Research team develops EPICC air quality model for complex pollution problems

A large Chinese research team has developed an air quality model called EPICC (Emission and atmospheric Processes Integrated and Coupled Community Model) that demonstrates improved accuracy in its representations of ozone and particulate matter with a diameter of 2.5 micrometers or less.

The working group's paper is published in the journal Advances in Atmospheric Sciences on December 20, 2025. This article also introduced a new way of collaboration, where the research is credited to a "working group" as a whole instead of individual researchers.

For a long time, the development of air quality models in China has been done by individual researchers or small teams. This way of working has limited overall progress. The researchers created the "EPICC Model Working Group" credit system for the EPICC project, aiming to solve this collaboration problem. This establishes a new model of open source, shared, and cooperative development, providing a system that allows multiple teams to work together efficiently. The successful development of the EPICC model version 1.0 was a collaborative effort by a Model Working Group consisting of 59 researchers from 13 institutions, including the Institute of Atmospheric Physics (Chinese Academy of Sciences), Tsinghua University, and Peking University.

“The development and open-source sharing of this model is a key step for China, moving from following international leaders to running alongside them and even taking the lead in this field. More than just a scientific tool, the working group model offers a ‘China solution’ that other research areas around the world facing similar collaboration challenges can learn from,” explains the EPICC Model Working Group.

The EPICC model is a 3D tropospheric chemistry transport model. Scientists use tropospheric chemistry transport models to study how air pollution and gases move about in the lower atmosphere. These models help scientists better understand pollution and climate change. They are essential scientific tools for pollution control, using numerical simulations to show how pollutants form, move, and settle.

Because of its rapid socioeconomic develop and urbanization, China has become one of the most polluted regions in the world. The presence of coal smoke pollution, acid deposition, photochemical smog, and haze weather all impact China today.

The tropospheric chemistry transport models were first developed in the 1970s. These models have undergone many changes since that time. Today, the models are used to demonstrate differing levels of simulation capability and each is endowed with unique strengths. “Currently, the leading international models are mostly developed in the United States. While these laid the foundation for the field, they aren't always a perfect fit for the complex air pollution characteristics found in China,” explains the EPICC Model Working Group. Scientists in China have realized that creating an open-source model framework is the most efficient approach to enhancing simulation capabilities. 

In 2017, the National Key Scientific and Technological Infrastructure project “Earth System Numerical Simulation Facility” (Earth-Lab) in China was launched. This project provided a regional high-precision simulation system for air pollution, aimed to greatly enhance current levels of high-resolution simulation technology and capacity. It catered to scientific research and application needs focused on the regional environment. In 2021, the National Natural Science Foundation of China funded the “Integrated Research on Simulation, Forecast, and Prediction of the Air Pollution Complex in China.” This project, together with EarthLab, developed the Emission and Atmospheric Processes Integrated and Coupled Community (EPICC) model version 1.0. The EPICC model integrated recent achievements in key physical and chemical processes from the joint major research program called “Formation Mechanisms, Health Effects, and Mitigation Strategies of Air Pollution Complex in China.” 

The EPICC model uses a scientific, modular structure with a standard version control system and a "plug-and-play" design. It includes key physical and chemical processes, such as manganese-catalyzed sulfate chemistry, multiple ways nitrous acid is formed, and interactions between aerosols, clouds, and sunlight. Performance tests show that the EPICC model significantly improves the accuracy of simulating PM₂.₅ (particular matter with a diameter of 2.5 micrometers or smaller) and ozone. It effectively fixes issues found in traditional models, which often underestimated sulfate levels and overestimated summer ozone levels.

The EPICC Model Working Group hopes this model can be useful in regions beyond China. “This model can provide a more effective decision-making tool for China and other rapidly developing countries facing similar complex air pollution problems,” they say.

The EPICC model source code and standard input files can be downloaded from The Earth System Science Numerical Simulator Facility Community Data Portal (https://earthlab.iap.ac.cn/en/index.html).

The research is funded by the National Natural Science Foundation of China and the National Key Research Development Program of China.