The jet stream was not discovered in a single eureka moment but pieced together over roughly two decades, from the 1920s through the early 1940s. A Japanese meteorologist named Wasaburo Oishi made the earliest systematic observations of powerful high-altitude winds near Mount Fuji starting in 1923, but his findings, published largely in Esperanto, went virtually unnoticed outside Japan. It took aviators, wartime bomber crews, and theoretical meteorologists working independently to bring the phenomenon into full scientific view.
Wasaburo Oishi and the Winds Above Mount Fuji
Oishi ran the Tateno Aerological Observatory near Tsukuba, Japan, and beginning in the early 1920s he launched pilot balloons (small, hydrogen-filled balloons tracked by theodolite) to measure wind speed and direction at various altitudes. By carefully following these balloons as they rose through the upper atmosphere, Oishi documented astonishingly fast westerly winds at heights above about nine kilometers. Some of his measurements recorded wind speeds exceeding 200 kilometers per hour at altitudes that commercial aircraft barely reached at the time.
Oishi published his results in a series of reports during the mid-1920s, many written in Esperanto, the constructed international language that a small community of scientists hoped would break down language barriers. In practice, it did the opposite. Western meteorologists largely ignored the reports because few read Esperanto, and the findings did not circulate in the major European or American journals. This meant that Oishi’s careful documentation of what we now call the jet stream remained an obscure footnote for years, even as other people stumbled across the same phenomenon through completely different means.
Wiley Post and the View From the Cockpit
While Oishi was tracking balloons, aviators were beginning to push into the stratosphere. Wiley Post, the American pilot famous for flying solo around the world in 1933, was among the first to encounter jet-stream winds firsthand during his high-altitude test flights in the mid-1930s. Post had developed a pressurized flight suit that allowed him to fly at altitudes above 30,000 feet, far higher than most aircraft of the era. During these flights, he noticed that his ground speed was dramatically different from his airspeed, a clear sign that powerful winds were pushing or resisting his aircraft at high altitude. Post is frequently credited with discovering the jet stream from the cockpit, an encounter born from his push to fly higher and faster than anyone before him.1PubMed. Wiley Post, around the world with no stereopsis
Post’s observations were anecdotal rather than systematic. He was a daredevil aviator, not a meteorologist, and he died in a 1935 plane crash in Alaska before he could formalize his findings. But his experience illustrated something important: the upper atmosphere was not a calm, uniform space. It contained rivers of fast-moving air that could either help or hinder an airplane depending on the direction of travel.
World War II and the Bomber Crews
The jet stream truly entered the awareness of the military and scientific establishment during the Second World War. American B-29 Superfortress crews flying bombing missions over Japan at altitudes above 25,000 feet encountered headwinds so ferocious that their ground speed sometimes slowed to a crawl, despite engines running at full power. Crews reported winds of 200 miles per hour or more blowing directly against their flight path. On some missions, the headwinds were so strong that the bombers could barely make forward progress, and their ability to hit targets plummeted because the wind pushed bombs far off course.
Japanese military meteorologists, meanwhile, had actually exploited their knowledge of these upper-level winds. Between late 1944 and early 1945, Japan launched thousands of incendiary balloon bombs, known as “Fu-Go” weapons, designed to ride the jet stream eastward across the Pacific Ocean to North America. The balloons were crude but clever, using a barometric altimeter to maintain altitude by dropping ballast or venting hydrogen. Several hundred reached North America, causing scattered small fires and a handful of casualties. It was a grim practical demonstration that the high-altitude wind system Oishi had documented two decades earlier was real, powerful, and predictable enough to weaponize.
The wartime experience forced Western meteorology to take high-altitude wind patterns seriously. After the war, research into the structure and behavior of these wind currents accelerated rapidly.
Who Coined the Term “Jet Stream”?
The German meteorologist Heinrich Seilkopf is generally credited with introducing the term “Strahlströmung” in 1939, which translates literally as “jet current” or “jet stream.” The term was adopted into English-language meteorology during and after the war. Some historians have pointed out that other scientists used similar descriptions earlier, but Seilkopf’s coinage is the one that stuck and became standard in scientific literature.
