Atmosphere

21 pages, 8034 KiB

Open AccessArticle

PM_2.5 Characteristics and Regional Transport Contribution in Five Cities in Southern North China Plain, During 2013–2015

by Lili Wang, Wenjie Li, Yang Sun, Minghui Tao, Jinyuan Xin, Tao Song, Xingru Li, Nan Zhang, Kang Ying and Yuesi Wang

Atmosphere 2018, 9(4), 157; https://doi.org/10.3390/atmos9040157 - 21 Apr 2018

Cited by 31 | Viewed by 5236

Abstract

PM_2.5 data from major cities in the southern North China Plain during 2013–2015 were comprehensively analyzed relative to variation features, meteorology effects, and regional transport contributions. The annual average ranged from 87 to 123 μg m⁻³, with the highest in [...] Read more.

PM_2.5 data from major cities in the southern North China Plain during 2013–2015 were comprehensively analyzed relative to variation features, meteorology effects, and regional transport contributions. The annual average ranged from 87 to 123 μg m⁻³, with the highest in Baoding and Shijiazhuang, the moderate in Handan and Hengshui, and the lowest in Cangzhou, which revealed an evident concentration gradient with distance from the mountains. PM_2.5 pollution indicated significantly regional characteristics and high correlations in daily PM_2.5 changes and similar seasonal and diurnal variations in five cities. The highest concentrations mainly occurred in the winter, then autumn, spring, and summer, and the diurnal variations were bimodal with peaks during the morning rush hours and at night, which were mostly dominated by the differences in source emissions and the boundary layer. The PM_2.5 concentrations were significantly positively correlated with relative humidity, especially during winter. The highest PM_2.5 concentrations in all cities were associated with the south, southeast, and southwest pathways, while the short northwest pathway in the winter for Baoding and Shijiazhuang experienced the highest concentration. Regional contributions ranged from 19.6 to 33.7% annually, with the largest in Baoding and Shijiazhuang. These results provide a scientific basis for pollution forecasting and control in these heavily polluted cities. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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14 pages, 2418 KiB

Open AccessArticle

Spatial Factor Analysis for Aerosol Optical Depth in Metropolises in China with Regard to Spatial Heterogeneity

by Hui Shi, Qingqing He and Wenting Zhang

Atmosphere 2018, 9(4), 156; https://doi.org/10.3390/atmos9040156 - 20 Apr 2018

Cited by 8 | Viewed by 4431

Abstract

A substantial number of studies have analyzed how driving factors impact aerosols, but they have been little concerned with the spatial heterogeneity of aerosols and the factors that impact aerosols. The spatial distributions of the aerosol optical depth (AOD) retrieved by Moderate Resolution [...] Read more.

A substantial number of studies have analyzed how driving factors impact aerosols, but they have been little concerned with the spatial heterogeneity of aerosols and the factors that impact aerosols. The spatial distributions of the aerosol optical depth (AOD) retrieved by Moderate Resolution Imaging Spectrometer (MODIS) data at 550-nm and 3-km resolution for three highly developed metropolises, the Beijing-Tianjin-Hebei (BTH) region, the Yangtze River Delta (YRD), and the Pearl River Delta (PRD), in China during 2015 were analyzed. Different degrees of spatial heterogeneity of the AOD were found, which were indexed by Moran’s I index giving values of 0.940, 0.715, and 0.680 in BTH, YRD, and PRD, respectively. For the spatial heterogeneity, geographically weighted regression (GWR) was employed to carry out a spatial factor analysis, where terrain, climate condition, urban development, and vegetation coverage were taken as the potential driving factors. The results of the GWR imply varying relationships between the AOD and the factors. The results were generally consistent with existing studies, but the results suggest the following: (1) Elevation increase would more likely lead to a strong negative impact on aerosols (with most of the coefficients ranging from −1.5~0 in the BTH, −1.5~0 in the YRD, and −1~0 in the PRD) in the places with greater elevations where the R-squared values are always larger than 0.5. However, the variation of elevations cannot explain the variation of aerosols in the places with relatively low elevations (with R-squared values approximately 0.1, ranging from 0 to 0.3, and approximately 0.1 in the BTH, YRD, and PRD), such as urban areas in the BTH and YRD. (2) The density of the built-up areas made a strong and positive impact on aerosols in the urban areas of the BTH (R-squared larger than 0.5), while the R-squared dropped to 0.1 in the places far away from the urban areas. (3) The vegetation coverage led to a stronger relief on the AOD in parts of the YRD and PRD (with coefficients less than −0.6 and ranging from −0.4~−0.6, respectively) where there is greater vegetation coverage, and led to a weaker relief on the AOD in the urban area of the PRD with a coefficient of approximately −0.2~−0.4. Full article

