Applied Sciences

Research

14 pages, 3588 KiB

Open AccessArticle

Performance Evaluation of Planetary Boundary Layer Schemes in Simulating Structures of Wintertime Lower Troposphere in Seoul Using One-Hour Interval Radiosonde Observation

by Beom-Soon Han, Kyung-Hwan Kwak, Jae-Hee Hahm and Seung-Bu Park

Appl. Sci. 2022, 12(13), 6356; https://doi.org/10.3390/app12136356 - 22 Jun 2022

Cited by 2 | Viewed by 1990

Abstract

We investigated the structures of the wintertime lower troposphere in Seoul, South Korea on 17 and 18 January 2017 by performing 1 h interval radiosonde observation and numerical simulations. In the daytime on 17 January, the height of the convective boundary layer (CBL) [...] Read more.

We investigated the structures of the wintertime lower troposphere in Seoul, South Korea on 17 and 18 January 2017 by performing 1 h interval radiosonde observation and numerical simulations. In the daytime on 17 January, the height of the convective boundary layer (CBL) sharply and quickly increased when the residual layer became a part of the CBL. From the afternoon on 17 January, moist air with clouds began to substantially intrude in the lower troposphere in Seoul, and radiative heating/cooling weakened. As a result, the mixing of air in the lower troposphere was inhibited and the vertical gradients of potential temperature and water vapor mixing ratio changed little on 18 January. We evaluated the performance of four planetary boundary layer (PBL) parameterization schemes (the Yonsei University (YSU), Mellor–Yamada–Janjić (MYJ), Mellor–Yamada–Nakanishi–Niino (MYNN), and Asymmetric Convective Model version 2 (ACM2) schemes) coupled with the Weather Research and Forecasting model in simulating the structures of the lower troposphere against 1 h interval radiosonde observation. The general tendencies of the air temperature and wind speed in the lower troposphere were well-reproduced in the four simulations. However, the sharp increase in the CBL height did not appear in the four simulations, implying that the process of the residual layer becoming a part of the CBL in the daytime is not well-parameterized. Additionally, the simulated water vapor mixing ratio near the surface was smaller compared with the observation. We found that small-scale turbulence in the CBL, which mixes advected air and pre-existing air, was not reproduced well by the PBL parameterization schemes. Compared with the other simulations, the most accurate air temperature and wind speed were reproduced in the simulation with the MYJ scheme, while the CBL development and moisture advection were reproduced relatively well in the simulation with the MYNN scheme. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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17 pages, 877 KiB

Open AccessArticle

Forecasting Fine-Grained Air Quality for Locations without Monitoring Stations Based on a Hybrid Predictor with Spatial-Temporal Attention Based Network

by Hsun-Ping Hsieh, Su Wu, Ching-Chung Ko, Chris Shei, Zheng-Ting Yao and Yu-Wen Chen

Appl. Sci. 2022, 12(9), 4268; https://doi.org/10.3390/app12094268 - 23 Apr 2022

Cited by 7 | Viewed by 2537

Abstract

Air pollution in cities is a severe and worrying problem because it causes threats to economic development and health. Furthermore, with the development of industry and technology, rapid population growth, and the massive expansion of cities, the total amount of pollution emissions continue [...] Read more.

Air pollution in cities is a severe and worrying problem because it causes threats to economic development and health. Furthermore, with the development of industry and technology, rapid population growth, and the massive expansion of cities, the total amount of pollution emissions continue to increase. Hence, observing and predicting the air quality index (AQI), which measures fatal pollutants to humans, has become more and more critical in recent years. However, there are insufficient air quality monitoring stations for AQI observation because the construction and maintenance costs are too high. In addition, finding an available and suitable place for monitoring stations in cities with high population density is difficult. This study proposes a spatial-temporal model to predict the long-term AQI in a city without monitoring stations. Our model calculates the spatial-temporal correlation between station and region using an attention mechanism and leverages the distance information between all existing monitoring stations and target regions to enhance the effectiveness of the attention structure. Furthermore, we design a hybrid predictor that can effectively combine the time-dependent and time-independent predictors using the dynamic weighted sum. Finally, the experimental results show that the proposed model outperforms all the baseline models. In addition, the ablation study confirms the effectiveness of the proposed structures. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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18 pages, 6736 KiB

Open AccessArticle

Validating Aerosol Optical Depth Estimation Methods Using the National Institute of Environmental Research Operational Numerical Forecast Model

by Hye-Jin Kim, Uju Shin, Won Jun Choi, Ja-Ho Koo, Chang H. Jung, Ki-Pyo Nam and Sang-Hun Park

Appl. Sci. 2022, 12(5), 2556; https://doi.org/10.3390/app12052556 - 28 Feb 2022

Viewed by 2210

Abstract

Currently, significant efforts are being made to enhance the performance of the National Institute of Environmental Research (NIER) operational model. However, the model performance concerning Aerosol Optical Depth (AOD) estimation remains uninvestigated. In this study, three different estimation methods for AOD were implemented [...] Read more.

