기후변화에 따른 미세먼지 대기질 변화 추정 및 관련 정책 지원 연구 = A Study on Estimating Changes in Air Quality Caused by Particulate Matter due to Climate Change and Supporting Relevant Policies for Air Quality Management

다국어 초록 (Multilingual Abstract)

Ⅰ. Background and Necessity of Research
1. Necessity
❏ The air quality problem due to fine particulate matter has not improved dramatically despite efforts to reduce emissions of air pollutants since the 2000s.
ㅇ As a result of the continuous implementation of the management policy for fine particulate matter and its precursors, Seoul’s air pollutant emissions and ultrafine particulate matter concentrations continued to decrease until the early 2010s.
ㅇ The concentration of ultrafine particulate matter has been increasing since 2013 and then decreased slightly from 2017, but now it tends to be stagnant with fluctuations around the annual mean PM2.5 concentration of 25μg/m3.
❏ There are research attempts to clarify the relationship between fine particulate matter concentration and weather conditions and climate change, but studies to make policy improvements are insufficient.
ㅇ Air quality-related studies to date have only been conducted to determine the impact of climate change on air quality or to predict air quality concentrations according to future climate change. Research to draw policy implications by grasping the relationship between air quality and climate change is still inadequate.
ㅇ In recent fine particulate matter-related policies, a detailed diagnosis of the possibility of achieving the target concentration presented in the ‘Comprehensive Plan on Fine Dust’ which takes into account the recent weather conditions and nvestigations of the relationship between weather and air quality at various time scales(the seasonal management system and emergency reduction measures) are being carried out it is necessary to grasp the relationship between weather and air quality from various angles according to such change in air management policy and to derive utilization plans for policy development.
2. Research purpose and scope
❏ Analysis of the relationship between weather and climate change and fine particulate matter air quality
ㅇ Analysis of mid- to long-term change patterns of fine particulate matter air quality and related meteorological factors
ㅇ Analysis of major weather and climate factors affecting the concentration of fine particulate matter
ㅇ Analysis of air quality and meteorological relevance of fine particulate matter in various time scales (annual average, seasonal average, high concentration cases, etc.)
ㅇ Investigation of the mechanisms related to climate change and fine particulate matter air pollution
ㅇ Verification of analysis results and analysis of policy implications
❏ Calculation of contributions of meteorological changes to fine particulate matter concentration and forecasts of changes in fine particulate matter pollution due to climate change
ㅇ Analysis of the contribution of meteorological changes to the fine particulate matter concentration based on the fixed emission-weather change model
ㅇ Development of a meteorological index for the impact of fine particulate matter and verification of the predictability for forecasting fine particulate matter air quality in the future climate
ㅇ Establish the modeling base for forecasting fine particulate matter air quality in the future climate
ㅇ Prediction of fine particulate matter concentrations reflecting climate change and emission reduction targets according to future climate scenarios
ㅇ Verification of analysis results and analysis of policy implications
Ⅱ. Relationship between Ultrafine Particulate Matter Concentration and Weather Conditions: Analysis of the Annual Average Levels
1. Annual average fine particulate matter concentration and changes in meteorological factors
ㅇ The concentration of ultrafine particulate matter in 2019 increased again, shifting from the deceasing trend of three years since 2016.
ㅇ Compared to the previous year, the weather conditions in 2019 created an unfavorable environment for the concentration of fine particulate matter overall, with the increase in temperature, decrease of wind speed, and decrease in precipitation.
2. Confirming the contribution of weather changes to the annual average fine particulate matter concentration
❏ Changes in the annual average ultrafine particulate matter concentration by region due to weather changes compared to 2016
ㅇ After 2012, most regions saw meterological conditions that increased the concentration of ultrafine particulate matter. Taking a look at each region, most regions exhibited similar changes in terms of the concentration level of ultrafine particulate matter; for a certain period of time, however, different trends were observed by region.
❏ Contributions of weather and other(non-weather) factors to concentration compared to 2016
ㅇ Before 2012, the contribution by non-weather factors was dominant, but then it showed a tendency to gradually decrease. Since 2012, the overall concentration has been stagnant without any obvious change in the weather and non-weather factors.
ㅇ According to these results, before 2012, non-weather factors such as changes in domestic and foreign air pollutant emissions were the leading cause for changes in fine particulate matter(weather impact was relatively low), and after 2012, it can be thought that it is hard for people to feel the changes in the concentration which occur due to emission reduction.
Ⅲ. The Relationship between Ultrafine Particulate Matter Concentration and Weather Conditions: Seasonal and Monthly Analysis
1. Analysis of changes in wind speed by season and the contribution of weather changes to fine particulate matter concentration during the recent period
❏ Changes in wind speed by season and the number of days with stagnant air
ㅇ Wind speed over the last 20 years(2001~2019) has shown a tendency to decrease in all seasons since 2014, especially in winter.
