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국제학술지

공지 (2024. 9. 4.)

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PM2.5 forecast in Korea using the long short-term memory (LSTM) model

Abstract: The National Institute of Environmental Research, under the Ministry of Environment of Korea, provides two-day forecasts, through AirKorea, of the concentration of particulate matter with diameters of ≤ 2.5 μm (PM2.5) in terms of four grades (low, moderate, high, and very high) over 19 districts nationwide. Particulate grades are subjectively designated by human forecasters based on forecast results from the Community Multiscale Air Quality (CMAQ) and artificial intelligence (AI) models in conjunction with weather patterns. This study evaluates forecasts from the long short-term memory (LSTM) algorithm relative to those from CMAQ-solely and AirKorea using observations from 2019. The skills of the one-day PM2.5 forecasts over the 19 districts were 39–70% for CMAQ, 72–79% for LSTM, and 73–80% for AirKorea; the AI forecasts showed comparable skills to the human forecasters at AirKorea. The one-day forecast skill levels of high and very high PM2.5 pollution grades are 31–98%, 31–74%, and 39–81% for the CMAQ-solely, the LSTM, and the AirKorea forecasts, respectively. Despite good skills for forecasting the high and very high events, CMAQ-solely forecasts also generate substantially higher false alarm rates (up to 86%) than the LSTM and AirKorea forecasts (up to 58%). Hence, applying only the LSTM model to the CMAQ forecasts can yield reasonable forecast skill levels comparable to the operational AirKorea forecasts that elaborately combine the CMAQ model, AI models, and human forecasters. The present results suggest that applications of appropriate AI models can greatly enhance PM2.5 forecast skills for Korea in a more objective way.
- 작성자Ho et al.
- 작성일2024.09.04
- 조회수15
- 2023
Rainfall strength and area from landfalling TCs over the North Indian and WNP oceans under increased CO2 conditions

Abstract: Climate change due to greenhouse gases has fueled more intense tropical cyclones (TCs) globally. However, the characteristics rainfall strength (RS) and rainfall area (RA) of TCs and their future changes in regional scales are not yet fully understood. Here, using ultra-high-resolution coupled model simulations, we investigate the dominant factors which control rainfall characteristics of landfalling TCs in the North Indian Ocean (NIO) and western-North Pacific (WNP) and their future change in responses to doubling and quadrupling of atmospheric CO2 concentrations. In the NIO, RS increases more than RA when CO2 rises, but the WNP shows the opposite behavior. We demonstrate that RS is highly related to the lifetime maximum intensity, landfall intensity, and latent heat flux (LHFLX), while RA depends mainly on LHFLX, relative humidity at 600 hPa, and vertical wind shear over the WNP. Our results suggest the need to establish regional-scale adaptation strategies for future changes in landfalling TCs rainfall. Full title: Rainfall strength and area from landfalling tropical cyclones over the North Indian and western North Pacific oceans under increased CO₂ conditions
- 작성자Moon et al.
- 작성일2024.09.04
- 조회수10
- 2023
Recent air quality deterioration on weekends in Seoul, South Korea: A focus on external contribution

Abstract: This study has found that the wintertime (November–March) air quality in Seoul, Korea had been deteriorated in weekends during the period of 2016–2019. Specifically, the concentration of particulate matters (PMs) of aerodynamic diameter less than 2.5 μm (PM2.5) in weekends (Saturday–Sunday) was up to 30% higher than that in the mid-week (Wednesday–Thursday) days (probability value < 0.01). As the weekend PM concentration had been lower than the mid-week values by 10% until 2015, such a sudden change in the intra-weekly air quality is unexpected. This study finds out that the deterioration of air quality in weekends can be attributed primarily to secondary particle formations and external transports from China (Shandong and northeast provinces) and domestic provinces (southern Gyeonggi and Chungcheong in Korea) to Seoul. High concentration of PM2.5 on weekend could be partially explained by the differences in the concentrations of inorganic PM components including nitrate, ammonium, and sulfate between weekends and mid-week days. About 40% of the differences are attributed to the domestic sources located in the southern region to Seoul. However, domestic emission from power generations and industry sector in southern source region on weekends does not well explain the variations of the PM precursors in weekends. Therefore, a clear strategy for improving air quality on the weekend in Seoul requires steady efforts to accurately calculate regional emissions and to reveal missing emissions sources.
- 작성자Choi et al.
- 작성일2024.09.04
- 조회수7
- 2023
Enhanced seasonal amplitude of atmospheric CO2 by the Southern Ocean