Currently, significant efforts are being made to enhance the performance of the National Institute of Environmental Research (NIER) operational model. However, the model performance concerning Aerosol Optical Depth (AOD) estimation remains uninvestigated. In this study, three different estimation methods for AOD were implemented using the NIER operational model and validated with satellite and ground observations. In the widely used Interagency Monitoring of Protected Visual Environments (IMPROVE) method, AOD exponentially increases with relative humidity owing to a hygroscopic growth factor. However, alternative methods show better performance, since AOD estimation considers the size dependency of aerosol particles and is not sensitive to high relative humidity, which reduces the high AOD in areas with large cloud fractions. Although some R values are significantly low, especially for a single observational comparison and small numerical domain analysis, one of the alternative estimation methods achieves the best performance for diagnosing AOD in the East Asia region. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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20 pages, 5629 KiB

Open AccessArticle

Airborne Particulate Matter Modeling: A Comparison of Three Methods Using a Topology Performance Approach

by Julio Alberto Ramírez-Montañez, Marco Antonio Aceves-Fernández, Jesús Carlos Pedraza-Ortega, Efrén Gorrostieta-Hurtado and Artemio Sotomayor-Olmedo

Appl. Sci. 2022, 12(1), 256; https://doi.org/10.3390/app12010256 - 28 Dec 2021

Cited by 2 | Viewed by 1732

Abstract

Understanding the behavior of suspended pollutants in the atmosphere has become of paramount importance to determine air quality. For this purpose, a variety of simulation software packages and a large number of algorithms have been used. Among these techniques, recurrent deep neural networks [...] Read more.

Understanding the behavior of suspended pollutants in the atmosphere has become of paramount importance to determine air quality. For this purpose, a variety of simulation software packages and a large number of algorithms have been used. Among these techniques, recurrent deep neural networks (RNN) have been used lately. These are capable of learning to imitate the chaotic behavior of a set of continuous data over time. In the present work, the results obtained from implementing three different RNNs working with the same structure are compared. These RNNs are long-short term memory network (LSTM), a recurrent gated unit (GRU), and the Elman network, taking as a case study the records of particulate matter

{PM}_{10}

and

{PM}_{2.5}

from 2005 to 2019 of Mexico City, obtained from the Red Automatica de Monitoreo Ambiental (RAMA) database. The results were compared for these three topologies in execution time, root mean square error (RMSE), and correlation coefficient (CC) metrics. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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14 pages, 1454 KiB

Open AccessArticle

Comparison of PM_2.5 in Seoul, Korea Estimated from the Various Ground-Based and Satellite AOD

by Sang-Min Kim, Ja-Ho Koo, Hana Lee, Jungbin Mok, Myungje Choi, Sujung Go, Seoyoung Lee, Yeseul Cho, Jaemin Hong, Sora Seo, Junhong Lee, Je-Woo Hong and Jhoon Kim

Appl. Sci. 2021, 11(22), 10755; https://doi.org/10.3390/app112210755 - 15 Nov 2021

Cited by 13 | Viewed by 3165

Abstract

Based on multiple linear regression (MLR) models, we estimated the PM_2.5 at Seoul using a number of aerosol optical depth (AOD) values obtained from ground-based and satellite remote sensing observations. To construct the MLR model, we consider various parameters related to the [...] Read more.

Based on multiple linear regression (MLR) models, we estimated the PM_2.5 at Seoul using a number of aerosol optical depth (AOD) values obtained from ground-based and satellite remote sensing observations. To construct the MLR model, we consider various parameters related to the ambient meteorology and air quality. In general, all AOD values resulted in the high quality of PM_2.5 estimation through the MLR method: mostly correlation coefficients >~0.8. Among various polar-orbit satellite AODs, AOD values from the MODIS measurement contribute to better PM_2.5 estimation. We also found that the quality of estimated PM_2.5 shows some seasonal variation; the estimated PM_2.5 values consistently have the highest correlation with in situ PM_2.5 in autumn, but are not well established in winter, probably due to the difficulty of AOD retrieval in the winter condition. MLR modeling using spectral AOD values from the ground-based measurements revealed that the accuracy of PM_2.5 estimation does not depend on the selected wavelength. Although all AOD values used in this study resulted in a reasonable accuracy range of PM_2.5 estimation, our analyses of the difference in estimated PM_2.5 reveal the importance of utilizing the proper AOD for the best quality of PM_2.5 estimation. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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16 pages, 12198 KiB

Open AccessArticle

Effects of Fences and Green Zones on the Air Flow and PM_2.5 Concentration around a School in a Building-Congested District

by Soo-Jin Park, Geon Kang, Wonsik Choi, Do-Yong Kim, Jinsoo Kim and Jae-Jin Kim

Appl. Sci. 2021, 11(19), 9216; https://doi.org/10.3390/app11199216 - 3 Oct 2021

Cited by 3 | Viewed by 2003

Abstract

We investigated the effects of wall- and tree-type fences on the airflow and fine particular matter (PM_2.5) concentration around a school using a computational fluid dynamics (CFD) model. First, we validated the simulated wind speeds and PM_2.5 concentrations against measured [...] Read more.

