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To establish and implement effective policies for controlling fine particle matters (PM2.5), which is associated with high-risk diseases, continuous research on identifying PM2.5 sources was conducted. This study utilized the positive matrix factorization (PMF) receptor model to estimate the sources and characteristics of PM2.5 between Baengnyeong Island (BNI) and the Seoul Metropolitan Area (SMA). We conducted PMF modeling and backward trajectory analysis using the data on PM2.5 and its components collected from 2020 to 2021 at the Air quality Research Centers (ARC). The PMF modeling identified nine pollution sources in both BNI and the SMA, including secondary sulfate, secondary nitrate, vehicles, biomass burning, dust, industry, sea salt particles, coal combustion, and oil combustion. Secondary particulate matter, vehicles, and biomass burning were found to be major contributors to PM2.5 concentrations in both regions. A backward trajectory analysis indicated that air masses, passing through BNI to the SMA, showed higher concentrations and contributions of ammonium nitrate, vehicles, and biomass burning in the SMA site compared to BNI site. These findings suggest that controlling nitrogen oxides (NOx) and ammonia emissions in the SMA, as well as monitoring the intermediate products that form aerosols, such as HNO3, are needed. [ABSTRACT FROM AUTHOR]

This study aimed to develop a method for assessing landscapes using environmental data and user-generated data, which are commonly employed in landscape research. It focused on the Seoul metropolitan area in South Korea, devising evaluation indicators for five key concepts: naturalness, diversity, imageability, historicity, and disturbance. These indicators were used to assess the landscapes based on each index. We employed a self-organizing map, an artificial neural network technique, to categorize the landscape units and developed eight evaluation indicators for the five key concepts, organizing the study area's landscapes into six distinct landscape units. This study identified landscape unit types with increased vulnerability to visual blight or heightened public awareness by considering both user characteristics and environmental attributes in the metropolitan area landscapes. Finally, we discussed future tasks for appropriate landscape management based on each landscape area's characteristics to maintain and enhance landscape quality. [ABSTRACT FROM AUTHOR]

The spatiotemporal inhomogeneity of the total column NO2 amounts (TCN) in the Seoul Metropolitan Area (SMA), Korea, was quantitatively assessed through year-round (October 2019–May 2021) TROPOMI and ground-based Pandora measurements. The average TCN over the SMA was comparable to that of major Chinese megacities, being consistently high (> 0.8 DU; Dobson Unit) during the daytime (10–17 local standard time). The autocorrelation scores of the Pandora-measured TCNs demonstrated high temporal variability attributed to the spatial inhomogeneity of NO2 emissions within the SMA and near-surface advection. Accordingly, the adequate temporal collocation range for Pandora measurements for the intercomparison with the satellite sensors was considered to be ± 5 min to avoid significant uncertainty from the temporal variability (RMSE < 0.1 DU, R2 > 0.96). TROPOMI showed better agreement with conventionally collocated Pandora measurements (0.73

Major earthquakes in continental regions may cause significant damage. Preexisting fault system across megacity receives high attention for possible seismic damages. Earthquake occurrence mechanism is important to assess the geohazard potentials. Continental‐scale Quaternary fault system is developed across the Seoul metropolitan area where the population is the largest in the Korean Peninsula. Historical seismic‐damage records suggest potential seismic hazards in the Seoul metropolitan area. We investigate the fault motions and spatial distribution of earthquakes in the Seoul metropolitan area using a matched‐filter technique that is based on stacked waveform crosscorrelation functions among densely‐deployed seismic stations. The analysis detects 1103 earthquakes that include 360 events with magnitudes (ML) of −0.6 to 2.0 around the Chugaryeong fault and 34 events with magnitudes of −0.5 to 2.7 around Wangsukcheon, Pocheon, and Yeseonggang faults. The seismicity suggests a set of near‐vertical subparallel (or orthogonal) faults that develop from the major faults. A major fault system behaves as a backbone structure that makes branch faults develop, producing seismicity including major earthquakes. The backbone structure may control the fault development that conforms to the ambient stress field. The backbone faults may play a role to increase geohazard potentials. Plain Language Summary: The Seoul metropolitan area is the most populated region in the Korean Peninsula. Historical seismic damage records and major Quaternary faults suggest high seismic hazard potentials in the region. The identification of earthquake‐spawning faults is crucial for seismic hazard mitigation. We illuminate the earthquake‐spawning faults from micro to small earthquakes in the Seoul metropolitan. We perform a matched‐filter analysis to find earthquakes in adjacent locations of reported events. Recently‐deployed temporary dense seismic stations allow us to detect microearthquakes in high ambient‐noise environments of the megacity. We detect 1103 earthquakes that include 360 events with magnitudes (ML) of −0.6 to 2.0 around the Chugaryeong fault and 34 events with magnitudes (ML) of −0.5 to 2.7 around Wangsukcheon, Pocheon, and Yeseonggang faults. The earthquake distribution suggests the presence of active near‐vertical subparallel or conjugate faults along the major Quaternary faults that may behave as backbones of earthquake‐spawning faults. Key Points: Micro to small earthquakes occur around Quaternary faults in the Seoul metropolitan areaSubvertical strike‐slip faults develop along the Quaternary faults, responding to the ambient stress fieldClustered earthquakes occur along conjugate or subparallel faults [ABSTRACT FROM AUTHOR]