Abstract: The enhanced seasonal amplitude of atmospheric CO2 has been viewed so far primarily as a Northern Hemisphere phenomenon. Yet, analyses of atmospheric CO2 records from 49 stations between 1980 and 2018 reveal substantial trends and variations in this amplitude globally. While no significant trends can be discerned before 2000 in most places, strong positive trends emerge after 2000 in the southern high latitudes. Using factorial simulations with an atmospheric transport model and analyses of surface ocean PCO2 observations, we show that the increase is best explained by the onset of increasing seasonality of air-sea CO2 exchange over the Southern Ocean around 2000. Underlying these changes is the long-term ocean acidification trend that tends to enhance the seasonality of the air-sea fluxes, but this trend is modified by the decadal variability of the Southern Ocean carbon sink. The seasonal variations of atmospheric CO2 thus emerge as a sensitive recorder of the variations of the Southern Ocean carbon sink.
- 작성자Yun et al.
- 작성일2024.09.04
- 조회수8
- 2022
Erratic Asian summer monsoon 2020: COVID-19 lockdown initiatives possible cause for these episodes?

Abstract: The summer (June through September) monsoon 2020 has been very erratic with episodes of heavy and devastating rains, landslides and catastrophic winds over South Asia (India, Pakistan, Nepal, Bangladesh), East Asia (China, Korea, and Japan), and Southeast Asia (Singapore, Thailand, Vietnam, Laos, Cambodia, Philippines, Indonesia). The withdrawal of the summer monsoon over India was delayed by 2 weeks. The monsoon season over East Asia has been the longest. China recorded a Dam burst in the twentieth century. Furthermore, the Korean Peninsula has experienced back-to-back severe tropical cyclones. Could the lockdown activities initiate to control the COVID-19 spread a possible cause for these major episodes? The strict enforcement of the lockdown regulations has led to a considerable reduction of air pollutants—dust and aerosols throughout the world. A recent study based on satellites and merged products has documented a statistically significant mean reduction of about 20, 8, and 50% in nitrogen dioxide, Aerosol Optical Depth (AOD) and PM2.5 concentrations, respectively over the megacities across the globe. Our analysis reveals a considerable reduction of about 20% in AOD over South as well as over East Asia, more-over East Asia than over South Asia. The reduced aerosols have impacted the strength of the incoming solar radiation as evidenced by enhanced warming, more-over the land than the oceans. The differential warming over the land and the ocean has resulted in the amplification of the meridional ocean-land thermal contrast and strengthening of the monsoon flow. These intense features have supported the surplus transport of moisture from the oceans towards the main lands. Some similarity between the anomalous rainfall pattern and the anomalous AOD pattern is discernable. In particular, the enhancement of rainfall, the reduction in AOD and the surface temperature warming match very well over two regions one over West-Central India and the other over the Yangzte River Valley. Results further reveal that the heavy rains over the Yangzte River Valley could be associated with the preceding reduced aerosols, while the heavy rains over West-Central India could be associated with reduced aerosols and also due to the surface temperature warming.
- 작성자Kripalani et al.
- 작성일2024.09.04
- 조회수10
- 2022
Latitudinal variation of the lifetime maximum intensity location of Atlantic tropical cyclones controlled by the AMO