We investigated the effects of wall- and tree-type fences on the airflow and fine particular matter (PM_2.5) concentration around a school using a computational fluid dynamics (CFD) model. First, we validated the simulated wind speeds and PM_2.5 concentrations against measured values, and the results satisfied the recommended criteria of the statistical validation indices used. Then, we evaluated the fence effects for 16 inflow directions by conducting numerical simulations with different fence types and heights. With east–southeasterly inflow, relatively high PM_2.5 from the road was transported to the school. However, the wall-type fence prevented the PM_2.5 from the road from entering the school, and the PM_2.5 concentration decreased significantly downwind of the fence. With east–northeasterly inflow, the horizontal wind speed decreased due to the drag caused by the tree-type fence, resulting in a shift in the flow convergence region. The PM_2.5 concentration decreased in the region of strengthened upward flow. This occurred because the number of pollutants transported from the background decreased. A comparison of the two fence types revealed that the effect of the tree-type fence on inbound pollutants was more significant, due to increased upward flows, than the effect of the wall-type fence. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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19 pages, 5412 KiB

Open AccessFeature PaperArticle

Intra–Community Scale Variability of Air Quality in the Center of a Megacity in South Korea: A High-Density Cost-Effective Sensor Network

by Yongmi Park, Ho-Seon Park, Subin Han, Kyucheol Hwang, Seunghyun Lee, Jin-Young Choi, Jae-Bum Lee, Sang-Hyun Lee, Kyung-Hwan Kwak, Jae-Jin Kim and Wonsik Choi

Appl. Sci. 2021, 11(19), 9105; https://doi.org/10.3390/app11199105 - 30 Sep 2021

Cited by 6 | Viewed by 2400

Abstract

To investigate the spatial and temporal variability of air quality (CO, NO₂, O₃, and PM_2.5) with a high spatial resolution in various adjacent micro-environments, 30 sets of sensor-nodes were deployed within an 800 × 800 m monitoring [...] Read more.

To investigate the spatial and temporal variability of air quality (CO, NO₂, O₃, and PM_2.5) with a high spatial resolution in various adjacent micro-environments, 30 sets of sensor-nodes were deployed within an 800 × 800 m monitoring domain in the center of the largest megacity (Seoul) in South Korea. The sensor network was operated in summer and winter. The daily variation in air pollutant concentrations revealed a similar trend, with discernible concentration differences among monitoring sub-sites and a government-operated air quality monitoring station. These differences in pollutant levels (except PM_2.5) among the sub-sites were pronounced in the daytime with high volumes of traffic. The coefficient of divergence and Pearson correlation coefficient showed that spatial and temporal variability was more significant in summer than winter. Ozone displayed the greatest spatial variability, with little temporal variability among the sub-sites and a negative correlation with NO₂, implying that ozone concentrations were primarily determined by vehicular NO_X emissions due to NO titration effects under the urban canopy. The PM_2.5 concentration displayed homogeneous spatial and temporal distributions over the entire monitoring period, implying that PM_2.5 monitoring with at least a 1 × 1 km resolution is sufficient to examine the spatial and temporal heterogeneity in urban areas. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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Graphical abstract

11 pages, 1399 KiB

Open AccessArticle

Spatial Concentration of Carbon Components in Indoor PM_2.5 of School Classrooms in a Large City of Korea

by Sujeong Heo, Jiyou Kwoun, Sumin Lee, Doyoon Kim, Taejung Lee and Youngmin Jo

Appl. Sci. 2021, 11(16), 7328; https://doi.org/10.3390/app11167328 - 9 Aug 2021

Cited by 3 | Viewed by 1604

Abstract

On increasing the importance of indoor air quality in urban schools of Korea, a comprehensive investigation of PM_2.5 was carried out focusing on carbon contents. According to the analysis results, PM_2.5 of the classrooms distributed 14.5 μg/m³ to 40.2 μg/m [...] Read more.

On increasing the importance of indoor air quality in urban schools of Korea, a comprehensive investigation of PM_2.5 was carried out focusing on carbon contents. According to the analysis results, PM_2.5 of the classrooms distributed 14.5 μg/m³ to 40.2 μg/m³, which was lower than National Guidelines (35 μg/m³ for 24 h average), and it contained 45.4 ± 10.9% of carbonaceous matters including organic carbon (OC) and elemental carbon (EC). Carbons were proportionally correlated with externally occurring ion species, but OC was found more inside (9.5 μg/m³) than outside (5.9 μg/m³). This indicates that school children are exposed to a variety of polymeric chemicals in the classroom. The current data obtained in this study can be used to inform the establishment of a national school air quality management policy. Full article

(This article belongs to the Special Issue Advances in Monitoring and Modeling of Urban Air Quality)

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