(This article belongs to the Special Issue Aerosol Optical Properties: Models, Methods & Measurements)

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12 pages, 14710 KiB

Open AccessArticle

Long-Term Rainfall Trends over the Tanzania Coast

by Tibangayuka Kabanda

Atmosphere 2018, 9(4), 155; https://doi.org/10.3390/atmos9040155 - 20 Apr 2018

Cited by 14 | Viewed by 6035

Abstract

Spatial and temporal rainfall trends over the Tanzanian coast are analysed and trends for over 50 years are investigated. This type of study is crucial at this time because the area under study is now one of the world’s economic hotspots, as major [...] Read more.

Spatial and temporal rainfall trends over the Tanzanian coast are analysed and trends for over 50 years are investigated. This type of study is crucial at this time because the area under study is now one of the world’s economic hotspots, as major gas fields have been discovered and the area also has high potential for oil field discoveries. Methods applied in this study include the Mann-Kendall test for rainfall data to detect the long-term trends, while Sen’s slope estimator test was used for finding the magnitude of change over time. The results exhibited rainfall trend patterns with substantial variations between the stations. The Z value of the Mann-Kendall test showed various months with negative trend at a significance level ≥95%. The few months that showed a positive trend were not statistically significant. Generally, rainfall trends varied in different months for different stations. However, the most outstanding observation on individual months is July, which showed a highly statistically significant (99.9%) reduction in rainfall for the whole coastal area, including the regions of Mtwara, Dar es Salaam and Tanga. The last part of this paper describes the relationship between July rainfall and the horizontal winds from the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) re-analysis. It is observed that the strength of the anticyclonic flow over the southwest Indian Ocean, which is associated with the westward fluxes of moisture, is responsible for rainfall over the whole coastal area of Tanzania during July. Full article

(This article belongs to the Special Issue Precipitation Variability and Change in Africa)

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20 pages, 6251 KiB

Open AccessArticle

Combined Effects of Synoptic-Scale Teleconnection Patterns on Summer Precipitation in Southern China

by Chao Wang and Lijuan Wang

Atmosphere 2018, 9(4), 154; https://doi.org/10.3390/atmos9040154 - 19 Apr 2018

Cited by 16 | Viewed by 6419

Abstract

Using ERA-Interim daily reanalysis and precipitation data, the combined effects of East Asia-Pacific (EAP) and Silk Road (SR) teleconnection patterns on summer precipitation in Southern China were investigated on synoptic to sub-monthly timescales. Combined EAP and SR patterns lead to more persistent and [...] Read more.

Using ERA-Interim daily reanalysis and precipitation data, the combined effects of East Asia-Pacific (EAP) and Silk Road (SR) teleconnection patterns on summer precipitation in Southern China were investigated on synoptic to sub-monthly timescales. Combined EAP and SR patterns lead to more persistent and extreme precipitation in the Yangtze River Valley (YRV) and exhibit an obvious zonal advance between the South Asia High (SAH) and Western Pacific Subtropical High (WPSH) prior to its onset. During typical combined events, an overlap between the SAH and WPSH remains in a favorable position for Persistent Extreme Precipitation (PEP). Furthermore, SR-induced acceleration of the westerly jet stream and extra positive vorticity advection provide persistent upper-level divergence for YRV precipitation. An anomalous EAP-related cyclone/anticyclone pair over East Asia induces enhanced low-level southwesterlies to the northern anticyclone flank and northerlies from the mid-latitudes, advecting anomalously abundant moisture toward the YRV, resulting in clear moisture convergence. Moreover, the strong ascent of warmer/moister air along a quasi-stationary front may be crucial for PEP. During decay, the SAH and WPSH diverge from each other and retreat to their normal positions, and the strong ascent of warmer/moister air rapidly weakens to dissipation, terminating PEP in the YRV. Full article

(This article belongs to the Special Issue Weather and Climate Extremes: Current Developments)

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20 pages, 9466 KiB

Open AccessArticle

Cloud Longwave Scattering Effect and Its Impact on Climate Simulation

by Wenjie Zhao, Yiran Peng, Bin Wang and Jiangnan Li

Atmosphere 2018, 9(4), 153; https://doi.org/10.3390/atmos9040153 - 18 Apr 2018

Cited by 11 | Viewed by 5027

Abstract

The cloud longwave (LW) scattering effect has been ignored in most current climate models. To investigate its climate impact, we apply an eight-stream DIScrete Ordinates Radiative Transfer (DISORT) scheme to include the cloud LW scattering in the General circulation model version of the [...] Read more.