Over the past few years, peroxyacetyl nitrate (PAN) has drawn significant attention as a key indicator of photochemical pollution owing to its intimate relationship with ozone and associated health effects. This study presents measurements conducted at the Korea University campus in Seoul during the high-ozone seasons from 2018 to 2021. PAN concentration was measured using fast gas chromatography with luminol chemiluminescence detection (GC-LCD), alongside measurements of O 3 , volatile organic compounds (VOCs), NO, NO 2 , and meteorological variables, including boundary layer height (BLH). The mean concentrations of PAN and O 3 over the years were 0.56 ppbv and 35 ppbv in 2018, 1.29 ppbv and 58 ppbv in 2019, 0.21 ppbv and 50 ppbv 2020, and 0.53 ppbv and 46 ppbv in 2021, respectively. The annual variation observed in Seoul is consistent with trends seen in major cities worldwide during the COVID19 pandemic, reflecting a substantial reduction in urban emissions. Notably, the mean concentration of NOx and VOCs decreased significantly by more than 50 % and 25%, respectively, from 2019 to 2021. At temperatures above 30 °C, PAN decomposition was accelerated, decoupling a consistent positive relationship between PAN and O 3 in 2020 and 2021. The results of a 0-D photochemical model (F0AM) calculation demonstrated that PAN formation primarily stems from anthropogenic VOCs, particularly > C2 alkenes. Elevated PAN concentrations during nighttime were attributed to boundary layer expansion and upper-air entrainment. Instances where PAN concentrations surged to at least 3 ppbv or higher in 2019 were attributed to biomass burning impacted air, as evidenced by concurrent elevations in K+ and OC in PM 2.5 , and O 3. This study underscores the complex interplay of factors influencing PAN and ozone enhancements under decreased precursor levels, with an emphasis on dynamic change in the boundary layer, and long-distance transport of non-fossil sources during agricultural burning seasons. [Display omitted] • PAN variations correlate mainly with precursor changes, with very high PAN levels occurring under specific conditions. • Evening PAN and O 3 surges linked to a sudden rise in boundary layer, suggesting PAN-rich air entrainment from upper layers. • PAN rises with PM2.5 in continental outflow, making PAN a strong photochemical indicator of secondary pollutants. [ABSTRACT FROM AUTHOR]

The Seoul metropolitan area, the most densely populated part of the Korean Peninsula, features complex subsurface structures and seismogenic faults, though their characteristics remain ambiguous due to low seismicity and limitations in fault investigation. High-resolution velocity models can provide constraints for identifying subsurface faults by detecting elongated low-velocity anomalies along fault zones. Recently, a dense seismic network was deployed in this area, facilitating the use of Helmholtz tomography, an array-based method that accounts for finite-frequency effects. Utilizing Helmholtz tomography, we obtained a high-resolution S-wave velocity model down to a depth of 50 km with waveform data recorded at 74 broadband seismic stations. We found that a linear low-velocity anomaly along the Pocheon fault extends to the uppermost mantle, with an increasing width with depth. In contrast, the Dongducheon fault, which traverses Seoul from north to south, is not well imaged, indicating its current weak activity. Another linear low-velocity anomaly extends southwest through Seoul from northern Seoul, potentially representing the extension of the Pocheon fault based on similar strike and dip directions. Additionally, a large lateral low-velocity anomaly is identified in the lower crust beneath the northern part of the Seoul metropolitan area, interpreted as a ductile décollement, connected with the Pocheon, Wangsukcheon, and possibly Gyeonggang faults. This study successfully identified the extensions and orientations of subsurface faults beneath the Seoul metropolitan area down to the uppermost mantle, which is critical for seismic hazard predictions and earthquake simulations in this highly populated area. • A high-resolution S-velocity model is obtained for the Seoul metropolitan area. • A low-velocity anomaly along the Pocheon fault extends to the uppermost mantle. • The width of the Pocheon fault increases with depth. • A large lateral low-velocity anomaly is identified in the lower crust. • The large anomaly in the lower crust is likely a ductile décollement. [ABSTRACT FROM AUTHOR]

We analyzed the multi-year relationship between particulate matter (PM10 and PM2.5) concentrations and possible precursors including NO2, SO2, and NH3 based on local observations over the Seoul Metropolitan Area (SMA) from 2015 to 2017. Surface NH3 concentrations were obtained from Cross-track Infrared Sounder (CrIS) retrievals, while other pollutants were observed at 142 ground sites. We found that NH3 had the highest correlation with PM2.5 (R = 0.51) compared to other precursors such as NO2 and SO2 (R of 0.16 and 0.14, respectively). The correlations indicate that NH3 emissions are likely a limiting factor in controlling PM2.5 over the SMA in a high-NOx environment. This implies that the current Korean policy urgently requires tools for controlling local NH3 emissions from the livestock industry (for example, from hog manure). These findings provide the first satellite-based trace gas evidence that implementing an NH3 control strategy could play a key role in improving air quality in the SMA. [ABSTRACT FROM AUTHOR]

Meteorology and emissions play very important roles in the concentrations of air pollutants during severe haze/smog periods. This study compares the impacts of synoptic meteorology and nationwide/local emissions during high PM10 multi-event and non-event days in the Seoul Metropolitan Area (SMA). The multi-event and non-event cases were selected based on daily mean PM10 concentrations in Seoul from January 2014 to March 2019. The multi-event cases in spring and winter were closely associated with weak synoptic winds, while that in autumn was due to the strong winds at the rear side of a strong cold front, which induced the Asian dust event in northeastern China and Korea. The multi-event case in spring was found to be mainly due to series of migratory anticyclones, while winter case was due to the stagnant system after northerly winds. The surrounding low pressure systems as well as high pressure systems could be important to determine whether the synoptic systems would be stagnant or not. The fractional contributions of SMA emissions to the mean PM10 and PM2.5 concentrations were 24%-35% and 22%-35% for the multi-event cases, respectively. The contributions to the maximum PM10 and PM2.5 concentrations were larger than those to the mean concentrations by 16%-23% and 19%-26% for the multi-event cases, respectively.

