## How does this simulation work?

The NWS is built using Unity3D and is a stand-alone application which must be downloaded. Because of the large data-sets, the size of the software is several GBs. The effects of nuclear weapons are calculated on the CPU for interaction with objects and on the GPU for interaction with the high-density population grid. Surface shaders are used to visualise data like population density and radiation dose from fallout.

## Models used to calculate nuclear weapons effects

Overpressure is calculated using the Brode-Equation provided by Edward Geist https://github.com/GOFAI/glasstone

Thermal radiation is calculated by digitizing the model in Samuel Glasstone and Philip J. Dolan “The effects of nuclear weapons”, Third Edition 1977.

Fallout is calculated using the WSEG10 model provided by Edward Geist https://github.com/GOFAI/glasstone

Prompt radiation is not calculated but will be added in the future.

Height of burst at which fallout occurs is calculated using the equation from Samuel Glasstone and Philip J. Dolan “The effects of nuclear weapons”, Third Edition 1977.

Relative flash intensity and peak time are calculated from yield using the equations from Samuel Glasstone and Philip J. Dolan “The effects of nuclear weapons”, Third Edition 1977.

Conditions for mass fires are determined as a threshold of thermal radiation and population density with the Binninger model and values from “Nuclear war between Israel and Iran” by Dallas et al. 2013. Based on data from World War II, the fuel density threshold for mass fires is usually assumed to be 8 pounds fuel per square foot, which corresponds to a population density of 3550 /km^2 if we use the data in “Rapidly expanding nuclear arsenals in Pakistan and India portend regional and global catastrophe” by Brian Toon et al. Science Advances 02 Oct 2019.

Soot calculation is adapted from Brian Toon, Alan Robock and Rich Turco “Environmental consequences of nuclear war” 2008. The results are not very well tested and the calculation of expected cooling is very simple. This model must be tested and improved in the future.

## Calculation of casualties

The effects mentioned above are calculated for each population density cell and adjustable fatality rate curves are used to calculate the casualties.

The fatality rate curves for overpressure, thermal radiation and cumulative fallout radiation dose are shown in the figure above. These curves can be adjusted if the user thinks they are too optimistic or too pessimistic.

The overpressure curve is an approximation of the DOD calculations. The curve is not continuous and is probably not the most realistic one, but it seems to be the most widely used model for this calculation.

The thermal radiation curves are digitized from John S. Duffield and Frank von Hippe ” The Short-term Consequences of Nuclear War for Civilians ” 1984. The curves are depending on the yield of the weapon because larger weapons have longer thermal pulse duration. The individual curves were adjusted using the probability for burns at different yields in Samuel Glasstone and Philip J. Dolan “The effects of nuclear weapons”, Third Edition 1977.

The fallout curve is adapted from Joseph Rotblat “Acute Radiation Mortality in a Nuclear War” 1986.

## Databases

Population density is imported from the GHSL Data Package 2019 https://ec.europa.eu/jrc/en/publication/ghsl-data-package-2019.

Pesaresi, Martino; Florczyk, Aneta; Schiavina, Marcello; Melchiorri, Michele; Maffenini, Luca (2019): GHS

settlement grid, updated and refined REGIO model 2014 in application to GHS-BUILT R2018A and GHS-POP

R2019A, multitemporal (1975-1990-2000-2015), R2019A. European Commission, Joint Research Centre (JRC)

[Dataset] doi:10.2905/42E8BE89-54FF-464E-BE7B-BF9E64DA5218 PID: http://data.europa.eu/89h/42e8be89-

54ff-464e-be7b-bf9e64da5218

CCMP vector winds are produced by Remote Sensing Systems and sponsored by NASA. Data are available at www.remss.com