11:15 AM - 11:30 AM
[HCG22-09] Discovery and Analysis of Meteorological Recording Charts from the Time of the 1945 Hiroshima Atomic Bombing
Keywords:Hiroshima, Atmoc Bomb, Meteorological Observation
Newly discovered meteorological recording charts from the 1945 Hiroshima atomic bombing provide the only known continuous meteorological data from that period. Observations were conducted at the present-day Hiroshima Ebayama Meteorological Museum (30 m a.s.l.), 2.7 km south-southwest (SSW) of the hypocenter. Despite blast and heat effects, the building remained intact, preserving meteorological instruments.
Previously, Hiroshima Meteorological Observatory compiled handwritten records, the "Monthly Report of Hourly Meteorological Observation in Hiroshima," available online. We have used these to validate black rain simulation models.
Recording charts were exchanged at 9:00 AM, so data for temperature, humidity, pressure, and wind speed exist before and after this time on August 6. Wind direction data is incomplete, but traces indicate north to northwest winds between 8:00–9:00 AM.
No precipitation was recorded on August 5–6, so precipitation charts were not preserved. The barometer recorded a slight pressure rise around 8:15–16 AM, followed by a blank section and a note: "blast wave 8h18m." A 0.7 mmHg pressure drop after 9:00 AM remains unexplained.
The August 5–6 humidity chart is missing, but weekly charts were found, providing valuable continuous records. We have scanned these charts and plan to release numerical data after instrument corrections and comparison with surrounding stations.
Previously, Hiroshima Meteorological Observatory compiled handwritten records, the "Monthly Report of Hourly Meteorological Observation in Hiroshima," available online. We have used these to validate black rain simulation models.
Recording charts were exchanged at 9:00 AM, so data for temperature, humidity, pressure, and wind speed exist before and after this time on August 6. Wind direction data is incomplete, but traces indicate north to northwest winds between 8:00–9:00 AM.
No precipitation was recorded on August 5–6, so precipitation charts were not preserved. The barometer recorded a slight pressure rise around 8:15–16 AM, followed by a blank section and a note: "blast wave 8h18m." A 0.7 mmHg pressure drop after 9:00 AM remains unexplained.
The August 5–6 humidity chart is missing, but weekly charts were found, providing valuable continuous records. We have scanned these charts and plan to release numerical data after instrument corrections and comparison with surrounding stations.