Abstract Quaternary faults run across the Seoul metropolitan area that is the highest population region in the Korean Peninsula. Active fault identification and seismic hazard potential assessment are crucial for public safety. Densely deployed permanent and temporal seismic stations enabled us to detect micro to small earthquakes, allowing us to identify earthquake‐spawning faults in Seoul metropolitan area. The source parameters of 455 earthquakes in 2004–2020 are refined. The Gutenberg‐Richter b value is 0.94. Dominant focal depths are 4–15 km. The focal mechanism solutions of 64 earthquakes are determined using seismic‐wave polarities and amplitude ratios. Strike‐slip earthquakes are dominant in the region. Earthquakes are clustered around the Chugaryeong fault system. The dominant strikes of fault planes range from N20°E to N45°E in the northern and southern Seoul metropolitan areas, suggesting branch fault development locally. The earthquakes in middle‐northern Seoul present N‐S directional strike‐slip motions at depths ∼7.5 km along the Chugaryeong fault, suggesting seismically active near‐vertical faults subparallel with Chugaryeong fault.

This study examined the price spillover effect of housing submarkets in cities in the Seoul metropolitan area in South Korea by using the Granger causality test and vector autoregressive model (VAR). We found that housing prices showed a higher spillover effect within regions with similar housing market characteristics. Additionally, the spatial spillover of housing prices revealed a difference between sales price and jeonse price. The spillover of jeonse price was characterized by mutual influence among neighboring cities, while that of sales price was characterized by the influence being transferred in one direction hierarchically. Furthermore, the effects of housing price indicated a slight difference between sales price and jeonse price. Although jeonse price was mainly affected by a neighboring area (geographic boundary), sales price was more influenced by the city with the highest housing prices. Lastly, the housing price spillover tended to be expansive around the city with the highest price. These results suggest that housing price policies targeting specific regions or areas in Korea must be differentiated according to the type of occupancy (jeonse or sales), and it is essential to consider the externalities when promoting policies in the housing market wherein externalities may be significant. [ABSTRACT FROM AUTHOR]

Quaternary faults run across the Seoul metropolitan area that is the highest population region in the Korean Peninsula. Active fault identification and seismic hazard potential assessment are crucial for public safety. Densely deployed permanent and temporal seismic stations enabled us to detect micro to small earthquakes, allowing us to identify earthquake‐spawning faults in Seoul metropolitan area. The source parameters of 455 earthquakes in 2004–2020 are refined. The Gutenberg‐Richter b value is 0.94. Dominant focal depths are 4–15 km. The focal mechanism solutions of 64 earthquakes are determined using seismic‐wave polarities and amplitude ratios. Strike‐slip earthquakes are dominant in the region. Earthquakes are clustered around the Chugaryeong fault system. The dominant strikes of fault planes range from N20°E to N45°E in the northern and southern Seoul metropolitan areas, suggesting branch fault development locally. The earthquakes in middle‐northern Seoul present N‐S directional strike‐slip motions at depths ∼7.5 km along the Chugaryeong fault, suggesting seismically active near‐vertical faults subparallel with Chugaryeong fault. Plain Language Summary: The Seoul metropolitan area is the largest population region in the Korean Peninsula. More than 20 million people live in the area where Quaternary faults run across. Historical literatures presented high seismic damages in the region. Active fault identification and seismic hazard potential assessment are crucial for public safety. Dense seismic stations were deployed to investigate the seismicity and earthquake‐spawning faults in the Seoul metropolitan area. We refined the source locations of 455 earthquakes in 2004–2020. The focal mechanisms solutions of 64 earthquakes were determined using the seismic‐wave polarities and amplitude ratios. Strike‐slip earthquakes are dominant in the region. The strikes of fault planes range from N20°E to N45°E in the northern and southern Seoul metropolitan areas. Branch faults appear to develop locally according to the ambient stress field. Microseismicity are clustered locally. The earthquakes in middle‐northern Seoul present N‐S directional strike‐slip motions at depths ∼7.5 km along the Chugaryeong fault. The Chugaryeong fault system appears to be seismically active. Key Points: Earthquake‐spawning faults run across the Seoul metropolitan areaChugaryeong fault behaves as a single continuous fault, producing earthquakesBranch faults develop locally by the ambient stress field [ABSTRACT FROM AUTHOR]

• Travel time and cost difference between modes impact commute mode choice. • Commuters significantly prefer driving when transfers are required more than once. • Longer walking distances during transfer and egress affect mode choice. • Commuters from different income and age groups react distinctively. • Policy implications for auto-to-transit modal shifts are elaborated. It is well known that faster and less-expensive transit systems with shorter walking distances, as well as less transfers, are associated with transit use. In this regard, recent studies have focused on estimating transit's competitiveness and further suggested possible policy interventions. However, there were not much attention on measuring travel time and cost differences between transit and auto by considering the temporal variability. In addition, only a limited study have focused on the impact of either walking during transfers on mode choice or the stage of walking that most affects mode choice. This paper provides additional insights into the impact of travel time, cost, and transit burdens on commute mode choice based on the analysis in a transit-oriented mega city, Seoul, Korea. Together with the 2016 household travel survey data, we utilize the web-based route guide information to measure time, cost, and transit burdens for both chosen and non-chosen modes. The results reveal that commuters are significantly affected by the travel time and cost difference between modes. Additionally, the results indicate that the odds of driving increases by 4.7% and 24.3% when commuters have to transfer once or more than once, respectively. Also, commuters were mostly disinclined to walk longer distances during transfer and egress. The effect of time, cost, and transit burdens on mode choice also varied by income and age groups, further implying the group of people that should be focused when devising policies to encourage transit use. To conclude, this paper suggests potential levers for transportation policies to trigger modal shifts toward sustainable modes by using advanced data sources that better estimate the travel characteristics by departure time based on a point-to-point travel survey data. [ABSTRACT FROM AUTHOR]