It is worth noting that the naming happened well before the phenomenon was fully understood. Having a name helped consolidate scattered observations from balloon data, pilot reports, and theoretical calculations into a single concept. Before Seilkopf’s term gained traction, different researchers described the same phenomenon in different ways, making it hard to recognize that they were all talking about the same thing.
Rossby Waves and the Theoretical Framework
Understanding why the jet stream exists required theoretical work, and the key figure was Carl-Gustaf Rossby, a Swedish-American meteorologist. Rossby is best known for discovering the large-scale planetary waves in the atmosphere that now bear his name, and he is considered one of the most influential meteorologists of the twentieth century.2Physics Today. Carl-Gustaf Rossby: Theorist, institution builder, bon vivant In the late 1930s and 1940s, Rossby developed mathematical descriptions of how the rotation of the Earth and the temperature difference between the equator and the poles combine to create large undulating waves in the upper-level wind flow. These waves, in turn, shape where the jet stream sits and how it meanders.
Rossby’s framework transformed the jet stream from a curiosity that pilots occasionally bumped into to a central organizing feature of mid-latitude weather. His work showed that the jet stream was not random but followed from basic physics: the planet’s rotation, the uneven heating of the surface, and the conservation of angular momentum. This theoretical backbone made it possible to predict the jet stream’s behavior and, eventually, to use it in weather forecasting.
What Jet Streams Actually Are
A jet stream is a narrow band of fast-moving air in the upper troposphere, typically between about 7 and 12 kilometers above the surface. Wind speeds within a jet stream core commonly range from 100 to over 300 kilometers per hour, far faster than the surrounding air. The bands are relatively narrow, often only a few hundred kilometers wide and a couple of kilometers deep, but they stretch for thousands of kilometers around the planet.
Two main jet streams exist in each hemisphere. The subtropical jet sits near 30 degrees latitude and is driven largely by the Hadley circulation, the large convective loop that carries warm air from the tropics poleward. The polar-front jet (or polar jet) forms near 50 to 60 degrees latitude along the boundary between cold polar air and warmer mid-latitude air. In addition to these permanent features, temporary jet streams appear under certain conditions, including the Tropical Easterly Jet over Africa and South Asia and low-level jets found closer to the surface.3ResearchGate / Agri Mirror: Future India. Jet streams- A Conceptual Review
The polar jet is the one most people hear about in weather forecasts, because it is the one that steers mid-latitude storm systems. When the polar jet dips southward, it pulls cold air with it, producing cold snaps. When it swings northward, warm air floods poleward. The position and waviness of the polar jet essentially determine much of the day-to-day weather across North America, Europe, and northern Asia.
How Airlines Use and Avoid the Jet Stream
Commercial aviation learned to work with the jet stream almost as soon as the phenomenon was understood. Flying eastbound, pilots seek out jet-stream tailwinds that can shave an hour or more off a transatlantic or transpacific flight and save significant fuel. Flying westbound, they route around the jet stream to avoid punishing headwinds. This asymmetry means that eastbound flights between, say, New York and London are consistently shorter than the return trip.
The tradeoff is turbulence. The jet stream’s edges, where fast-moving air meets slower surrounding air, generate clear-air turbulence that cannot be seen on radar. A recent study of transatlantic routes found that eastbound flight paths, which fly closer to the jet stream to exploit tailwinds, encounter roughly 60 percent more moderate-or-greater clear-air turbulence than westbound routes that steer away from it.4Nature. Combined impact of jet stream and turbulence on long-term trans-oceanic flight routes over North Atlantic Ocean using ERA5 reanalysis Pilots and dispatchers must constantly balance the fuel savings of a tailwind against the bumpiness and safety considerations of flying near the turbulent core.
Modern flight planning software integrates real-time jet-stream data to optimize routes on every individual flight, adjusting altitude and lateral position to find the best compromise between speed, fuel burn, and passenger comfort. This is a direct descendant of what Wiley Post and those B-29 crews discovered by brute experience: the upper atmosphere is not a uniform environment, and the jet stream can be either your best friend or your worst enemy depending on which direction you are heading.
