A demonstration of CTBTO’s capability to identify the possible source region of the specific case of DPRK announced tests by conducting a sensitivity study using high-resolution ATM

Detection of radionuclides released from a nuclear explosion is an essential task mandated by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Atmospheric transport modelling (ATM) identifies either possible source regions for relevant radionuclide observations at anomalous concentrations through the so-called International Monitoring System (IMS) or potential stations for measuring releases from known source locations. This is a well-known methodology for connecting sources and receptors of any substance in the atmosphere. The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) currently investigates the potential advantages of using high-resolution ATM. Past announced underground nuclear tests at the Punggye-ri Nuclear Test Site from the Democratic People’s Republic of Korea (DPRK) are used in this study to scale the CTBTO’s capability to identify IMS stations that might detect a hypothetical release. These events are also used to identify the capability to locate Punggye-ri as the possible source location.

A sensitivity study is presented that demonstrates the CTBTO’s capability to identify Punggye-ri as a possible source region for the relevant radionuclide measurements at IMS stations. The aim is to find the best model set-up from varying combinations of meteorological resolution, regional domain set-up, and physical parameterization. Variations in resolution are accomplished by using first the Lagrangian Particle Dispersion Model FLEXPART, which will be driven by meteorological fields from the European Centre for Medium-Range Weather Forecast (ECMWF) with either 0.5° or 0.1° spatial and 1 h temporal resolution; and second, by using a combination of the Weather Research and Forecasting Model (WRF) and FLEXPART-WRF to scale down to 1 km spatial resolution. The potential accuracy increase is evaluated by using metrics from previous ATM challenges.