Although the influence of compact development on travel behavior has been extensively studied over the past decades, additional empirical evidence is needed to better understand that effect. This study explores the influences of the built environment (BE) on zone-based travel patterns using the 2010 Household Travel Survey data in Korea,. We apply seemingly unrelated regression (SUR) and censored regression models to reveal relationships between the BE and zone-based travel patterns in the SMA. Results indicate that: (1) transit-oriented design promotes public transit and suppresses auto trips; (2) the rail mode is more predominant relative to the bus mode; (3) mixed land use with high-density development and gridded pattern streets have a positive impact on walking; and (4) high density and easy access to rail have positive influences on reducing distance traveled by automobiles. Our results suggest that a differentiated strategy is needed to improve urban sustainability in the SMA. [ABSTRACT FROM AUTHOR]

This study investigated the potential of fine nitrate (NO 3 − in PM 2.5) formation in Seoul Metropolitan Area (SMA) by nighttime dinitrogen pentoxide (N 2 O 5) heterogeneous chemistry during March 16–18, 2016, relatively dry and stagnant early spring days, by intervening N 2 O 5 uptake coefficients (reactive uptake probability, γN 2 O 5) in modeling with WRF-CMAQ. Simulations of a base case and two sensitivity tests with default (Davis et al., 2008), zero and decupled (tenfold) γN 2 O 5 showed that impacts of γN 2 O 5 on NO 3 − and PM 2.5 are sensitive to relative humidity (RH) and sulfate-nitrate-ammonium (SNA) conditions. The base case simulation generally underestimated NO 3 − and PM 2.5 levels in comparison to observations. Even with decupled γN 2 O 5 , modeled NO 3 − and PM 2.5 concentrations showed relatively small increases under conditions that RH is relatively low in the range of 20 to 40% and SNA levels are severely underestimated (e.g., lower by one third) in the base case simulation. Comparisons of NO 3 − and PM 2.5 concentrations in SMA between simulations with differently specified γN 2 O 5 indicated that N 2 O 5 heterogeneous chemistry has potential to (1) form additional nitric acid (HNO 3), (2) further react with ammonia (NH 3) emitted from various sources including agricultural sources outside of SMA urban-core areas, and (3) contribute to NO 3 − and PM 2.5 formation in SMA. Additional modeling and observational studies on heterogeneous N 2 O 5 chemistry are needed to improve our understanding of NO 3 − and PM 2.5 formation and better forecast PM 2.5 pollution levels over SMA or other urban areas with abundant nitrogen oxides emissions and ammonia emissions such as agricultural emissions from surrounding areas. Unlabelled Image • N 2 O 5 heterogeneous chemistry in the PM 2.5 formation was investigated by intervening the uptake coefficient (rN 2 O 5). • Simulations with the improved uptake coefficient (rN 2 O 5) contributed to better PM 2.5 prediction in some conditons. • Observational studies are needed to understand the nitare formation in the areas with abundant NO x and NH 3 emissions. [ABSTRACT FROM AUTHOR]

With growing urban population and expanding urban areas, the importance of understanding urban effects on precipitation keeps increasing. This study attempts to detect urban effects on precipitation in the Seoul Metropolitan Area (SMA), South Korea by analyzing hourly rain gauge data during 2005–2020. Precipitation events are categorized according to 850-hPa wind directions, and the precipitation increase from the upwind to downwind regions are examined for different duration and intensity classes of precipitation events. The downwind precipitation increase is largest in summer (39%), especially in August (64%). The August precipitation is analyzed in detail. Precipitation statistically significantly increases in Seoul for weak winds and 25–50 km downwind of the center of Seoul for westerly winds, and the precipitation increases are largest in the afternoon. For the precipitation increases, the increases in frequency and intensity of precipitation events are responsible. Short-duration and heavy precipitation events associated with small-sized precipitation systems initiated within the SMA are mainly responsible for the precipitation increases. The downwind precipitation increase also occurs for southwesterly, southerly, and southeasterly winds, but the increases are associated with large-sized precipitation systems. • Urban effects on precipitation in the SMA are examined for different wind types. • Precipitation increases from the upwind region to the downwind region of Seoul. • The downwind precipitation increase is largest in summer, especially in August. • For weak and westerly winds, short and heavy precipitation increases downwind. • The increase is related to small systems initiated newly and intensified downwind. [ABSTRACT FROM AUTHOR]

Highlights • This study employed the concepts of critical juncture and path dependence to explore greenbelt and New town policies' change in Seoul since 1971. • In critical junctures there was a clear political motive for the Korean president to drastically change the greenbelts or the New Town programs. • Thereafter critical junctures the policies reinforced trends through path dependence despite the regime changes. • The reviewed history explains why the Korean government built New Towns in the SMA greenbelt in contrast to sustainable development. • The third critical juncture demonstrates that the housing supply program dominated the greenbelts, and recent Korean government's policy. • Developing countries that need solutions for housing shortages that accompany rapid urbanization could learn from Seoul's experiences. Abstract This study reviews greenbelt and New Town policy in Korea's Seoul Metropolitan Area as a case study by developing the step-wise critical juncture and path dependence repetition model originating in the historical institutionalism. The country is considered to be in a developmental state with significant power, and the capital region has been regarded as politically crucial, so the theory is more appropriately applied to the two policies' changes rather than a gradual institutional developmental model. The results found that decisions on the two policies at the presidential level at critical junctures during times of political change were sustained and reinforced until the next juncture, following the path-dependent tendency across regimes and their political orientation. Because the New Town policy has dominated greenbelt policy since the most recent (third) critical juncture in 1997, the latter is vulnerable despite important environmental issues and a reversal is not expected to occur in the near future. [ABSTRACT FROM AUTHOR]