The cloud longwave (LW) scattering effect has been ignored in most current climate models. To investigate its climate impact, we apply an eight-stream DIScrete Ordinates Radiative Transfer (DISORT) scheme to include the cloud LW scattering in the General circulation model version of the LongWave Rapid Radiative Transfer Model (RRTMG_LW) and the Community Atmospheric Model Version 5 (CAM5). Results from the standalone RRTMG_LW and from diagnostic runs of CAM5 (no climate feedback) show that the cloud LW scattering reduces the upward flux at the top of the atmosphere and leads to an extra warming effect in the atmosphere. In the interactive runs with climate feedback included in CAM5, the cloud LW scattering effect is amplified by the water vapor-temperature feedback in a warmer atmosphere and has substantial influences on cloud fraction and specific humidity. The thermodynamic feedbacks are more significant in the northern hemisphere and the resulting meridional temperature gradient is different between the two hemispheres, which strengthens the southern branch of Hadley circulation, and modulates the westerly jet near 50° S and the upper part of Walker circulation. Our study concludes that the cloud LW scattering effect could have complex impacts on the global energy budget and shall be properly treated in future climate models. Full article

(This article belongs to the Special Issue Cloud Radiative Processes and Effect)

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17 pages, 12066 KiB

Open AccessArticle

Atmospheric Emissions from Oil and Gas Extraction and Production in Greece

by Georgios Papailias and Ilias Mavroidis

Atmosphere 2018, 9(4), 152; https://doi.org/10.3390/atmos9040152 - 18 Apr 2018

Cited by 14 | Viewed by 10461

Abstract

This paper addresses the atmospheric emissions of CO₂, SO₂, H₂S, NOx, and volatile organic compounds (VOCs) from oil and gas extraction and production in the Gulf of Kavala. This is currently the only location of oil and [...] Read more.

This paper addresses the atmospheric emissions of CO₂, SO₂, H₂S, NOx, and volatile organic compounds (VOCs) from oil and gas extraction and production in the Gulf of Kavala. This is currently the only location of oil and gas production in Greece. Facilities are located both offshore (Kappa and Delta platforms) and onshore (Sigma plant), producing sweet gas, sour gas, and sour crude oil. This study presents the characteristics of atmospheric emissions, including emission measurements, emission inventories, and concentration measurements, from a central monitoring station and twelve total sulfation stations, the latter aiming to assess the effects of atmospheric emissions to air quality. During the development of the monitoring system, special attention was placed to sulfur compounds, since the existence of sour gas and sour crude oil was expected to lead to increased amounts of H₂S and SO₂. One of the main findings of the present study is that if the prevailing wind direction is considered (i.e., from N–NE), then the central monitoring station is not located downwind of the onshore and offshore facilities; therefore, its position should be re-examined. The emission inventories showed that flaring at the offshore facilities is the main source of SO₂ emissions, while SO₂ emissions and ambient concentrations were well below the relevant standards. Furthermore, CO₂ emissions were lower by 67.73% as compared to 2008, when emissions reached a maximum. This was attributed to more energy demanding activities during that period, and mainly to the operation of turbines between 2007 and 2009. Since it is expected that the exploitation of hydrocarbons as well as oil and gas extraction and production will increase in the future in Greece, appropriate measures should be taken to ensure environmental protection, such as the use of up-to-date emission control technologies and a flare gas recovery system. Full article

(This article belongs to the Special Issue Advances in Atmospheric Physics: Selected Papers from CEST2017)

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19 pages, 65525 KiB

Open AccessArticle

An Uncertainty Investigation of RCM Downscaling Ratios in Nonstationary Extreme Rainfall IDF Curves

by Qiqi Yang, Qiang Dai, Dawei Han, Xuehong Zhu and Shuliang Zhang

Atmosphere 2018, 9(4), 151; https://doi.org/10.3390/atmos9040151 - 18 Apr 2018

Cited by 3 | Viewed by 4133

Abstract

Designed for rainstorms and flooding, hydrosystems are largely based on local rainfall Intensity–Duration–Frequency (IDF) curves which include nonstationary components accounting for climate variability. IDF curves are commonly calculated using downscaling outputs from General Circulation Models (GCMs) or Regional Circulation Models (RCMs). However, the [...] Read more.

