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International meeting
1. Initial conditions
2. Validation data
3. Sources and structure
4. Appendix
5. Related data
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Updated HiSoF's member list.


Updated HiSoF's member list.


HiSoF Book 2 launched, with resent research results and data

Hiroshima City and HiSoF launched the second volume of "Revisit The Hiroshima A-bomb with a Database -Latest Scientific View on Local Fallout and Black Rain-" on March 22, in Hiroshima (see Publications page).

This book contains recently found data and research results by HiSoF members and its collaborators (see Database page), including:

- the wind data based on the navigation record of the aircraft of bomber and two weather stations data in Japan between July and August 1945;

- results of neutron activation analysis of the soils used under roof tiles in traditional Japanese houses, and ground soil samples in Hiroshima city;

- particle size distribution of the soils used for walls and under roof tiles in traditional Japanese houses and ground soil samples;

- a study that suggests the region west to the hypocenter has a higher risk compared to other areas that cannot be explained by direct exposure only;

- measurements of Cesium-137 and Pu isotopes in under-floor soil samples from houses built 1–4 years after 1945 in Hiroshima;

- a paper which asks a question of whether observed Hiroshima TLD excess dose could be the result of a pattern of local fallout of Hiroshima A-bomb.

Books are available from Hiroshima City
HiSoF Book 1 and Book 2 as well as abridged editions in Japanese are available on request. Those wishing to obtain HiSoF publications, please contact Hiroshima City (see Contact).


HiSoF international meeting suspended, while continuing study

First, Hiroshima City and HiSoF would like to express our gratitude to those kindly responded our call for help in finding meteorological observation data on/around the day of the Hiroshima A-bombing. For those data so far obtained by HiSoF, please see Databases page of our website.

International meeting to be pending
However, to conduct international inter-laboratory comparison study of model simulations on local fallout and ‘black rain’, we should regard those meteorological data so far collected are still insufficient to conduct model simulations, especially those on wind field.

We have also examined possibility of using existing wind field obtained by the 20th Century Reanalysis conducted by the NOAA, USA, as the wind field on August 1945. We found there are some discrepancies between observed upper wind data we have now and the wind data in the 20th Century Reanalysis.

Therefore, regarding planned international comparison study on model simulations, Hiroshima City and HiSoF decided that holding meeting in fiscal year of 2013 should be difficult; for the moment, it would be more realistic to suspend the decision on it, while continuing to deepen our study and explore scientific knowledge and data so as to elucidate uncertainties about local fallout and ‘black rain’.

Still seeking meteorological data and information
Hiroshima City and HiSoF are still seeking meteorological data on/around the very day of Hiroshima A-bombing. Your help and collaboration in finding those data would be enormously appreciated. For details, please refer to HiSoF news dated on May 29, 2012.

HiSoF book Vol.2
HiSoF is currently preparing the book two, which contains additional data and results of our latest study since last publication, Revisit The Hiroshima A-Bomb with a Database, in July 2011. The second volume of HiSoF book will be issued by Hiroshima City before the end of March 2013.

Help us with upper-air wind data !

The major objective of the HiSoF project is to illustrate a more realistic picture of radioactive fallout and 'black rain' due to the Hiroshima atomic bombing on 6th August 1945. Hiroshima City and HiSoF are planning to perform numerical model simulation on this aspect, and have been preparing the database regarding with heat and water fluxes and radioactivity filed for this purpose.

Most of data necessary for model simulation is basically prepared. However those of wind field, crucial to determine the movement of mushroom cloud which might regulated range of 'black rain', is still missing. Actually one of the major controversies over 'black rain' is how to identify the affected area. Scarcity of meteorological data during the wartime and its aftermath hinders drawing of an accurate map of the area where experienced 'black rain'.

In an attempt to re-construct the meteorological field of Hiroshima on Aug.6, 1945, HiSoF explored historical weather observation records kept at the central and local meteorological observatories in Japan as well as the National Archives of the United States

We first pursued the weather record of the very day of the atomic bombing, including those measured by the US weather squadrons. One of our findings is listed in the HiSoF Database (see Section 5. Related data). However the record of this specific date and location could be barely available, we therefore expanded the range of the target.

Unfortunately, meteorological data necessary for conducting model simulation is still insufficient. We thus would like to ask your collaboration to obtain upper-air wind data with a following scope.

-- Range of area
Latitude: from 25 deg. N to 40 deg. N
Longitude: from 110 deg. E to 140 deg. E
Altitude: Surface to 18000 m
(namely Japan, North East China, Korean Peninsula, Taiwan, Russian Far East, Pacific)

-- Time period
Any day(s) from July 20 through Aug. 15, 1945

-- Parameters
Wind direction, wind speed, air temperature, humidity

A tentative deadline to submit information is 31st August 2012.

Many appreciations for your collaboration!

To submit information, and to obtain more details, please contact;


c/o Research Division, Atomic Bomb Survivors Relief Department
Health and Welfare Bureau, Hiroshima City Hall, 1-6-34 Kokutaiji-machi,
Naka-Ku, Hiroshima, JAPAN 730-858


Overview and outlook of HiSoF activities

HiSoF has been carrying in-depth research and analysis on local fallout and "black rain" from the A-bomb explosion at Hiroshima on 6 August 1945. The main purpose of our studies is to create a database for conducting numerical model simulation on distribution of radioactive fallout and "black rain".

Our analysis and findings so far were compiled into the HiSoF database (see Datebase). The database includes initial conditions and boundary conditions for numerical model simulation such as distribution of fission products in the mushroom cloud, heat, water and carbon fluxes from surface of the ground and so on.

HiSoF summarized on our studies up to the autumn of 2011 as that we should regard most of data necessary for model simulation, except those on wind field, are basically prepared. Regarding wind field, it still requires a further research and examination. HiSoF shall continue exploring documents and information on this aspect over the year 2012, as well as developing more comprehensive database on other fields.

With coming new findings and analysis, we are planning to publish HiSoF Book Vol.2. Then judging from the progress in our studies, Hiroshima City and HiSoF shall consider the possibility of holding the international meeting on the inter-laboratory comparison of model simulations in the year 2013. The latest news on HiSoF activities will be announced in our website.


Record of update
Launch : 2010-11-25
Update : 2016-12-15


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