HYSPLIT Nuclear Applications and Emergence Responses

The creation of the Air Resources Laboratory (ARL) was associated with its task of finding the location of the first Soviet Union atomic test site through back trajectory calculation. Although the HYSPLIT model has been gradually developed, improved, and implemented in various applications at ARL, the predictions of radionuclides’ transport, dispersion, and deposition remain an important part of the ARL’s research and operation support activities due to their significant impact to human health. ARL together with NOAA National weather Service (NWS) National Centers for Environmental Predication (NCEP), designated by the World Meteorological Organization (WMO) as the Washington Regional Specialized Meteorological Centre (RSMC), has been performing routine monthly forecast exercises for potential nuclear power plant accidents and other nuclear incidents with other RSMC partners and the International Atomic Energy Agency (IAEA) since 1993. Another operational product created at ARL is a HYSPLIT-based software for on-demand backtracking support to the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). It has been operational at the NCEP Central Operations (NCO) since 2014 and reliably provides the CTBTO with HYSPLIT backward dispersion products within 24 hours upon request multiple times a year. While dealing with the Fukushima nuclear accident in 2011, the ARL scientists designed a transfer coefficient matrix (TCM) approach in order to update the model predictions more efficiently. In this approach, the TCMs in combination with frequently updated emission scenarios as well as radionuclide decay are post-processed to generate corresponding predictions without rerunning the models. Adopting the TCM approach, ARL scientists also developed an inverse HYSPLIT modeling system to estimate the Fukushima Cs-137 emission temporal profile using the air concentration measurements from the CTBTO International Monitoring System (IMS) and other surface stations. Currently ARL scientists have been building a HYSPLIT forecasting system using the TCM approach for potential nuclear accidents and leading the effort to help other RSMCs to have similar TCM forecasting systems in the future. In the meantime, ARL scientists have been actively involved in many collaborating efforts with other national agencies and laboratories in different nuclear applications and participated in several international nuclear atmospheric transport modeling studies.