Department of Atmospheric Sciences, Yonsei University

[Seminar] Dr. Haeyoung Lee

on November 5, 2021

The observations of atmospheric CO2 and 14CO2 at KMA/GAW regional stations, their characteristics, and implications.

To understand the carbon cycle at policy-relevant spatial scales, a high density of high-quality CO2 measurement sites is needed. In 2012, the Korea Meteorological Administration (KMA) installed CO2 monitoring systems at Anmyeondo (AMY) in the west, Jejudo Gosan Suwolbong (JGS) in the southwest, and Ulleungdo (ULD) in the east of South Korea. In this presentation their monitoring system, and measurement uncertainty will be presented. We also show the observed CO2 characteristics at each station and comparisons with other east Asia station. The radio carbon (14C) in CO2 was known for the tracer of fossil fuel CO2 contributions. AMY collected air for 14C analysis from 2014 to 2016 to analyze characteristics of fossil fuel CO2. The proxies such as CO and SF6 are used for the calculation of emission ratios from observations to compare to those values from inventories. This study provided information on sources of observed CO2 at AMY and confirms the measurement data can verify and improve reported bottom-up inventories. Here, this result will be discussed briefly.

[Seminar] Prof. Wonbae Jeon

on November 2, 2021

Modeling studies on chemical production/loss of PM2.5 and O3 during their long-range transport

The first study investigates the production/loss of sulfate on the sea surface during its transport from Eastern China to South Korea. Results of the CMAQ simulation show high sulfate (SO42-) concentrations over the sea surface areas between Eastern China and South Korea despite nearly zero emissions. The results from a quantitative analysis using the integrated process rate (IPR) in CMAQ suggest that increasing SO42- concentrations during the transport was mainly attributable to chemical SO42- productions. The chemical production of SO42- over the Yellow Sea can primarily be attributed to the “aerosol process”, which is mainly dependent on weather conditions (e.g., temperature and wind speed) and concentrations of precursors such as SO2 and OH. The results of the analysis of the mechanism of SO42- formation using the Sulfur Tracking Model (STM) show that most chemical SO42- production on the surface of the Yellow Sea is the result of the aqueous-phase chemical reactions following the SO2 oxidation reaction (OH + SO2 → H2SO4 + HO2). The second study presents an analysis of high surface ozone (O3) episodes occurring in a rural area (Chuncheon), which is situated 70 km to the prevailing westerly downwind direction of Seoul Metropolitan Area. Although Chuncheon has much lower emission levels than Seoul, the daily mean and maximum O3 levels were higher in Chuncheon than those in Seoul during the episode days. Results of CMAQ simulation demonstrate that the O3 concentration in the air mass moving from Seoul to Chuncheon was very sensitive to the concentration of nitrogen oxide (NOx) because of abundant biogenic volatile organic compounds (BVOCs). The IPR results also show that the NOx emitted from Seoul strongly affected the high O3 levels over its downwind area, mainly with local BVOC emissions. The produced O3 was gradually accumulated during its transport downwind, leading to an O3 concentration maximum at Chuncheon.

[Seminar] Dr. Haklim Choi

on October 31, 2021

Measurement of atmospheric halogenated compounds and the implication for regional emissions in East Asia

Halogen substances (fluoride, chlorine, bromine, and iodine) are chemical elements that play a fundamental role in the Earth’s atmosphere and are associated with a variety of environmental problems. It is well known that halogens (primarily chlorine and bromine) destroy the Earth’s stratospheric ozone layer and cause the infamous “ozone hole” over Antarctica that was first known in the 1980s. The artificial halogen compounds, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), are representative ozone-depleting substances (ODSs) that have been produced by industry for a variety of uses such as refrigerants, foam blowing agents, propellants, solvents, and fire retardants. For this reason, the consumption and production of these compounds are regulated by the Montreal Protocol to protect the stratospheric ozone layer. Hydrofluorocarbons (HFCs) as an alternative to CFCs and HCFCs, rapidly increased in use, are greenhouse gases (GHG) thousands of times more powerful than CO2 in terms of global warming potential (GWP). Accordingly, the production and consumption of HFCs in developed and developing countries will be phase-down under the Kyoto Protocol and the Kigali Amendment. In terms of economic and industrial in East Asia, which includes China, Korea, and Japan, these halogen compounds are significant factors influencing the climate system. However, research on emission sources and the quantification of these substances is still insufficient. In this presentation, the abundance of halogenated compounds in the atmosphere will be analyzed that observed at Gosan, a regional monitoring site in East Asia that has been operated since 2008 as a part of the Advanced Global Atmospheric Gases Experiment (AGAGE). Moreover, we introduce the estimated regional and country-specific emissions using not only the Interspecies correlation (ISC) method but also the inversion framework, FLEXINVERT+, which applies a Bayesian optimization method based on the FLEXPART (FLEXible PARTicle) Lagrangian transport and dispersion model.

[Seminar] Prof. Masahito Ueyama

on October 22, 2021

Biosphere-atmosphere interaction in boreal ecosystems under changing climate

Boreal forests, so called taiga, occupy the circum-polar land between the north dominated by arctic tundra and south dominated by temperate forests. They occupy approximately 9% of the total land, and accumulate up to 23% of global soil carbon stock. The northern high latitude regions have experienced 3.1 o C warming during the past 40 year; warming speed is three times of the global mean of the warming. In the lecture, I review environmental changes currently happened in the northern high latitudes: sea ice declining, greening vegetation, prolonged growing season of vegetation, permafrost degradation, and increasing and intensified wild fires. Then, I introduce our research activities, monitoring biosphere-atmosphere interaction in boreal forests in Alaska. First, I introduce the eddy covariance method, which is the key technique for monitoring fluxes between ecosystem and the atmosphere. Then, I introduce long-term measurements of CO 2 flux at a lowland black spruce forest on the ice-rich permafrost in Fairbanks, Alaska (US-Uaf site registered in AmeriFlux; Ueyama et al., 2014) and measurements of CO 2 flux at two burned forests after fire (US-Rpf and US-Fcr sites; Ueyama et al., 2019). Finally, I introduce regional CO 2 flux based on the upscaling CO 2 fluxes measured at multiple sites, through international collaborations (Ueyama et al., 2013; Virkkala et al., 2021).

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