The objective of this study is to address two questions that are pertinent to the issue of transportation and urban spatial structure. First, we investigate whether the improvement of the subway system affects the spatial structure in the Seoul metropolitan area. Second, if so, we examine whether it contributes to the suburbanisation of population and employment or spatial concentration around the urban centre. To do so, we focus on the improvement of the subway system in Seoul metropolitan areas between 2000 and 2010 with micro population and employment data. Because of the interrelationship between population, employment and transportation, we control for the interplay between population, employment and subway network by using a simultaneous equation model. Our results provide several interesting findings. First, the improvement of the subway system plays an important role in changes in urban spatial structure. Second, the improvement of the subway system significantly affects job growth in the urban centre and subcentres in the city of Seoul. Third, the interrelationship between population, employment and public transportation generates redistributive effects that are substantially associated with urban growth and decline, and determine urban spatial structure. [ABSTRACT FROM AUTHOR]

The transformation of the Seoul Metropolitan Area (SMA), South Korea, is relatively unknown despite the rapid suburbanization that has occurred since the late twentieth century. This study examines the area and its evolution between 1985 and 2015. It finds increasing levels of polycentricity in the SMA measured with five indices. With a refined set of metrics, it identifies nine Edge Cities and eight Boomburbs in the SMA that operate as new suburban centers of growth in the area, as well as several types within them. The evolution of the SMA is largely due to the active role of the state in implementing regional planning, as well as the autonomous actions of private companies and citizens. These result in a unique suburban landscape that differs from those of Europe and the US. This study suggests the need for further research on the SMA in search of new models and concepts that theorize new transformations that metropolitan areas experience. [ABSTRACT FROM AUTHOR]

The Satellite Integrated Joint Monitoring of Air Quality (SIJAQ) field campaign was conducted from October 10 to November 25, 2021, to assess air quality across the Korean Peninsula and validate the results of the Geostationary Environment Monitoring Spectrometer (GEMS) employing remote sensing, modeling, and satellite, aircraft, and ground measurements. To integrate all measurements collected during the campaign, synoptic features across the Korean Peninsula were analyzed. We identified cyclones and anticyclones by tracing weather charts and divided the campaign into five periods (P1 to P5): P1 - Sustained marine stagnation (October 10–28, 2021), P2 - Transitional stagnant high (October 29–November 7, 2021), P3 - Continental migratory low (November 8–14, 2021), P4 - Continental migratory high (November 15–21, 2021), and P5 - Continental migratory low (November 22–25, 2021). The synoptic features, such as the locations of stagnant or migratory cyclones and anticyclones were analyzed during the periods, in association with levels of particulate matter with a diameter of less than 2.5 μm (PM 2.5 levels) over the Seoul metropolitan area (SMA). The synoptic characteristics showed that the presence of a high pressure system was well associated with the occurrence of high PM 2.5 level over the SMA, and a pattern of near-surface divergence and descending motions originating from the mid-troposphere. In addition, we identified and compared two PM 2.5 level peaks caused by local accumulation and transboundary transport process. We also investigated the underlying synoptic meteorological mechanisms of these peaks in terms of large-scale dynamic variables, such as geostrophic wind speed, transient synoptic scale features, vorticity, and vorticity advection at 850 hPa geopotential height, which are responsible for transboundary transport and local accumulation-driven process of PM 2.5 in the SMA. • SIJAQ campaign was conducted in 2021 for GEMS validation. • Synoptic features are presented over SMA for the entire SIJAQ campaign. • Local emission vs. external transport were contrasted during the campaign. [ABSTRACT FROM AUTHOR]

This research studies the process and the political decisions that were carried out in the creation of Seoul Metropolitan Area (SMA) in order to respond to a territorial reorganization associated to a public transport supply that resulted in a model of transit-oriented development (TOD). Contemporaneously, the paper studies the normative framework that governs the metropolitan areas in Colombia and its metropolitan public transport, as well as, it studies the structuring of the metropolitan collective public transport system of the Aburrá Valley Metropolitan Area (AVMA). The aim of the research is to understand the process of territorial and transport policy decisions that were held in the SMA, which makes it an example and case of study to contextualize a reorganization of the collective public transportation system in the Colombian case, specifically in the AVMA. The objectives of the research are identifying the regulatory principles of territorial and transport planning, strategies, and instruments used for setting the policy decisions that have a binding character on the operating entities of the collective public transport system. In order to put the characteristics of the AVMA collective public transport bus system in evidence, a comparison between SMA and AVMA was developed. The implications emerged from this comparison are used to generate guidelines through three themes: a) governance; b) financial system and c) operational aspects. The guidelines hope point the reorganization of the public transportation bus system and a future transition to a model of Transport -and People - Oriented Development in the Colombian metropolitan level context.

This research studies the process and the political decisions that were carried out in the creation of Seoul Metropolitan Area (SMA) in order to respond to a territorial reorganization associated to a public transport supply that resulted in a model of transit-oriented development (TOD). Contemporaneously, the paper studies the normative framework that governs the metropolitan areas in Colombia and its metropolitan public transport, as well as, it studies the structuring of the metropolitan collective public transport system of the Aburrá Valley Metropolitan Area (AVMA). The aim of the research is to understand the process of territorial and transport policy decisions that were held in the SMA, which makes it an example and case of study to contextualize a reorganization of the collective public transportation system in the Colombian case, specifically in the AVMA. The objectives of the research are identifying the regulatory principles of territorial and transport planning, strategies, and instruments used for setting the policy decisions that have a binding character on the operating entities of the collective public transport system. In order to put the characteristics of the AVMA collective public transport bus system in evidence, a comparison between SMA and AVMA was developed. The implications emerged from this comparison are used to generate guidelines through three themes: a) governance; b) financial system and c) operational aspects. The guidelines hope point the reorganization of the public transportation bus system and a future transition to a model of Transport - and People - Oriented Development in the Colombian metropolitan level context. [ABSTRACT FROM AUTHOR]

