[날씨학개론] 보이지 않는 암살자 오존…원인 대처법 / YTN 사이언스

■ Ban Ki-seong / Director of the K-Weather Forecast Center [Anchor] Starting in May, when temperatures suddenly rise, an unwelcome guest arrives. Ozone, an invisible, gaseous air pollutant that even fine dust masks can't filter, is the main character. Today on "Introduction to Meteorology," we'll discuss ozone, which exists on the ground surface. K-Weather Center Director Ban Ki-seong is here. Hello. [Interview] Hello. [Anchor] We usually think of ozone as being distributed in the stratosphere. Could you explain what ground-level ozone is? [Interview] In the 1950s, in Los Angeles, USA, an outbreak occurred where the sky was overcast even on clear days, and many people were hospitalized with eye and throat pain. The state government conducted every epidemiological investigation possible, but the cause was unknown. However, Dr. H. Smith, noting that this phenomenon was worse around 2-3 p.m., when sunlight was at its strongest, discovered the cause. Ozone, created by a photochemical reaction between strong sunlight and automobile exhaust, is said to be the primary culprit behind the hospitalizations. Ozone (O3) is a highly reactive gas composed of three oxygen atoms (O) bonded to an oxygen molecule (O2). It is a colorless gas with a distinctive odor. Its name comes from the Greek word ozein, meaning "to smell." Ozone's strong oxidizing power allows it to eliminate unpleasant odors and serve as a disinfectant and bleaching agent, but it is also a harmful air pollutant. [Anchor] While ozone is a valuable resource in the stratosphere, blocking UV rays, it appears to be a harmful pollutant on the ground. How is ozone created? [Interview] Ozone is not a pollutant directly emitted from automobiles or businesses. It is a secondary pollutant created when air pollutants released into the atmosphere undergo a photochemical reaction when exposed to sunlight. Unlike regular smog, it is called photochemical smog. Ozone is mainly formed during the daytime, when sunlight is strong, the temperature is high, and high concentrations of ozone are produced during periods of clear skies and weak winds. The main ozone-producing substances are nitrogen oxides (NOx) and volatile organic compounds (VOCs), but methane (CH4) and carbon monoxide (CO) are also contributing factors. According to the Ministry of Environment, organic compound emissions have been steadily increasing since 1999, but have been gradually decreasing since 2017. [Anchor] So, you said that ozone is a pollutant that is formed when strong sunlight hits air pollutants. This year, the first ozone advisory was issued on record. Could you explain what causes it and under what conditions an ozone advisory is issued? [Interview] This year, an ozone advisory was issued on March 20th, the first since the introduction of the ozone warning system in 2004. In the 2000s, the first ozone advisory was issued primarily in May. In 2020 and 2021, the first advisory was issued on April 25th and April 20th, respectively. In 2022, it was April 18th. This year, ozone concentrations rose sharply in late March due to strong sunlight and high temperatures starting in early spring in March. Ozone concentrations typically begin to rise when temperatures exceed 25°C. An ozone advisory is a special warning issued by local governments when high ozone concentrations in the atmosphere pose a risk of damage. Depending on the concentration, there are three levels: ozone advisory, ozone warning, and ozone critical warning. An ozone advisory is issued when the ozone concentration exceeds 0.12 ppm per hour, an ozone warning when it exceeds 0.3 ppm, and a critical ozone warning when it exceeds 0.5 ppm. [Anchor] But I heard that not only are these ozone advisories being issued earlier, but the frequency has also increased recently. What's the reason? [Interview] As ozone concentrations continue to rise in Korea, the number and duration of ozone advisories issued each year are increasing. This increase is due to factors such as rising temperatures due to climate change, reduced atmospheric mixing caused by lower average wind speeds, and the long-distance transport of ozone. As temperatures rise, ozone advisories are being issued earlier, while the final advisory date is being delayed. First, looking at the annual changes in ozone concentration in Seoul, where ozone concentrations are highest, the figure shows a steady increase from 2002 to 2022, with the average concentration in 2022 more than double that of 2002. [Anchor] This is a serious situation, with concentrations more than doubling in 20 years. So, which month has the highest ozone concentration in Seoul? [Interview] As you can see in the figure, May and June are the highest, while December is the lowest. June has more than three times the concentration in December. The number of ozone advisories issued in Seoul each year shows an annual increase, with 11 times as many advisories issued in 2022 compared to 2002. Looking at th...