verification status)

  • Foreign Member, Royal Society (ForMemRS). The task prompt mentioned Jacob as a ForMemRS. Flag: not confirmed. The NAS memoir lists only the academies above; Vilhelm Bjerknes was ForMemRS (1933). This is the likely source of confusion.
  • Presidential Medal of Freedom: the UCLA In Memoriam refers loosely to “the Presidential Medal” – this is the National Medal of Science (1966), not the Medal of Freedom.

Death and Burial

Jack Bjerknes died in Los Angeles on 7 July 1975, aged 77. The Santa Cruz Sentinel (8 July 1975, p. 24) carried a brief wire obituary under the headline “Weather Forecast Pioneer Dies”. He is survived in the family record by his wife Hedvig (who died in 1998, age 93), son Vil (b. 1931), and daughter Kirsten (b. 1934).

A memorial volume, M. G. Wurtele (ed.), Selected Papers of Jacob Aall Bonnevie Bjerknes (Western Periodicals Co., North Hollywood, CA, 1975) was prepared with a complete bibliography.

Connections to Other NWP/Climate Pioneers

  • Vilhelm Bjerknes (father; see Vilhelm_Bjerknes.md). The two worked “as a single personality” in Bergen 1917–1926. Vilhelm’s 1904 programme + Jack’s 1918–19 observations = the Bergen School.
  • Carl-Gustaf Rossby. Rossby was a junior member of Vilhelm’s Bergen team in the early 1920s before emigrating to the US. He became the dean of American meteorology at MIT and then Chicago; his 1939 wave formula was “inspired” (Eliassen) by Jack’s 1937 paper on meridional vorticity gradients. Rossby died in 1957 – the same year Jack turned to the Pacific.
  • Tor Bergeron. Swedish; joined the Bergen team 1919; discovered occlusion.
  • Halvor Solberg. Norwegian; Jack’s co-forecaster in Christiania 1918; co-author of the polar-front paper 1922.
  • Sverre Petterssen. Norwegian; took over the Bergen Weather Service in 1931 when Jack moved to the Bergen Museum chair. Later emigrated to the US (MIT, then Chicago).
  • Erik Palmén. Finnish; collaborator with Jack on upper-air cyclone structure in the 1930s.
  • Harold Jeffreys. English geophysicist; his 1933 angular-momentum theory was the starting point for Jack’s 1947–60 UCLA General Circulation Project.
  • Gilbert Walker (1868–1958). English mathematician and director- general of Indian observatories; discovered the Southern Oscillation (1923–28). He died in 1958 at age 90, just as Jack was starting his tropical-Pacific work. There is no evidence they ever met; Jack named the Walker Circulation after Walker in 1969, eleven years after Walker’s death.
  • Jörgen Holmboe (see Holmboe.md). Bergen-School Norwegian; Jack’s co-founder of the UCLA department; Charney’s doctoral adviser.
  • Yale Mintz (see Yale_Mintz.md). Jack’s Ph.D. student (1949); his principal collaborator on the General Circulation Project; later founder of the UCLA general-circulation modelling programme with Akio Arakawa. Jack hired Mintz to the faculty in 1950 and authorised the Mintz–Arakawa GCM project in 1961, even though (per Arakawa’s 1997 AIP oral history) several senior colleagues thought it “far too ambitious.” The direct lineage from the Bergen School through Jack to the Mintz–Arakawa GCM is unbroken.
  • Jule Charney (see Charney.md). The UCLA department’s first Ph.D. (1946). Holmboe was Charney’s adviser; Jack was co-supervisor. Charney was recruited into meteorology by Holmboe’s seminar in 1940–41. Charney’s 1947 baroclinic-instability theory solved the problem Jack and Holmboe had worked on in their 1944 paper “On the Theory of Cyclones.”
  • Bjørn Helland-Hansen. Norwegian oceanographer; Jack’s Bergen colleague for twenty years; died 1957. Jack credited Helland-Hansen (with Rossby and Sverdrup) as his primary inspiration for turning to air-sea interaction.
  • H. U. Sverdrup. Norwegian oceanographer; Vilhelm’s former Carnegie assistant in Leipzig; later director of Scripps; died
    1. Chose UCLA for proximity to Scripps (Hedvig Bjerknes’s testimony to Eliassen).
  • Jerome Namias. American synoptician and long-range forecaster; co-author of the UCLA In Memoriam; his 1960 paper on the 1957–58 Pacific meteorology was cited in Jack’s 1966 Tellus paper.
  • Arnt Eliassen. Norwegian; one of Charney’s collaborators on the 1950 ENIAC forecast; later wrote the NAS Biographical Memoir of Jacob Bjerknes (1995).
  • Morton G. Wurtele. UCLA Norwegian-school inheritor; editor of Jack’s Selected Papers (1975); co-author of the UCLA In Memoriam.