Compact-city planning factors are commonly applicable even to metropolitan areas. In most cases, however, planning policies based on theses factors fail to consider that travel patterns are not uniform in each metropolitan area. Furthermore, the travel pattern of inter- and intra-municipality that results from spatial interaction between a central city and its various sub-centres and suburbs in a metropolitan area has not been fully explored. A consideration of the specific urban system could therefore provide an answer to the question of why certain factors have different effects on the transit modal split and car travel distance between municipalities of a metropolitan area. The aim of this study was therefore to find an effective way to establish compact-city planning policies in municipalities of the Seoul Metropolitan Area (SMA). An investigation of the changed travel pattern in each municipality based on the changed relationship between transit modal split (TMS) and intra-city trip ratio by car (ITR) between 2006 and 2010 found that the SMA became more car-dependent: TMS and ITR of the municipalities declined together, and ITR decreased much more in the outskirts. Based on the relationship between the two factors, the effects of changes in land use and transportation were estimated using a combination of cluster and regression analysis. This revealed that, in municipalities of Seoul and its adjacent sub-centres, there is a need to promote transit-oriented development (TOD) by creating high-density areas within close proximity to city railroad stations. In contrast, it is necessary, in municipalities on the outskirts of the SMA, to restrict large-scale developments, such as large retail centres, and instead promote a mixture of self-sufficient land uses. In the intermediate municipalities that lie between these two, TMS and ITR can be increased through TOD near railroad stations, or ITR alone can be increased through a greater mix of land use. These findings could assist in implementing effective compact-city planning policies in each municipality of the SMA, and could also be applied to the other metropolitan areas in Korea or elsewhere in the world. [ABSTRACT FROM AUTHOR]

To establish area specific control strategy for ambient ozone in the Seoul Metropolitan Area (SMA), the maximum ozone concentration in each local government district in the SMA were estimated by using the OZone Isopleth Plotting Package for Research (OZIPR) model. The modeling period was June 2000 and the emission inventory data used were from National Institute of Environmental Research (NIER). Except the islands of Incheon, whole Seoul and Incheon areas were volatile organic compounds (VOCs) limited, i.e., decreasing the oxides of nitrogen (NOX) emission alone may increase the maximum ozone concentration upto certain point. In Gyeonggi, 12 areas were VOCs limited while 12 areas were in between VOCs limited and NOX limited, i.e., decreasing both NOX and VOCs emission may decrease the maximum ozone concentration. Majority of the estimated ozone values were lower than the measured values. The reason could be inaccuracy in emission inventories and/or transport from other areas. The same calculation was carried out for June 2004 and it was found that Seoul was still in the VOCs limited condition.

The first and last mile (FLM) of transit trips are associated with physical activity, often placing a burden on transit users. FLMs that are short, safe, and convenient to walk could facilitate transit use. Using household travel survey data of the Seoul metropolitan area, we examine how walkability features (e.g., greenness, building and sidewalk density, and level of enclosure) of the FLM mitigate the burdens associated with the FLM. Our results suggest that designing better walking environments could encourage more transit use for low-income commuters, which further provide planning implications for equity. We also find that the moderating effect of walkability is slightly larger for the first mile compared to the last mile. Using urban design practices that enhance walkability, the significance of the FLM burden can be mitigated, further promoting transit use. [ABSTRACT FROM AUTHOR]

Telecommuting is regarded as a sustainable travel-demand management strategy. In investigating how much telecommuting reduces travel, studies typically adopt one method of the following three: (1) multiplying the telecommuting frequency by the round-trip commute distance, (2) measuring travel changes using quasi-experiments, and (3) determining the marginal effect of telecommuting on travel using econometric analyses. However, each approach has methodological limitations, and previous studies fail to take into consideration various aspects of household travel other than the telecommuter's commute. Against this backdrop, this study presents an alternative approach to estimating the impact of the household head's telecommuting on total household travel other than his or her commute travel using data from the 2006 Household Travel Survey in Korea. Our series of stratified tobit regression analyses show that when the household head does not commute, the usual compensatory travel mechanism induces person-kilometers traveled of 2 km. This rebound effect doubles when the household head telecommutes, although not on regular commuting days. The effect suggests that the benefits of telecommuting are significantly less than anticipated. Consequently, planners and policy makers should consider this counteracting effect when predicting the travel reduction effect of telecommuting or determining the level of telecommuting required to achieve environmental policy goals for urban sustainability. [ABSTRACT FROM PUBLISHER]

Enforcement of an air quality standard for PM 2 . 5 in the Seoul metropolitan area (SMA) was enacted in 2015. From May to June of 2016, an international airborne and surface measurement campaign took place to investigate air pollution mechanisms in the SMA. The total and speciated PM 2 . 5 concentrations since 2008 have been measured at an intensive monitoring site for the SMA operated by the National Institute of Environmental Research (NIER). To gain insight on the trends and sources of PM 2 . 5 in the SMA in May, we analyze PM 2 . 5 concentrations from 2009 to 2013 using the measurements and simulations from a 3-dimensional global chemical transport model, GEOS-Chem and its adjoint. The model is updated here with the latest regional emission inventory and diurnally varying NH 3 emissions. Monthly average PM 2 . 5 concentration measured by β -ray attenuation ranges from 28 (2010) to 45 (2013) μ g/m 3 , decreased from 2009 to 2010, and then continuously increased until 2013. The model shows good agreement with the measurements for the daily average PM 2 . 5 concentrations (R ≥ 0.5), and reproduces 10 out of 17 measured episodes exceeding the daily air quality standard (50 μ g/m 3 ). Using the GEOS-Chem adjoint model, we find that anthropogenic emissions from the Shandong region have the largest modeled influence on PM 2 . 5 in Seoul in May. Average contributions to the high PM 2 . 5 episodes simulated by the model are 39% from the Shandong region, 16% from the Shanghai region, 14% from the Beijing region, and 15% from South Korea. Anthropogenic SO 2 emissions from South Korea are negligible with 90% of the total contribution originating from China. Findings from this study may guide interpretation of observations obtained in the KORUS-AQ measurement campaign. [ABSTRACT FROM AUTHOR]