Designed for rainstorms and flooding, hydrosystems are largely based on local rainfall Intensity–Duration–Frequency (IDF) curves which include nonstationary components accounting for climate variability. IDF curves are commonly calculated using downscaling outputs from General Circulation Models (GCMs) or Regional Circulation Models (RCMs). However, the downscaling procedures used in most studies are based on one specific time scale (e.g., 1 h) and generally ignore scale-driven uncertainty. This study analyzes the uncertainties in IDF curves stemming from RCM downscaling ratios for four representative weather stations in the United Kingdom. We constructed a series of IDF curves using distribution-based scaling bias-correction technology and a statistical downscaling method to explore the scale-driven uncertainty of IDF curves. The results revealed considerable scale-induced uncertainty of IDF curves for short durations and long return periods; however, there was no clear correlation with the mean storm intensity of the IDF curves of different RCM ensemble members for each duration and return period. The scale-driven uncertainty of IDF curves, which may be propagated or enhanced through hydrometeorological applications, is critical and cannot be ignored in the hydrosystem design process; therefore, a multi-scale method to derive IDF curves must be developed. Full article

(This article belongs to the Special Issue Precipitation: Measurement and Modeling)

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18 pages, 5440 KiB

Open AccessReview

A Review of Airborne Particulate Matter Effects on Young Children’s Respiratory Symptoms and Diseases

by Hai-Ying Liu, Daniel Dunea, Stefania Iordache and Alin Pohoata

Atmosphere 2018, 9(4), 150; https://doi.org/10.3390/atmos9040150 - 16 Apr 2018

Cited by 63 | Viewed by 16523

Abstract

Exposure to airborne fine particulate matter (PM_2.5) carries substantial health risks, particularly for younger children (0–10 years). Epidemiological evidence indicates that children are more susceptible to PM health effects than adults. We conducted a literature review to obtain an overview of [...] Read more.

Exposure to airborne fine particulate matter (PM_2.5) carries substantial health risks, particularly for younger children (0–10 years). Epidemiological evidence indicates that children are more susceptible to PM health effects than adults. We conducted a literature review to obtain an overview of existing knowledge regarding the correlation of exposure to short- and long-term PM concentrations with respiratory symptoms and disease in children. A collection of scientific papers and topical reviews were selected in cooperation with two experienced paediatricians. The literature review was performed using the keywords “air pollution”, “particulate matter”, “children’s health” and “respiratory” from 1950 to 2016, searching the databases of Scopus, Google Scholar, Web of Science, and PubMed. The search provided 45,191 studies for consideration. Following the application of eligibility criteria and experts’ best judgment to titles and abstracts, 28 independent studies were deemed relevant for further detailed review and knowledge extraction. The results showed that most studies focused mainly on the effect of short-term exposure in children, and the reported associations were relatively homogeneous amongst the studies. Most of the respiratory diseases observed in outdoor studies were related to changes in lung function and exacerbation of asthma symptoms. Allergic reactions were frequently reported in indoor studies. Asthma exacerbation, severe respiratory symptoms and moderate airway obstruction on spirometry were also observed in children due to various sources of indoor pollution in households and schools. Mixed indoor and outdoor studies indicate frequent occurrence of wheezing and deterioration of lung function. There is good evidence of the adverse effect of short-term exposure to PM on children’s respiratory health. In terms of long-term exposure, fine particles (PM_0.1–PM_2.5) represent a higher risk factor than coarse particles (PM_2.5–PM₁₀). Additional research is required to better understand the heterogeneous sources and the association of PM and adverse children’s health outcomes. We recommend long-term cooperation between air quality specialists, paediatricians, epidemiologists, and parents in order to improve the knowledge of PM effects on young children’s respiratory health. Full article

(This article belongs to the Special Issue Impacts of Air Pollution on Human Health)

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14 pages, 22854 KiB

Open AccessArticle

The Impacts of Vegetation and Meteorological Factors on Aerodynamic Roughness Length at Different Time Scales

by Mingzhao Yu, Bingfang Wu, Hongwei Zeng, Qiang Xing and Weiwei Zhu

Atmosphere 2018, 9(4), 149; https://doi.org/10.3390/atmos9040149 - 16 Apr 2018

Cited by 9 | Viewed by 3888

Abstract

The aerodynamic roughness length (z_0m) is a crucial parameter for reliably simulating turbulent exchanges between the land surface and the atmosphere. Due to the large number of input variables related to vegetation growth and aerodynamic conditions near the surface, estimating z [...] Read more.