Legacy and the “Man and the Machine” Arc

Jack Bjerknes is one of the very few twentieth-century scientists to have made two paradigm-shifting contributions separated by half a century:

  1. 1919: the Norwegian cyclone model, which made synoptic weather forecasting possible and remains the conceptual basis of every weather map in 2026.
  2. 1969: the Bjerknes feedback and the El-Niño/Southern-Oscillation coupling, which created climate dynamics as a sub-field and underpins every ENSO model today.

The father-son arc is stark:

  • Vilhelm (1862–1951) treated the atmosphere as a closed system of hydrodynamic equations that could in principle be integrated forward in time.
  • Jack (1897–1975) showed first that the atmosphere’s mid-latitude weather is organised by the polar front, and second that the atmosphere is not closed at all – it is one compartment of a coupled ocean-atmosphere machine whose tropical oscillations control weather half a world away.

Between them, father and son defined the scope of twentieth-century dynamical meteorology: start with the equations, add the weather fronts, add the ocean, keep adding. The UCLA department Jack founded in 1940 became the nursery of the world’s first global GCM (Mintz–Arakawa, 1964) and of ENSO dynamics (Bjerknes, 1969). Both were direct continuations of the Bergen programme, transplanted 9000 km west.

Jack Bjerknes was Mintz’s Ph.D. advisor; Mintz’s GCM with Arakawa was the direct descendant of Jack’s 1947–60 General Circulation Project; the Mintz–Arakawa code became the backbone of the UCLA, NASA/GISS, and UCLA-derived climate models of the 1970s and beyond (see Yale_Mintz.md).

Anecdotes for Blog Use

  1. The peripatetic childhood. Born in Stockholm (1897), moved to Christiania (1907), stayed alone in Oslo at sixteen when the family moved to Leipzig (1913), joined them at nineteen in wartime Leipzig (1916), and finally settled in Bergen at twenty (1917). Jack’s entire upbringing was a Nordic-German-Swedish scientific diaspora.

  2. The dead German student’s notebook. The first research project of Jack’s career – convergence lines – he inherited from Herbert Petzold, a doctoral student at Leipzig “sent to the front and killed at Verdun in 1916” (Eliassen, p. 5). The resulting paper, Jack’s first, appeared before he was twenty.

  3. The eight-month tour that became thirty-five years. Jack, Hedvig, and the two children (Vil 8, Kirsten 5) left for America in July 1939 expecting to return the following spring. They never did, as a family. Thirty-six years later, in 1975, Jack died a US citizen in Santa Monica.

  4. Why UCLA, not MIT. Hedvig told Eliassen that Jack chose UCLA “in order to be near the Scripps Oceanographic Institution in La Jolla; he was of the opinion that cooperation with oceanographers was important” (Eliassen, 1995, p. 12). This was 1940, before the ocean featured in meteorology at all. Two decades before he published the Bjerknes feedback, he had already bet his career on the coupling hypothesis.

  5. The coincidence of 1957. Three scientific fathers – Rossby, Sverdrup, Helland-Hansen – all died in 1957. The same year, the IGY instrumented the tropical Pacific for the first time in history and recorded the great 1957–58 El Niño. Sixty-year-old Jack Bjerknes, the orphan of this Norse-American oceanographic circle, turned to the Pacific and never left.

  6. Walker and Bjerknes never met. Sir Gilbert Walker, the Englishman who discovered the Southern Oscillation in the 1920s, died in 1958 aged 90, just as Jack was starting his Pacific work. The Walker Circulation is a posthumous honorific: Jack named it in 1969, eleven years after Walker’s death. There is no evidence in Jack’s or Walker’s records that they corresponded or met.

  7. The chain reaction, in his own words. In the 1969 paper Jack described the positive feedback in one of the most-quoted sentences in climate dynamics: “This chain reaction shows that an intensifying Walker Circulation also provides for an increase of the east-west temperature contrast that is the cause of the Walker Circulation in the first place.” (Bjerknes, 1969, MWR 97: 163–172, p. 171).

  8. Father and son, eleven years to the day. Germany invaded Norway on 9 April 1940; Vilhelm Bjerknes, Jack’s father, died in Oslo on 9 April 1951 – eleven years to the day after the invasion that had stranded his son in California. Vilhelm’s death is not an anecdote in Jack’s own career, but the coincidence of date is striking.

Primary Sources

  • Eliassen, Arnt. “Jacob Aall Bonnevie Bjerknes, 1897–1975.” Biographical Memoirs of the National Academy of Sciences, Volume 68 (1995). PDF: http://biographicalmemoirs.org/pdfs/bjerknes-jacob-a.pdf – Accessed: 2026-04-24. The primary biographical source; written by Arnt Eliassen with information from Hedvig Bjerknes, Morton Wurtele, and Akio Arakawa.

