Real time simulations of nuclear cloud rise with the energy research and forecasting model

Operational models of nuclear cloud rise are required to have short simulation times to facilitate timely response by decision makers and emergency personnel. Because of this, current models are low dimensional approximations and rely on parameterized variables tuned to historical U.S. nuclear test results. These simplifications limit the capacity of current models to account for complex interactions with the local environment. As an alternative, this study examines the use of a new multiscale atmospheric solver, the Energy Research and Forecasting model (ERF), for use in fallout modeling applications. By simulating the fully three dimensional and time varying atmosphere dynamics, including turbulence with large eddy simulation (LES), significantly fewer modeling assumptions are required. In this study, four historical U.S. nuclear tests with varying heights of burst were simulated in ERF using an idealized setup and the results agree favorably with both historical test data and previous simulation data from the Weather Research and Forecasting model (WRF). Furthermore, it was demonstrated that cloud rise simulations could be performed faster than real time by leveraging GPU accelerated high performance computing resources with a combination of adaptive time stepping and adaptive mesh refinement. This represents a significant improvement in capability for nuclear cloud rise simulations and may enable the use of ERF as an operational tool in emergency situations.