Study Estimates Hiroshima Firestorm Plume Above 11 Km
Researchers used a 1945 flight log entry and simulations to estimate the height of the smoke cloud over Hiroshima.
Updated on Nov. 4, 2026 in Severe Weather
A study led by atmospheric scientist David Romps of the University of California, Berkeley, estimates the smoke plume from the Hiroshima firestorm on August 6, 1945 exceeded 11.3 kilometres in height. The analysis was published in Geophysical Research Letters on October 28.
Why it matters
The estimate relies on navigator Theodore Van Kirk's flight log entry 'CLOUD GONE,' written 97 minutes after the bombing, which the researchers used as a physical observation constraint. Quantifying the plume's height helps characterize how smoke from large urban fires can reach the upper atmosphere.
The estimate rests on a flight log entry recorded 97 minutes after the bombing, from an aircraft roughly 750 to 764 kilometres away at about 7,440 metres. Researchers ran 100,000 simulations to account for uncertainties in position, altitude and weather, yielding a minimum plume height above 11.3 kilometres at 95 per cent confidence.
The players
David Romps
An atmospheric scientist at the University of California, Berkeley, who led the study estimating the height of the Hiroshima firestorm plume.
Theodore Van Kirk
The navigator aboard the Enola Gay whose 1945 flight log entry 'CLOUD GONE' was used as evidence in the plume analysis.
The details
Researchers examined the aircraft's recorded position, altitude and historical atmospheric conditions, and their calculations accounted for how light bends through the atmosphere. A military memorandum noted the crew's observation was limited by haze rather than the curvature of the earth.
Timeline
August 6, 1945, 8:15 am local time: Enola Gay dropped the atomic bomb Little Boy on Hiroshima.
August 6, 1945, 10:52 am Tinian time: Navigator recorded 'CLOUD GONE' in the flight log.
October 28, 2026: The firestorm plume study was published in Geophysical Research Letters.
Seasonal Patterns
The study extends the historical record of the 1945 Hiroshima bombing by quantifying the firestorm smoke plume, which had not been precisely characterized before. The estimate offers a physical benchmark for how large urban fires can loft smoke into the upper atmosphere.
The study is a historical reconstruction and does not describe a current hazard. Readers researching the Hiroshima bombing can consult the peer-reviewed findings in Geophysical Research Letters for the full methodology and uncertainty analysis.
The takeaway
Historical records such as a single flight log entry can be combined with atmospheric modeling to reconstruct physical effects of past events. The method shows how uncertainty can be bounded even when direct measurements were never taken.
Further reading
For related context on extreme atmospheric events, explore Severe Weather coverage.
Source note: This article includes information reported by Hindustan Times.