The aerodynamic roughness length (z_0m) is a crucial parameter for reliably simulating turbulent exchanges between the land surface and the atmosphere. Due to the large number of input variables related to vegetation growth and aerodynamic conditions near the surface, estimating z_0m precisely is difficult and, to date, no universal model has been established. Understanding the z_0m changes in time series data and the relative contributions of vegetation indices and meteorological factors is important to providing a basis for modelling z_0m. In this paper, the main meteorological factors that influence z_0m in different seasons are presented based on data from three automatic weather stations (AWSs) that represent various land surface patterns in the Heihe river basin. A correlation analysis identified the dominant factors that influence z_0m changes at half-hour and daily scales; then, a factor analysis was performed to identify the different contributions of vegetation indices and meteorological factors to z_0m at different time scales. The results show that meteorological factors (wind speed, wind direction and atmospheric stability) are the main driving factors for z_0m at the Arou and Guantan sites, which are situated in grassland and forest mountain areas, respectively, and that the vegetation indices have no impact on the z_0m variations in these areas. In contrast, for the Daman site, situated in flat farmland, the vegetation indices are the primary driving factors, while meteorological factors such as wind speed and atmospheric stability are secondary factors, and wind direction has no significant influence. Finally, a detailed analysis was conducted to detect the relationships between half-hourly z_0m measurements and three dominant meteorological factors. Full article

(This article belongs to the Section Biosphere/Hydrosphere/Land–Atmosphere Interactions)

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4 pages, 765 KiB

Open AccessCorrection

Correction: Koutsouris et al. Utilization of Global Precipitation Datasets in Data Limited Regions: A Case Study of Kilombero Valley, Tanzania. Atmosphere, 2017, 8, 246

by Alexander J. Koutsouris, Jan Seibert and Steve W. Lyon

Atmosphere 2018, 9(4), 148; https://doi.org/10.3390/atmos9040148 - 16 Apr 2018

Viewed by 2669

Abstract

The authors would like to correct the published article [1], following the detection of editorial mistakes by the main author, as explained below[...] Full article

(This article belongs to the Special Issue Precipitation Variability and Change in Africa)

3 pages, 4576 KiB

Open AccessEditorial

Announcing the Atmosphere 2018 Travel Award for Young Investigators

by Atmosphere Editorial Office

Atmosphere 2018, 9(4), 147; https://doi.org/10.3390/atmos9040147 - 16 Apr 2018

Viewed by 3832

Abstract

n/a Full article

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23 pages, 17758 KiB

Open AccessArticle

Accounting for Field-Scale Dry Deposition in Backward Lagrangian Stochastic Dispersion Modelling of NH₃ Emissions

by Christoph Häni, Christophe Flechard, Albrecht Neftel, Jörg Sintermann and Thomas Kupper

Atmosphere 2018, 9(4), 146; https://doi.org/10.3390/atmos9040146 - 14 Apr 2018

Cited by 20 | Viewed by 4684

Abstract

A controlled ammonia (NH₃) release experiment was performed at a grassland site. The aim was to quantify the effect of dry deposition between the source and the receptors (NH₃ measurement locations) on emission rate estimates by means of inverse dispersion [...] Read more.

A controlled ammonia (NH₃) release experiment was performed at a grassland site. The aim was to quantify the effect of dry deposition between the source and the receptors (NH₃ measurement locations) on emission rate estimates by means of inverse dispersion modelling. NH₃ was released for three hours at a constant rate of

Q

= 6.29 mg s⁻¹ from a grid of 36 orifices spread over an area of 250 m². The increase in line-integrated NH₃ concentration was measured with open-path optical miniDOAS devices at different locations downwind of the artificial source. Using a backward Lagrangian stochastic (bLS) dispersion model (bLSmodelR), the fraction of the modelled release rate to the emitted NH₃ (

Q_{bLS} / Q

) was calculated from the measurements of the individual instruments.

Q_{bLS} / Q

was found to be systematically lower than 1, on average between 0.69 and 0.91, depending on the location of the receptor. We hypothesized that NH₃ dry deposition to grass and soil surfaces was the main factor responsible for the observed depletion of NH₃ between source and receptor. A dry deposition algorithm based on a deposition velocity approach was included in the bLS modelling. Model deposition velocities were evaluated from a ‘big-leaf’ canopy resistance analogy. Canopy resistances (generally termed

R_{c}

) that provided

Q_{bLS} / Q

= 1 ranged from 75 to 290 s m⁻¹, showing that surface removal of NH₃ by dry deposition can plausibly explain the original underestimation of

Q_{bLS} / Q

. The inclusion of a dry deposition process in dispersion modelling is crucial for emission estimates, which are based on concentration measurements of depositing tracers downwind of homogeneous area sources or heterogeneously-distributed hot spots, such as, e.g., urine patches on pastures in the case of NH₃. Full article

(This article belongs to the Special Issue Micrometeorological Studies of Greenhouse Gas Fluxes from Agricultural Operations)

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20 pages, 17800 KiB

Open AccessArticle

Air-Pollutant Emissions from Agricultural Burning in Mae Chaem Basin, Chiang Mai Province, Thailand

by Noppol Arunrat, Nathsuda Pumijumnong and Sukanya Sereenonchai

Atmosphere 2018, 9(4), 145; https://doi.org/10.3390/atmos9040145 - 13 Apr 2018

Cited by 39 | Viewed by 10040

Abstract

Particulate pollution is a continual problem which is usually caused by the burning of crop residues in highland agricultural systems. The objectives of this study are to investigate crop-residue management and estimate the amount of pollutant emissions from burning crop residues for each [...] Read more.