This article، with a focus on the change and transformation process of the approaches and trends affecting the new towns policy، scrutinizes the first and second generations of the new towns in reference to the South Korea as a case study. The first generation of new towns development in South Korea is associated with the rapid growth of urbanization، industrialization and subsequently economic increase of this country. Lack of housing and inadequate housing supply، formation and growth of the informal settlements especially in connection with Seoul، and the subsequent centralization in the Seoul metropolitan area are the main and significant urban challenges of South Korea in this period. The second generation of new towns has been planned first with the aim of housing supply as their main function in the capital region. These cities are the result of approach that follow the qualitative، gradual and planned development in the form of small scale but multiple projects compared to the past. Decentralization of Seoul and Seoul metropolitan area، integrated regional development، and ultimately the balance of South Korea’s national territory are the key purposes of this process، in terms of spatial planning. [ABSTRACT FROM AUTHOR]

A potential source contribution function (PSCF) can indicate the source areas of high air pollutant concentrations using backward trajectories. However, the conventional two-dimensional PSCF (2D-PSCF) cannot consider the emission and transport height of air pollutants. That missing information might be critical because injection height varies depending on the source type, such as with biomass burning. We developed a simple algorithm to account for the height of trajectories with high concentrations and combined it with the conventional PSCF to devise 3D-PSCF. We demonstrate the applicability of the 3D-PSCF by applying it to particulate PAH data collected from September 2006 to August 2007 in Seoul. We found variation in the results from 3D-PSCF with threshold heights from 3,000 to 1,500 m. Applying 2,000 m as the threshold height in the PSCF calculation most clearly determined the possible source areas of air pollutants from biomass fuel burning that were affecting the air quality in Seoul. [ABSTRACT FROM AUTHOR]

To date, aging is one of the most important issues in our society because of its significant socioeconomic impacts. Corresponding concerns about the transportation needs of the elderly have led to a focus on the mobility and quality of life of the elderly and motivated various studies of senior mobility. As the fastest aging country in the world, Korea will need to provide insightful information for an aging society. The purpose of this study is to investigate the difference in travel behavior between the elderly and the nonelderly groups by focusing on travel time budget (TTB), using the 2006 household travel diary survey data from the Seoul metropolitan area. We develop partial least square (PLS) structural equation models to identify major variables that affect the TTB of each of the two groups and then compare the differences between the models. Model results indicate that the significant explanatory variables differ between the two age groups, and the degree to which the variables affect the TTB differs by personal and household characteristics. [ABSTRACT FROM PUBLISHER]

Despite the effort to control SO 2 emission, sulfate is still one of the major inorganic components of PM 2.5 in urban area. Moreover, there is still a lack of understanding of the sulfate formation mechanism via SO 2 oxidation under various ambient conditions. In this study, we focus on sulfate formation during a haze pollution episode in the spring/summertime of 2016 in Seoul Metropolitan Area (SMA). During the pollution episode, PM 2.5 mass concentration exceeded over 60 μg m−3, and sulfate accounted for about 25% of the total PM 2.5 mass concentration. A sharp increase of sulfur oxidation ratio (SOR) values along with aerosol liquid water content (AWC) under humid conditions could be ascribed to an apparent contribution of aqueous-phase oxidation of SO 2 of sulfate formation during the pollution period. Comparisons of SOR values with four representative oxidants for the aqueous-phase oxidation (i.e., NO 2 , H 2 O 2 , O 3 , and TMIs) indicated that TMIs concentration, especially for Mn (II), showed the best positive correlation. Furthermore, for calculating the sulfate production rate, the contribution of TMIs concentration was found to be dominant within the pH range in SMA (2.1–3.0), which was determined by the chemical composition and derived AWC. These results imply that not only the SO 2 emission but also other chemical components (e.g., TMI and nitrate) would play a critical combined role in sulfate formation under urban haze condition. [Display omitted] • Aqueous-phase formation of sulfate occurred importantly during the haze in SMA. • The oxidation by TMIs is the most significant for sulfate formation. • Within the pH ranges in SMA (2.1–3.0), TMIs are the most contributing oxidants. [ABSTRACT FROM AUTHOR]

Although telecommuting has become a popular option as a new mode of working, no theoretical or empirical consensus has been reached on its potential for substituting or generating travel. This study aims to evaluate the impact of a household head’s telecommuting on household travel while controlling for the interdependence within a household and across travel purposes, by applying seemingly unrelated censored regression models to data from the 2006 Household Travel Survey in the Seoul Metropolitan Area. In terms of vehicle kilometers traveled, the analysis shows that telecommuters’ non-commute and non-work trips as well as his/her household members’ non-work trips are greater than those of non-telecommuters and their household members’, whereas telecommuting partially reduces commuting trips. However, an analysis stratified by household type reveals that the difference for household members is significant only in households with less than one vehicle per employed member: in such households (with insufficient vehicles available), the vehicle otherwise used for mandatory travel, such as for the household head’s commute, can be used for non-commute purposes or by other household members if the household head does not use it for commuting. This implies that, when vehicle travel budgets of a given household are limited, this compensatory travel mechanism can make optimum use of limited resources (i.e., vehicles), but offsets the travel-substituting effect of telecommuting. Accordingly, to more precisely estimate the impact of telecommuting-promotion policies and apply them as part of travel demand management strategies, their counteracting effects among household members should be considered. [ABSTRACT FROM AUTHOR]