  • Holmboe, J., Namias, J., and Wurtele, M. G. “Jack Bjerknes, Meteorology: Los Angeles.” University of California In Memoriam, May 1977 (UC Berkeley University Archives). https://texts.cdlib.org/view?docId=hb1199n68c;chunk.id=div00007;doc.view=frames;brand=oac4 – Accessed via Wayback Machine 2021 snapshot, 2026-04-24. Includes the children’s names (Vil b. 1931, Kirsten b. 1934), the 1940 exile story in Hedvig’s words, and the Fjørtoft valediction.

  • Bjerknes, J. (1966). “A possible response of the atmospheric Hadley circulation to equatorial anomalies of ocean temperature.” Tellus 18(4): 820–829. DOI: https://doi.org/10.3402/tellusa.v18i4.9712 . Tellus open-access landing page: https://tellusjournal.org/articles/10.3402/tellusa.v18i4.9712 – Accessed: 2026-04-24.

  • Bjerknes, J. (1969). “Atmospheric teleconnections from the Equatorial Pacific.” Monthly Weather Review 97(3): 163–172. DOI: https://doi.org/10.1175/1520-0493(1969)097%3C0163:ATFTEP%3E2.3.CO;2 . AMS journal page: https://journals.ametsoc.org/view/journals/mwre/97/3/1520-0493_1969_097_0163_atftep_2_3_co_2.xml . Open-access copy: https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/ENSO/Bjerknes-1969.pdf – Accessed: 2026-04-24.

  • Bjerknes, J. (1919). “On the Structure of Moving Cyclones.” Geofysiske Publikasjoner I(2). See Post 3 of the NWP history series.

  • Wurtele, M. G., ed. Selected Papers of Jacob Aall Bonnevie Bjerknes (Western Periodicals Co., North Hollywood, CA, 1975). Reproduces Jack’s full bibliography through 1974.

  • Friedman, Robert Marc. Appropriating the Weather: Vilhelm Bjerknes and the Construction of a Modern Meteorology (Cornell University Press, Ithaca NY, 1989). The standard scholarly history of the Bergen School. Cited by Eliassen (1995) as a key source.

Secondary Sources

  • “Jacob Bjerknes.” Wikipedia. https://en.wikipedia.org/wiki/Jacob_Bjerknes – Accessed: 2026-04-24.
  • “Jacob Bjerknes.” Encyclopaedia Britannica. https://www.britannica.com/biography/Jacob-Bjerknes – Accessed: 2026-04-24.
  • “Bjerknes, Jacob Aall Bonnevie.” Complete Dictionary of Scientific Biography, Encyclopedia.com. https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/bjerknes-jacob-aall-bonnevie – Accessed: 2026-04-24.
  • “Bjerknes: Linking the Southern Oscillation with El Niño.” IRI/LDEO Climate Data Library. https://iridl.ldeo.columbia.edu/maproom/ENSO/New/bjerknes.html – Accessed: 2026-04-24.
  • “Vilhelm and Jacob Bjerknes – How a Father and Son Helped Create Weather Forecasting as We Know It.” CIRA/RAMMB (Colorado State). https://rammb.cira.colostate.edu/dev/hillger/pdf/Vilhelm_and_Jacob_Bjerknes.pdf – Accessed: 2026-04-24.
  • “Jacob Bjerknes Papers.” Niels Bohr Library & Archives, American Institute of Physics. https://history.aip.org/phn/11411003.html – Accessed: 2026-04-24. Archival finding aid; confirms the AIP records but no oral history of Jack himself exists.
  • “History.” UCLA Department of Atmospheric and Oceanic Sciences. https://atmos.ucla.edu/history/ – Accessed: 2026-04-24.
  • “Jacob Bjerknes (1897–1975)” – AGU Jacob Bjerknes Lecture page. https://honors.agu.org/bowie-lectures/bjerknes/ – Accessed: 2026-04-24 (note: AGU site was behind a Cloudflare challenge at research time, but the URL is the canonical record).
  • Edwards, Paul N. A Vast Machine, MIT Press (2010) – UCLA chapter. https://pne.people.si.umich.edu/vastmachine/i.UCLA.html – Accessed: 2026-04-24.
  • “Weather Forecast Pioneer Dies.” Santa Cruz Sentinel (8 July 1975), p. 24 (wire obituary). Via Newspapers.com; cited in the Wikipedia article.
  • “Winners of the IMO Prize.” World Meteorological Organization. Wikipedia citation retrieved 9 December 2015 from the archived WMO page.