Particulate pollution is a continual problem which is usually caused by the burning of crop residues in highland agricultural systems. The objectives of this study are to investigate crop-residue management and estimate the amount of pollutant emissions from burning crop residues for each land-use pattern (grain maize, seed maize and integrated farming), and to estimate the chemical compositions of PM_2.5 emissions from agricultural burning in Mae Chaem basin, Chiang Mai Province, Thailand. The purposive sampling method was used for sample selection. A door-to-door questionnaire survey was used to obtain responses from 149 respondents. Greenhouse gas (GHG) emissions from the open burning of crop residues were estimated, using specific emission factors obtained from several literature reviews and from the field by the questionnaire survey. Results revealed that the majority of farmers burned maize residues during April and May and mostly in the afternoon. These burning behaviors are in line with the supportive weather conditions that reflect high values of temperature and wind speed, and less rainfall and relative humidity result in maize residues being burned easily and quickly. The integrated farming system generated the lowest GHG emissions and amount of chemical composition of PM_2.5 emissions, followed by the grain maize and seed maize patterns, respectively. This study strongly supports the implementation of the integrated farming system in Mae Chaem basin. Proactive and reactive measures should be taken in a well-organized and systematic fashion and should engage all related parties. More importantly, there is an urgent need for policy makers to include PM_2.5 concentrations to upgrade Thailand’s air-quality index (PM_2.5 AQI). Full article

(This article belongs to the Special Issue Fire and the Atmosphere)

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18 pages, 9475 KiB

Open AccessArticle

Hazard Quotients, Hazard Indexes, and Cancer Risks of Toxic Metals in PM₁₀ during Firework Displays

by Siwatt Pongpiachan, Akihiro Iijima and Junji Cao

Atmosphere 2018, 9(4), 144; https://doi.org/10.3390/atmos9040144 - 12 Apr 2018

Cited by 36 | Viewed by 7983

Abstract

Bonfire night is a worldwide phenomenon given to numerous annual celebrations characterised by bonfires and fireworks. Since Thailand has no national ambient air quality standards for metal particulates, it is important to investigate the impacts of particulate injections on elevations of air pollutants [...] Read more.

Bonfire night is a worldwide phenomenon given to numerous annual celebrations characterised by bonfires and fireworks. Since Thailand has no national ambient air quality standards for metal particulates, it is important to investigate the impacts of particulate injections on elevations of air pollutants and the ecological health impacts resulting from firework displays. In this investigation, Pb and Ba were considered potential firework tracers because their concentrations were significantly higher during the episode, and lower than/comparable with minimum detection limits during other periods, indicating that their elevated concentrations were principally due to pyrotechnic displays. Pb/Ca, Pb/Al, Pb/Mg, and Pb/Cu can be used to pin-point emissions from firework displays. Air mass backward trajectories (72 h) from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicated that areas east and north-east of the study site were the main sources of the airborne particles. Although the combined risk associated with levels of Pb, Cr, Co., Ni, Zn, As, Cd, V, and Mn was far below the standards mentioned in international guidelines, the lifetime cancer risks associated with As and Cr levels exceeded US-EPA guidelines, and may expose inhabitants of surrounding areas of Bangkok to an elevated cancer risk. Full article

(This article belongs to the Special Issue Urban Particulate Matters: Composition, Sources, and Exposure)

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9 pages, 4148 KiB

Open AccessArticle

Observed Correlation between Aerosol and Cloud Base Height for Low Clouds at Baltimore and New York, United States

by Sium Gebremariam, Siwei Li and Mengsteab Weldegaber

Atmosphere 2018, 9(4), 143; https://doi.org/10.3390/atmos9040143 - 11 Apr 2018

Cited by 11 | Viewed by 4978

Abstract

The correlation between aerosol particulate matter with aerodynamic diameter ≤2.5

μ m

(PM_2.5) and cloud base height (CBH) of low clouds (CBH lower than 1.5 km a.g.l.) at Baltimore and New York, United States, for an 8 year period (2007–2014) was [...] Read more.