Shifting Jet Streams in a Warming World
One of the more actively debated questions in climate science is how the jet stream is responding to rising global temperatures. Observations over recent decades show that, broadly, jet streams in both hemispheres have shifted poleward and risen in altitude. In the Northern Hemisphere, the jet has weakened overall, while in the Southern Hemisphere, the subtropical jet has weakened but the polar jet has strengthened.5CrossRef API / Geophysical Research Letters. Historical trends in the jet streams
The mechanism researchers focus on most is called Arctic amplification: the Arctic has warmed at roughly twice the rate of the mid-latitudes since the 1990s, shrinking the temperature difference between the pole and the equator. Because that temperature gradient is what drives the polar jet, a weaker gradient should mean a weaker, more meandering jet stream. Research has found evidence supporting this connection, showing that the Northern Hemisphere’s upper-level circulation has indeed taken on a “wavier” character, with larger north-south swings in the jet’s path occurring more frequently.6PubMed Central. Evidence linking rapid Arctic warming to mid-latitude weather patterns
A wavier jet stream is not just a matter of academic interest. When the jet takes larger, slower-moving meanders, weather systems tend to stall. A stalled ridge can produce prolonged heat waves; a stalled trough can deliver extended cold spells or relentless rainfall. The hypothesis, supported by a growing body of evidence, is that continued Arctic warming will produce an increasingly wavy jet stream and, with it, more persistent extreme weather events.7Environmental Research Letters. Evidence for a wavier jet stream in response to rapid Arctic warming This remains one of the most consequential open questions in climate science, because it links greenhouse gas emissions not just to gradual warming but to the kinds of intense, week-long weather events that do the most damage to agriculture, infrastructure, and human life.
Jet Streams Beyond Earth
Earth is not the only planet with jet streams. The gas giants Jupiter and Saturn have extraordinarily powerful jet streams visible as the colored bands that stripe their atmospheres. Jupiter’s banded appearance is essentially a map of alternating eastward and westward jet streams, some blowing at hundreds of meters per second. Saturn’s jet streams are equally dramatic, and the Cassini spacecraft provided detailed observations of their structure, seasonal changes, and associated storm systems during its 13-year mission in the Saturnian system.8PubMed Central. Cassini Exploration of the Planet Saturn: A Comprehensive Review
The basic physics is the same: planetary rotation combined with uneven heating creates organized bands of fast-moving air. But the details differ enormously. Jupiter and Saturn lack solid surfaces, so their jet streams extend deep into the atmosphere rather than hugging a boundary layer. The speeds involved dwarf anything on Earth. Saturn’s equatorial jet can exceed 400 meters per second, roughly four times the fastest winds recorded in Earth’s jet stream. Studying these alien jet streams helps meteorologists test and refine the theoretical models that also apply to Earth, because each planet represents a natural experiment with different rotation rates, compositions, and energy inputs.
Why Discovery Credit Is Complicated
Ask “who discovered the jet stream” and you will get a different answer depending on who you ask and what counts as discovery. Oishi made the first systematic measurements in the 1920s but did not reach an international audience. Post physically encountered jet-stream winds in the 1930s but was an aviator, not a scientist, and left no formal record of the discovery. Seilkopf gave the phenomenon its name in 1939. B-29 crews and Japanese balloon engineers proved its military significance in the 1940s. Rossby explained why it exists.
This kind of distributed discovery is common in atmospheric science. The atmosphere does not reveal its secrets to a single observer in a single place. It took people on different continents, working with different tools and different goals, to accumulate enough evidence to say, “There is a persistent river of fast wind high in the atmosphere, it circles the planet, and it matters.” The discovery of the jet stream is less a date on a timeline than a slow accumulation of observations, encounters, and theory stretching over about 20 years. If forced to pick a single starting point, most meteorological historians point to Oishi’s balloon observations beginning around 1923, but the full picture did not snap into focus until the 1940s, when wartime aviation, Rossby’s theoretical work, and improved upper-air observation networks all converged.