Atmospheric Chemical Mechanism Development

Chemical mechanisms are at the heart of atmospheric chemistry models, representing the complex reactions occurring in the atmosphere. The accuracy of model predictions depends significantly on how well these mechanisms approximate real atmospheric processes. As our scientific understanding evolves, it is crucial to update these mechanisms continuously.

One of our key efforts is the development of a new chemical mechanism called MOZART-TS3, designed to improve the representation of alkane chemistry, which has been simplified in existing mechanisms like MOZART-TS1 and MOZART-TS2. MOZART-TS3 introduces 149 kinetic and 21 photolysis reactions, covering a broader spectrum of chemical processes. These include the initial reactions of alkanes with OH, interactions of peroxy radicals with NO, HO₂, and NO₃, permutation reactions among peroxy radicals, alkoxy radical decomposition, hydrogen shifts, and more. To achieve this, we have been collaborating closely with experts in chemical reactions and the organic gas measurement team.

Multi-Scale
Earth System Modeling

Simulations of the Earth and its atmosphere typically use either global or regional models. While global models often lack the resolution to capture nonlinear processes accurately, regional models address this with finer horizontal resolution. However, they rely on boundary conditions from global models, which can introduce inconsistencies due to differences in chemistry, speciation, emissions, and more. Additionally, maintaining consistent simulations for long-lived species across regional domain boundaries remains challenging.

The Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA) will become a computationally feasible global modeling framework that allows for the simulation of large-scale atmospheric phenomena while still resolving chemistry at emission and exposure-relevant scales (down to ~1 km within the next 5 years). Currently, MUSICA (version 0) is available as a configuration of CAM-chem, the Community Atmosphere Model with Chemistry, which is a component of the Community Earth System Model (CESM). We developed a custom MUSICA grid to simulate Korea at a ~7 km resolution, while simultaneously simulating the globe at a ~100 km resolution. This approach enables capturing small urban areas in South Korea and allows for seamless two-way feedback between Korea and the global scale processes. Additionally, it closely aligns with the GEMS satellite pixel resolution of 7 km × 7.7 km over Seoul, facilitating the integration of satellite observations with the modeling framework.

Climate and Health Impact Assessment

While it is clear that reducing air pollutants is beneficial for human health, the risk models used to estimate health effects still have a lot of limitations and uncertainties. Furthermore, some air quality improvement measures could lead to disbenefits for near-term climate change. The full extent of these trade-offs when integrating air quality and climate change mitigation policies has not yet been fully addressed. On the other hand, aerosols, unlike long-lived greenhouse gases, are unevenly distributed, which means their health and climate effects are strongly influenced by the location of their sources, chemical transformations, and loss processes.
These interactions are bidirectional: climate influences aerosol concentrations through changes in temperature and radiation, while aerosols impact the climate by directly blocking sunlight or altering cloud properties. Although these processes are closely linked to our future, estimating their effects is highly complex due to numerous uncertainties in aerosol chemistry, optics, cloud microphysics, biogenic emissions, anthropogenic activities, and more. We are continuously improving scientific methods and breaking down the various factors to better assess the climate and health impacts of air pollutants.