❏ Analysis of the contribution of weather changes to the average concentration of fine particulate matter by season based on the simulation model of fixed emissions-weather changes
ㅇ The contribution of meteorological conditions to fine particulate matter concentration was analyzed based on the simulation where a fixed amount of emissions and weather changes were applied for the period of the last 20 years.
ㅇ Compared to 2016, the changes in PM2.5 concentration have been relatively small in winter since 2012(this tends to be the opposite in other seasons); in terms of the degree of fluctuation of particulate matter concentration by season, the weather effects in summer have the widest range of fluctuation while winter shows the narrowest range.
ㅇ In the case of changes in the concentration of each season, the concentration of ultrafine particulate matter tended to increase in most seasons(excluding autumn) due to weather factors.
ㅇ When looking at the rates of increase and decrease of the concentration of ultrafine particulate matter by period P1(2005~2012) and P2(from 2013 onwards, the weather in the period P2 acted as a bad condition for ultrafine particulate matter air quality compared to the previous period, and the range of change in concentrations due to weather factors was relatively small.
2. Analysis of changes in ultrafine particulate matter concentration and the contribution of weather changes under the seasonal management system
❏ Changes in the concentration of ultrafine particulate matter by region under the seasonal management system
ㅇ The concentration of ultrafine particulate matter tended to reach the lowest level in December and the highest level in March during the seasonal management period, and the concentration rapidly increased from the end of 2018 to March 2019, and then decreased rapidly(the lowest in the last 5 years).
ㅇ Fixed emission-weather change simulation results: The weather conditions in 2020 are favorable compared to the previous year, but compared to the recent period of 2016-2019 overall, they are at a modest level. In terms of the average rate of change in the average monthly fine particulate matter concentration in Korea, weather conditions in March are especially favorable with the low concentration of ultrafine particulate matter compared to 2017-2019.
3. Analysis of the conditions by weather factor during the seasonal management period of 2020
❏ Wind(wind direction, wind speed), temperature, and precipitation changes over the period 2015-2020
ㅇ In the case of wind, strong winds from the east were predominant in 2020, which is favorable for both direction and speed.
ㅇ Temperatures were the lowest in 2017-2018 and the highest in 2020, which means it was a very unfavorable weather condition for 2020.
ㅇ In the case of precipitation, it was low in March 2020 during the past five years, but the highest rainfalls were recorded in January and February, which were determined as unfavorable conditions for March 2020 and favorable conditions for January and February.
4. Estimation of changes in non-meteorological factors : domestic and international emission reductions
❏ Trend and cause analysis of changes in ultrafine particulate matter concentration compared to the seasonal management period
ㅇ In the case of the ultrafine particulate matter concentrations observed during the seasonal management period, it was 31μg/m³ in 2016-2017, 30μg/m³ in 2017-2018, 33μg/m³ in 2018-2019, and 25μg/m³ in 2019-2020, all of which are higher than the average concentration range.
ㅇ Simulation results of fixed emission-weather change: Weather conditions in both 2016 and 2017 contributed to the increase in fine particulate matter concentration, and the decrease in concentration due to non-meteorological factors was greater than the increase in concentration due to weather factors.
❏ Estimation of non-weather factors(reduction of domestic emissions) among causes of fine particulate matter concentration variability in simulation results
ㅇ Traffic volume in the Seoul metropolitan area tends to decrease during the 2020 season management period compared to 2019(Hangang-daero 1,181 →1,020 thousand vehicles per day, Cheonggyecheon-ro and Jongno 920 →845 thousand vehicles per day, Gonghang-daero 963→955 thousand vehicles per day, based on the average of traffic volume by January-March), and while the PM_2.5 concentrations measured by two monitoring networks have not much difference in 2020, the PM2.5 concentrations measured by the roadside monitoring networks were generally higher than those measured by the urban air monitoring networks in 2019(Hangang-daero 43μg/m³ → Jung District 35μg/m³, Cheonggyecheon-ro 39μg/m³ →Jongno District 34μ g/m³, Jongno 36μg/m³ →Jongno District 34μg/m³, Gonghang-daero 44μg/m³ →Gangseo-gu 39μg/m³ in 2019).
ㅇ The sharp drop in the ultrafine particulate matter concentration compared to the recent period is considered to be cased by one of the non-weather factors due to the decrease in domestic emissions, such as a decrease in traffic volume in urban areas and a decrease in PM_2.5 concentrations observed.
❏ Estimation of non-weather factors(international emission reductions) among causes of fine particulate matter concentration variability in simulation results
ㅇ The changes in air quality in Korea and China during the 2016-2020 period confirmed that air quality around Wuhan City improved around February 2020(AOD in February and March decreased of 15.4% and 17.2%, respectively, compared to 2019), which can be attributed to plant shutdowns and traffic reduction in China due to the coronavirus.