Using a Juhn–Murphy–Pierce (JMP) decomposition, this study analyses the dynamic changes in regional wage differentials between the Seoul Metropolitan Areas and other regions in South Korea. Data from the Korean Labor and Income Panel Study for three years (2000, 2004, and 2008) is used. JMP decomposition provides information about the components that explain changes in regional wage differentials over time. Between 2000 and 2004, the variations in observed and unobserved components are associated with counteracting effects on regional wage differentials. While changes in observed components contribute more to widen regional wage differentials, those in unobserved components narrow them. However, between 2004 and 2008, both observed and unobserved components move in the same direction to narrow regional wage differentials. Based on our empirical results, we discuss some policy implications. [ABSTRACT FROM AUTHOR]

Abstract: Due to its proximity to the Seoul Metropolitan Area (SMA) (40 km from Seoul proper to North Korea) and the characteristics of energy consumption (coal and biomass burning as major primary energy sources), air pollutants emitted from North Korea are likely to influence the air quality in the SMA. To understand the transport of air pollutants emitted from North Korea, backward trajectories arriving in Seoul were estimated and classified into four cases depending on which area the trajectories predominantly passed through for the sampling days between 2002 and 2003. The ambient data of particulate polycyclic aromatic hydrocarbons (PAHs) were analyzed for the samples. Then, based on the contribution of biomass burning calculated by the chemical mass balance (CMB) model applied and the influence of air pollutants'' emissions from North Korea to SMA is semi-quantified. The result was verified by the spatial and seasonal variations of the PAH emission in China based on the previous works. It is estimated that the influence from North Korea on the particulate PAHs concentration in Seoul was up to 20% of the observed values. Further study directions are discussed to make more quantitative and reliable estimation. [Copyright &y& Elsevier]

Abstract: The performance of the updated Air Quality Forecasting System (AQFS) using Weather Research and Forecasting (WRF v.3.1) and the U.S. EPA''s Models-3/Community Multiscale Air Quality (CMAQ v4.6) with emphasis on PM10 (Particulate Matter with aerodynamic diameters less than 10μm) forecast is evaluated over the Seoul Metropolitan Area (SMA) for 2010. The simulations of the updated and old forecasting systems are compared with air quality and meteorological measurements in the modeling domain. The results of the analysis show that the updated forecasts of daily PM10 can reproduce the magnitude and temporal variation of the observations. The time variations of forecasted PM10 are in good agreement with the observations with the range of Index of Agreement (IOA) over 0.7. The forecasted concentrations of daily PM10 are underestimated in all forecasting regions with a range of Normalized Mean Bias (NMB) from −10.76% in the Seoul Metropolitan to −21.29% in the North Gyeonggi province. The discrepancy can be attributed to uncertainties in emissions, forecasted meteorology and models. Even with persistent uncertainties in emission data, the PM10 forecasts from the updated system with emission inventories of INTEX-B for year 2006 in Asia, as well as CAPSS supplementing fugitive dust and biomass emissions for year 2007 in Korea, perform better than those of the old system, which consists of MM5 (v4.7) and CMAQ (v.4.3) and the emission data from TRACE-P for 2000 in Asia and CAPSS for 2003 in Korea. It is also demonstrated that the forecasting system is effective to detect the onset time of the episode and peak value of PM10 in advance which is mainly caused by the long-range transport of aerosols from eastern China to the SMA. The Probability of Detection (POD) for the “C” category of Air Quality Index (AQI), which indicates a health risk for the sensitive group, improves to over 60% by applying the bias-adjustment of hybrid forecast (HF). [Copyright &y& Elsevier]

To improve the air quality in the Seoul Metropolitan area (SMA), the Korean government has implemented special measures in the 1990s. As part of these measures, the Cap-and-Trade System (CATS) was introduced and executed in July 1, 2007 for the oxides of nitrogen (NOx) and sulfur (SOx) to provide added flexibility for large sources to meet the required emission reductions. However, the trade via the SMA CATS for the air pollutants has not been active because of the limited buyers and sellers within the system as well as limited tradable species. For more flexible operation of the SMA CATS, following strategies have been suggested and their merits are discussed; (1) to link the SMA CATS with the Korea Voluntary Emission Reduction (KVER) program which is a program to manage greenhouse gases (GHGs), and (2) to extend the system, such as extension of the tradable species, participants, and introducing a project-based certification mechanism for pollutants reduction. [Copyright &y& Elsevier]

Abstract: As a study area, Seoul metropolitan area in Korea, where has been experiencing transportation problems including congestions and emissions, currently needs an alternative policy measure at the individual level, instead of large scale infrastructure constructions. Even though some researches based on an activity-based approach dealing with an individual travel behavior have been conducted in Korea, none of them used a simulation framework. Considering a genuine activity-based transportation demand forecast, there is no better option but to introduce the activity-based simulation framework. Among several activity-based simulation frameworks, Feathers will indeed be applied into the study area because it is the most viable and suitable simulation platform for that area in terms of a similar spatial dimension. Although, the application for the study area is possible on Feathers, there are potential problems, including the prohibition of using individual and household data in census, an inconsistent administrative unit in Korea and inappropriate Flemish figures and patterns for the study area. To overcome these problems, IPF for synthesizing population and a comparative study of Flemish and the study area will be applied in this study. Moreover, we plan to integrate an agent-based model with the TDM research in order to complement the activity-based model by predicting an adapted daily schedule to an individual circumstance. [Copyright &y& Elsevier]