The correlation between aerosol particulate matter with aerodynamic diameter ≤2.5

μ m

(PM_2.5) and cloud base height (CBH) of low clouds (CBH lower than 1.5 km a.g.l.) at Baltimore and New York, United States, for an 8 year period (2007–2014) was investigated using information from the Automated Surface Observing System (ASOS) observations and collocated U.S. Environmental Protection Agency (EPA) observations. The lifting condensation level (LCL) heights were calculated and compared with the CBH. The monthly average observations show that PM_2.5 decreases from 2007 to 2014 while there is no significant trend found for CBH and LCL. The variability of the LCL height agrees well with CBH but LCL height is systematically lower than CBH (~180 m lower). There was a significant negative correlation found between CBH–LCL and PM_2.5. All of the cloud cases were separated into polluted and clean conditions based on the distribution of PM_2.5 values. The distributions of CBH–LCL in the two groups show more cloud cases with smaller CBH–LCL in polluted conditions than in clean conditions. Full article

(This article belongs to the Special Issue Atmospheric Aerosol Composition and its Impact on Clouds)

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17 pages, 21329 KiB

Open AccessArticle

Oasis Irrigation-Induced Hydro-Climatic Effects: A Case Study in the Hyper-Arid Region of Northwest China

by Nan Shan, Zhongjie Shi, Xiaohui Yang, Hao Guo, Xiao Zhang and Zhiyong Zhang

Atmosphere 2018, 9(4), 142; https://doi.org/10.3390/atmos9040142 - 10 Apr 2018

Cited by 5 | Viewed by 3591

Abstract

The response of potential evapotranspiration (ET0) to widespread irrigation is important to fully understand future regional climate changes and to infer adaptive management of agricultural water resources. The quantitative impact of irrigation on ET0 from 1960 to 2013 was evaluated using historical time [...] Read more.

The response of potential evapotranspiration (ET0) to widespread irrigation is important to fully understand future regional climate changes and to infer adaptive management of agricultural water resources. The quantitative impact of irrigation on ET0 from 1960 to 2013 was evaluated using historical time series data of daily meteorological observations in the hyper-arid region of northwest China. The decreasing trends in ET0 were accelerated for meteorological stations in regions with oasis agriculture, especially in the summer and during the growing season. Irrigation led to a cooling effect on temperature, increased relative humidity and precipitation. All of these changes contributed to a larger decrease of ET0 trend. The findings of this study advance our insight into the effects of irrigation on dynamics in ET0 and meteorological factors. Further investigations to understand how ET0 responds to climate change and agricultural irrigation could provide guidance for determining effective measures of water resources for adapting to global change. Full article

(This article belongs to the Section Biosphere/Hydrosphere/Land–Atmosphere Interactions)

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21 pages, 41713 KiB

Open AccessArticle

Regional Forecasting of Wind Speeds during Typhoon Landfall in Taiwan: A Case Study of Westward-Moving Typhoons

by Chih-Chiang Wei, Po-Chun Peng, Cheng-Han Tsai and Chien-Lin Huang

Atmosphere 2018, 9(4), 141; https://doi.org/10.3390/atmos9040141 - 10 Apr 2018

Cited by 10 | Viewed by 5381

Abstract

Taiwan is located on a route where typhoons often strike. Each year, the strong winds accompanying typhoons are a substantial threat and cause significant damage. However, because the terrains of high mountains in Taiwan vary greatly, when a typhoon passes the Central Mountain [...] Read more.

Taiwan is located on a route where typhoons often strike. Each year, the strong winds accompanying typhoons are a substantial threat and cause significant damage. However, because the terrains of high mountains in Taiwan vary greatly, when a typhoon passes the Central Mountain Range (CMR), the wind speed of typhoons becomes difficult to predict. This research had two primary objectives: (1) to develop data-driven techniques and a powerful artificial neural network (ANN) model to predict the highly complex nonlinear wind systems in western Taiwan; and, (2) to investigate the accuracy of wind speed predictions at various locations and for various durations in western Taiwan when the track of westward typhoons is affected by the complex geographical shelters and disturbances of the CMR. This study developed a typhoon wind speed prediction model that evaluated various typhoon tracks (covering Type 2, Type 3, and Type 4 tracks, as defined by the Central Weather Bureau), and evaluated the prediction accuracy at Hsinchu, Wuqi, and Kaohsiung Stations in western Taiwan. Back propagation neural networks (BPNNs) were employed to establish wind speed prediction models, and a linear regression model was adopted as the benchmark to evaluate the strengths and weaknesses of the BPNNs. The results were as follows: (1) The BPNNs generally had favorable performance in predicting wind speeds and their performances were superior to linear regressions; (2) when absolute errors were adopted to evaluate the prediction performances, the predictions at Hsinchu Station were the most accurate, whereas those at Wuqi Station were the least accurate; however, when relative errors were adopted, the predictions at Hsinchu Station were again the most accurate, whereas those at Kaohsiung were the least accurate; and, (3) regarding the relative error rates for the maximum wind speed of Types 2, 3, and 4 typhoons, Wuqi, Kaohsiung, and Wuqi had the most accurate performance, respectively; as for maximum wind time error (ET_M) for Types 2, 3, and 4 typhoons, Kaohsiung, Wuqi, and Wuqi correspondingly performed the most favorably. Full article

