Preliminary Analysis of Seasonal Variability and Trend in Column-averaged CO2 from COCCON Observations in South Korea
Year: 2026
Type: conference-abstract
Abstract: Accurate measurement of atmospheric carbon dioxide concentrations is essential for climate change research and greenhouse gas emission monitoring. Ground-based Fourier Transform Infrared (FTIR) spectroscopy is a key technology that precisely measures column-averaged CO2 mole fractions (XCO2) in the atmosphere, supporting satellite validation and regional carbon cycle studies.The Collaborative Carbon Column Observing Network (COCCON) is an international collaborative observation network that measures major atmospheric greenhouse gases using portable solar-tracking Fourier Transform Infrared spectrometers (EM27/SUN) with standardized methodologies. COCCON expands the spatial coverage of ground-based observation networks through the portability and cost-effectiveness of its measurement instruments. This study presents XCO2 observations at the Korea Research Institute of Standards and Science (KRISS, 36.39°N, 127.37°E, 95.8 m a.s.l.) in Daejeon, South Korea, over a period of more than two years and analyzes the seasonal variability and trend.XCO2 was measured using EM27/SUN FTIR spectrometers (SN184, SN206) from November 2022 to July 2025, encompassing more than 120 measurement days and multiple complete seasonal cycles. Spectral analysis was performed using PROFFAST, and daily median values were calculated to minimize outliers. The time series data were fitted with a model combining a linear trend and an annual sinusoidal cycle.The results are as follows. First, the seasonal amplitude was 4.08±0.19 ppm, with maximum concentrations in early March and minimum values in early September. This pattern is consistent with seasonal biosphere-atmosphere CO2 exchange in the Northern Hemisphere, where the spring maximum results from winter fossil fuel emissions and reduced photosynthesis, while the autumn minimum occurs after peak growing season uptake. Second, a significant increasing trend of 3.52±0.19 ppm/year was observed, approximately 41% higher than the recent global mean (~2.5 ppm/year), reflecting the emission characteristics and atmospheric circulation patterns over the Korean Peninsula. Third, the fitted model explained 90.8% of the observed variance (R²=0.908), with an RMSE of 1.45 ppm, demonstrating excellent agreement between observations and model. The observation period of more than two years allowed clear separation and accurate quantification of seasonal variability and the increasing trend. The observed seasonal amplitude and timing are consistent with mid-latitude Northern Hemisphere observation sites, while the elevated growth rate suggests regional CO2 sources or potential influence from surrounding regions.These preliminary results demonstrate that EM27/SUN observations at KRISS successfully captured clear seasonal variability and a significant increasing trend in atmospheric CO2. These measurements provide valuable data for the COCCON network and important constraints on CO2 sources and sinks in the East Asian region. Continued long-term monitoring will be essential for tracking greenhouse gas changes and evaluating emission reduction strategies.
Authors: Miyeon Park, Jeongsoon Lee
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
OpenAlex ID: W7135232178