Ⅳ. Relationship between UltraFine Particulate Matter Concentration and Weather Conditions: Case Analysis of High Concentrations
1. Analysis of the change in the pattern of high fine particulate matter concentration
❏ Changes in the annual frequency, intensity, and the number of days with high concentrations of fine particulate matter
ㅇ In terms of the frequency of high concentration cases of ultrafine particulate matter in Seoul, the number of days with high concentration cases in the P1 period when air quality steadily improved decreases, but the number of occurrences in the P2 period repeatedly increases and decreases.
ㅇ The frequency of long-term high concentration cases during the period when air quality improved(P1), but the frequency of long-term high concentration cases increases after the recent period of 2017(P2).
❏ Changes in the frequency of high concentration cases by season
ㅇ The total numbers of high concentration cases in the P1 and P2 periods are 575 days and 436 days, respectively, and the average annual occurrences are 71.9 days and 62.3 days, respectively, with the overall occurrence of high concentration cases slightly decreasing.
ㅇ Comparing the numbers of seasonal occurrences, the proportion of occurrences in spring(26.5%→36.2%) and winter(33.0% →39.2%) increased and the proportion of occurrences in summer(21.0%→13.1%) and autumn(19.5%→11.5%) decreased during P2 compared to the P1 period.
ㅇ It is estimated that the wind speed in winter and spring has recently greatly decreased compared to summer and autumn seasons, creating favorable conditions for the generation of high concentrations of ultrafine particulate matter.
2. Weather conditions affecting the occurrence of high concentration cases of ultrafine particulate matter
❏ Characteristics of meteorological fields on the date of occurrence of high concentration of ultra fine particulate matter
ㅇ In recent years(P2) high pressure over Eurasia has weakened, mid-latitude high pressure over the Korean peninsula and Asia has been strengthened, and noticeable changes have been made such as high pressure over Alaska and the Aleutian low pressure.
ㅇ he weakening of Ural Blocking has weakened west winds over East Asia causing air stagnation and this results in high concentration cases of fine particulate matter; also, the cyclonic deviations over the northern part of Japan prevents the anticyclonic deviations over Korea from passing, resulting in long-term high concentrations of fine particulate matter.
ㅇ The recent rise in temperature and air pressure in Alaska and the eastern part of the Bering Sea may have caused air stagnation near the Korean Peninsula, contributing to the increase in concentration and the prolonged high concentration.
3. A Study on the relationship between climate change and high fine particulate matter concentration cases on the Korean Peninsula
❏ Effect of large-scale changes in the weather field on fine particulate matter from a climate perspective
ㅇ Despite the recent decrease in emissions on the Korean Peninsula, the number of high concentrations of fine particulate matter has increased since 2013, and the causes for this include various changes in weather fields.
ㅇ The increased concentration of fine particulate matter over the Korean peninsula may be attributed to the strengthened Aleutian Low following a reduction in geopotential height of the North Pacific which results from the decrease in Arctic sea ice, or the weakened high pressure over the upper part of Eurasia and the strengthened high pressure over the upper part of the Northeast Asia, led by the decreased sea ice in the Barents Sea.
ㅇ The change in sea ice area is closely related to warm currents in Alaska and other regions, so the high concentration cases may have increased as fine particulate matter stays on the Korean Peninsula for a long time resulting from the decrease in Arctic sea ice during the P2 period due to the strengthening of the Aleutian Low.
ㅇ Changes in Arctic sea ice and large-scale weather systems due to the recent warming may have a significant impact on the occurrence of the long-lasting high-concentration fine particulate matter cases in Korea.
Ⅴ. Conclusion and Policy Implications
❏ Need to supplement current fine particulate matter related policies
ㅇ As a result of confirming the contribution of meteorological changes to the concentration of ultrafine particulate matter through fixed emission-weather change modeling for the last 20 years, the recent contributions of meteorological factors to the concentration of fine particulate matter is relatively similar to that of non-weather factors. As such, it is necessary to consider climate change as well as emission reduction in air quality management.
ㅇ In order to achieve the goal of the comprehensive fine particulate matter plan, it is necessary to set specific goals such as strengthening the emission reduction target amount and presenting a certain level of the concentration range in consideration of the current situation, which is relatively sensitive to the effects of the weather.
ㅇ When evaluating the performance of domestic policy, it is necessary to evaluate the effect of the weather together and evaluate the policy in an accurate and correct way and seek improvement points.
ㅇ Follow-up studies on mechanisms related to climate change and air quality should be continuously conducted, and air quality forecasts and air management targets need to be set in consideration of weather-related seasonal and mid-term forecasts.