Sunday 26 April marks the anniversary of the Chernobyl nuclear accident, one of the most significant environmental events of the 20th century.
While the explosion itself happened far beyond the UK’s borders, its impacts were felt across much of Europe, including the British Isles. Importantly, Chernobyl fundamentally changed how atmospheric dispersion of hazardous material is understood, modelled and communicated, acting as a catalyst for the development of tools still being advanced and relied upon today.
The Chernobyl incident
On 26 April 1986, a catastrophic explosion occurred at Reactor 4 of the Chernobyl Nuclear Power Plant in what is now northern Ukraine. In the days that followed, large quantities of radioactive material were released into the atmosphere and transported across Europe by the wind. Initially, little information was shared internationally. Radioactive material was detected in Scandinavia and later the scale of the incident became clear.
As the radioactive plume spread further west, meteorologists began analysing where and when it might reach different countries, including the UK. Rainfall was of particular concern, as it could enhance the deposition of radioactive material at the surface. These early dispersion assessments highlighted both the importance and the challenges of predicting how hazardous material spreads through the atmosphere.
The need for advanced dispersion modelling
The Chernobyl accident exposed limitations in the tools available at the time to model atmospheric dispersion over long distances and extended periods. Existing approaches struggled to represent complex, evolving meteorological conditions and the physical processes affecting airborne material, such as turbulence, rainfall and surface interactions.
In response, it was agreed that the Met Office would take the lead in developing a more advanced modelling capability to support decision-making during future nuclear or environmental emergencies with releases to the atmosphere. The goal was to create a system capable of simulating how hazardous material moves, transforms and is removed from the atmosphere, from local to global scales.
This work led to the development of the Numerical Atmospheric-Dispersion Modelling Environment, commonly known as NAME.
What is the NAME model?
NAME is a sophisticated atmospheric dispersion modelling system designed to simulate the transport and fate of airborne material. Rather than focusing solely on one type of incident, it was built to be flexible, allowing it to be continually improved and applied across a wide range of atmospheric dispersion scenarios.
At its core, NAME can model how gases and particles are carried by winds, mixed by atmospheric turbulence, transformed through chemistry and removed through processes such as rainfall or surface deposition. NAME can represent a range of gas and particle properties, allowing it to be used for a wide range of substances from radioactive material to volcanic ash, chemical pollutants or fungal spores. This makes it a powerful tool for understanding both short-term hazards and longer-term environmental impacts.
How NAME works
One of NAME’s key strengths is its use of a Lagrangian particle approach. In simple terms, the model represents pollutants as thousands to millions of individual particles that move through a simulated atmosphere. Each particle follows the evolving wind field while also experiencing random motion to represent atmospheric turbulence. This avoids making assumptions about the eventual shape or spread of a pollution plume.
Alongside this, NAME also includes an Eulerian framework, better suited to smoothly varying pollutants such as ozone and other species that play a role in air quality prediction. By combining Lagrangian and Eulerian approaches, the system balances detail and efficiency across different applications.
READ MORE: Check out the Met Office archive's Google Arts and Culture page on the Chernobyl disaster
From emergency response to everyday forecasting
Although born from the need to respond to nuclear incidents, NAME’s use quickly expanded. It has continued to be developed and is applied to volcanic eruptions, including large ash clouds that affect aviation, as well as industrial fires, chemical releases and airborne animal and plant diseases.
NAME also plays a vital role in pollen forecasting, helping to predict pollen levels days in advance and the use of NAME for routine air quality forecasting is under development. NAME is used as part of the inversion system to estimate properties of pollution sources (amount released, release locations) by optimising the agreement between NAME’s predictions and measurements of pollutants. In this way it has been used to estimate volcanic emissions and emissions of greenhouse gases and ozone depleting substances, with the latter supporting climate research and international reporting obligations.
By using both forecast and historical meteorological data, NAME can simulate dispersion over timescales ranging from minutes to weeks, and over distances from a few kilometres to the entire globe.
Forecasting impacts for decision making
In emergency response NAME is used to predict the spread of potentially hazardous material. Transforming this into actionable information is essential to mitigate the hazard. Working with experts in government agencies, universities and other organisations, the impacts, such as radioactive dose to humans, air concentration of volcanic ash that can damage aircraft or pollen levels on an easy-to-understand scale turns NAME forecasts into information that can be used to help keep people safe and reduce impacts.
A lasting scientific legacy
The legacy of Chernobyl extends far beyond the immediate impacts of the accident. It played a role in advancing how atmospheric dispersion is approached, placing robust science and clear communication at the heart of environmental protection.
Today, the NAME model stands as an enduring outcomes of those lessons learned. While it was developed in response to a specific crisis, it now underpins a wide range of activities that help protect people, infrastructure and the environment — ensuring that, when the atmosphere carries hazards, we are far better prepared to understand the potential impacts and respond.
NAME is not only used at the Met Office but is used by many external organisations in the UK and internationally, e.g. universities, government agencies, commercial, and other meteorological services. The NAME User Workshop is held annually to exchange ideas and advance collective knowledge of the science, prediction accuracy and application of atmospheric dispersion modelling.
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From the Met Office archive: Map showing estimated spread of radioactive contamination from Chernobyl