Abstract: The latitude of lifetime maximum intensity (LMI) location (ϕLMI) of Atlantic tropical cyclones (TCs) is related to the Atlantic Multidecadal Oscillation (AMO) with a significant negative correlation for 1948–2018. We objectively classify TC tracks into four patterns, to evaluate the effects of variations in dominant track patterns (track ϕLMI) and intra-pattern ϕLMI (pure ϕLMI) on the total ϕLMI variation. During the warm phases of AMO, the prevailed south-origin track patterns and equatorward pure ϕLMI shifts have almost equally contributed to the equatorward migration of the total ϕLMI. The negative anomaly of potential intensity in the subtropics is responsible for the equatorward shift of pure ϕLMI. Moreover, weak vertical wind shear in the tropics increases the south-origin track patterns. These environmental conditions are associated with the east-strong and west-weak relative sea surface temperature warming during the warm phases that causes anomalous upward and downward motions in the eastern and western Atlantic, respectively. Full title: Latitudinal variation of the lifetime maximum intensity location of Atlantic tropical cyclones controlled by the Atlantic Multidecadal Oscillation
- 작성자Kim et al.
- 작성일2024.09.04
- 조회수7
- 2022
Possible influence of ENSO Modoki and AO on spatiotemporal variability of spring precipitation over the WNP

Abstract: There are two leading modes in boreal spring precipitation over the western North Pacific (WNP). The first leading mode is a dipole pattern between the southern China and Southeast Asia, which have been previously investigated. The second leading mode is a tripole pattern, which this study focused on. The pattern shows that the positive cores are located in the midlatitudes and the tropical WNP, respectively, whereas the negative one extends from the subtropics to the South China Sea. The mode of tripole pattern is predominantly responsible for the actual spring precipitation variation in the subtropics (r = − 0.93). On the other hand, the precipitation variations in the midlatitudes, the tropical WNP, and the South China Sea are not well explained as much as that in the subtropics. The tripole-pattern-related circulation resembles the positive phase of North Pacific Oscillation, possibly associated with the El Niño Modoki and the positive phase of Arctic Oscillation. The circulation corresponds to the northward shift of the WNP subtropical high, which contributes to the precipitation increase and decrease in the midlatitudes and subtropics, respectively. Meanwhile, the weakened Walker circulation in tropical western Pacific accounts for the decreased and the increased precipitation in the South China Sea and the tropical WNP, respectively. The opposite is true for the circulations related to the La Niña Modoki and negative phase of Arctic Oscillation. Full title: Possible influence of ENSO Modoki and Arctic Oscillation on spatiotemporal variability of spring precipitation over the western North Pacific
- 작성자Park et al.
- 작성일2024.09.04
- 조회수8
- 2022
Untangling the contribution of input parameters to an artificial intelligence PM2.5 forecast model using the LRP method

Abstract: The recurrent neural network (RNN), an artificial intelligence algorithm, applied to the predictions based on the Community Multiscale Air Quality operational model has significantly improved the forecast accuracy of the concentrations of particulate matter with a diameter of ≤2.5 μm (PM2.5) in the Seoul metropolitan area of the Republic of Korea. It is challenging to interpret the prediction results and identify the related error sources because the decision-making process of the RNN model is inaccessible. This study evaluated the relevance score of the RNN input variables using the layer-wise relevance propagation (LRP) at 6-hourly forecasts over the winters of 2015–2021 (December through February). The relevance score magnitudes summed over the period from the target prediction time to 2–5 and 4–7 time-steps before it (i.e., the most recent 12–30 h and 24–42 h, respectively) show ∼80% of the total relevance score for one- and two-day forecasts, respectively. The input variables were originally selected by their correlation coefficients with the observed PM2.5 concentration; however, the order of input variable contributions measured by the LRP differs from the order of the correlation coefficients, implying inconsistency between the linear and nonlinear methods. Retraining the RNN model using a subset of variables of high relevance scores is found to yield prediction skills comparable to the original set of input variables. This study can contribute to the improvement of the RNN prediction model by decoding the black box of an artificial intelligence model using the LRP method. Full title: Untangling the contribution of input parameters to an artificial intelligence PM2.5 forecast model using the layer-wise relevance propagation method
- 작성자Kim et al.
- 작성일2024.09.04
- 조회수10
- 2022
Assessing the influence of large-scale environmental conditions on rainfall structure of Atlantic tropical cyclones: An

Abstract: Understanding the mechanisms related to the variations in the rainfall structure of tropical cyclones (TCs) is crucial in improving forecasting systems of TC rainfall and its impact. Using satellite precipitation and reanalysis data, we examined the influence of along-track large-scale environmental conditions on inner-core rainfall strength (RS) and total rainfall area (RA) for Atlantic TCs during the TC season (July–November) from 1998 to 2019. Factor analysis revealed three major factors associated with variations in RS and RA: large-scale low and high pressure systems [factor 1 (F1)]; environmental flows, sea surface temperature, and humidity [factor 2 (F2)]; and maximum wind speed of TCs [factor 3 (F3)]. Results from our study indicate that RS increases with an increase in the inherent primary circulation of TCs (i.e., F3) but is less affected by large-scale environmental conditions (i.e., F1 and F2), whereas RA is primarily influenced by large-scale low and high pressure systems (i.e., F1) over the entire North Atlantic and partially influenced by environmental flows, sea surface temperature, humidity, and maximum wind speed (i.e., F2 and F3). A multivariable regression model based on the three factors accounted for the variations of RS and RA across the entire basin. In addition, regional distributions of mean RS and RA from the model significantly resembled those from observations. Therefore, our study suggests that large-scale environmental conditions over the North Atlantic Ocean are important predictors for TC rainfall forecasts, particularly with regard to RA. Full title: Assessing the influence of large-scale environmental conditions on rainfall structure of Atlantic tropical cyclones: An observational study
- 작성자Kim et al.
- 작성일2024.09.04
- 조회수10
- 2021
Assessment and valuation of health impacts of fine PM during COVID-19 lockdown: A comprehensive study...

Abstract: A novel coronavirus disease (COVID-19) continues to challenge the whole world. The disease has claimed many fatalities as it has transcended from one country to another since it was first discovered in China in late 2019. To prevent further morbidity and mortality associated with COVID-19, most of the countries initiated a countrywide lockdown. While physical distancing and lockdowns helped in curbing the spread of this novel coronavirus, it led to massive economic losses for the nations. Positive impacts have been observed due to lockdown in terms of improved air quality of the nations. In the current research, ten tropical and subtropical countries have been analysed from multiple angles, including air pollution, assessment and valuation of health impacts and economic loss of countries during COVID-19 lockdown. Countries include Brazil, India, Iran, Kenya, Malaysia, Mexico, Pakistan, Peru, Sri Lanka, and Thailand. Validated Simplified Aerosol Retrieval Algorithm (SARA) binning model is used on data collated from moderate resolution imaging spectroradiometer (MODIS) for particulate matters with a diameter of less than 2.5 μm (PM2.5) for all the countries for the month of January to May 2019 and 2020. The concentration results of PM2.5 show that air pollution has drastically reduced in 2020 post lockdown for all countries. The highest average concentration obtained by converting aerosol optical depth (AOD) for 2020 is observed for Thailand as 121.9 μg/m3 and the lowest for Mexico as 36.27 μg/m3. As air pollution is found to decrease in the April and May months of 2020 for nearly all countries, they are compared with respective previous year values for the same duration to calculate the reduced health burden due to lockdown. The present study estimates that cumulative about 100.9 Billion US$ are saved due to reduced air pollution externalities, which are about 25% of the cumulative economic loss of 435.9 Billion US$. Full title: Assessment and valuation of health impacts of fine particulate matter during COVID-19 lockdown: A comprehensive study of tropical and sub tropical countries
- 작성자Bherwani et al.
- 작성일2024.09.04
- 조회수9
- 2021