(This article belongs to the Special Issue Tropical Cyclones and Their Impacts)

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14 pages, 9337 KiB

Open AccessArticle

Freezing on a Chip—A New Approach to Determine Heterogeneous Ice Nucleation of Micrometer-Sized Water Droplets

by Thomas Häusler, Lorenz Witek, Laura Felgitsch, Regina Hitzenberger and Hinrich Grothe

Atmosphere 2018, 9(4), 140; https://doi.org/10.3390/atmos9040140 - 10 Apr 2018

Cited by 20 | Viewed by 6038

Abstract

We are presenting a new approach to analyze the freezing behavior of aqueous droplets containing ice nucleating particles. The freezing chip consists of an etched and sputtered (15 × 15 × 1) mm gold-plated silicon or pure gold chip, enabling the formation of [...] Read more.

We are presenting a new approach to analyze the freezing behavior of aqueous droplets containing ice nucleating particles. The freezing chip consists of an etched and sputtered (15 × 15 × 1) mm gold-plated silicon or pure gold chip, enabling the formation of droplets with defined diameters between 20 and 80 µm. Several applications like an automated process control and an automated image evaluation were implemented to improve the quality of heterogeneous freezing experiments. To show the functionality of the setup, we compared freezing temperatures of aqueous droplets containing ice nucleating particles (i.e., microcline, birch pollen washing water, juniper pollen, and Snomax^® solution) measured with our setup, with literature data. The ice nucleation active surface/mass site density (n_s/m) of microcline, juniper pollen, and birch pollen washing water are shown to be in good agreement with literature data. Minor variations can be explained by slight differences in composition and droplet generation technique. The n_m values of Snomax^® differ by up to one order of magnitude at higher subzero temperatures when compared with fresh samples but are in agreement when compared with reported data of aged Snomax^® samples. Full article

(This article belongs to the Special Issue Ice Nucleation in the Atmosphere)

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7 pages, 809 KiB

Open AccessCommunication

A Technique for Estimating Greenhouse Gas Exchange Adjacent Cattle Feedlots

by Sean M. McGinn and Thomas K. Flesch

Atmosphere 2018, 9(4), 139; https://doi.org/10.3390/atmos9040139 - 9 Apr 2018

Cited by 1 | Viewed by 4107

Abstract

Concentrated animal feeding operations (CAFO) such as open-air beef cattle feedlots are known ‘hot spots’ of emissions of numerous gases including the major greenhouse gases methane, nitrous oxide, and carbon dioxide. Some work has documented CAFOs to derive typical emission factors, but few [...] Read more.

Concentrated animal feeding operations (CAFO) such as open-air beef cattle feedlots are known ‘hot spots’ of emissions of numerous gases including the major greenhouse gases methane, nitrous oxide, and carbon dioxide. Some work has documented CAFOs to derive typical emission factors, but few studies have looked beyond the CAFO to the local landscape to derive the net off-farm emissions. To address the net emissions, the exchange of gases downwind of CAFOs is required, determined in part by the air quality of the gas plume from the CAFO and the characteristics of the underlying surface. Our study measured these downwind fluxes at an open-air beef cattle feedlot using an open-path Fourier Transform Infrared detector and a flux-gradient method. The results showed the dynamic response of fluxes to gas concentration (fresh air or feedlot air) and surface condition (actively growing crop and tilled stubble). These results shed light on the pathways of greenhouse gas flow near a CAFO source, and showed that solely measuring source emissions from a CAFO would lead to errors when developing emission factors. Full article

(This article belongs to the Special Issue Micrometeorological Studies of Greenhouse Gas Fluxes from Agricultural Operations)

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14 pages, 37660 KiB

Open AccessArticle

The Global Precipitation Climatology Project (GPCP) Monthly Analysis (New Version 2.3) and a Review of 2017 Global Precipitation

by Robert F. Adler, Mathew R. P. Sapiano, George J. Huffman, Jian-Jian Wang, Guojun Gu, David Bolvin, Long Chiu, Udo Schneider, Andreas Becker, Eric Nelkin, Pingping Xie, Ralph Ferraro and Dong-Bin Shin

Atmosphere 2018, 9(4), 138; https://doi.org/10.3390/atmos9040138 - 7 Apr 2018

Cited by 604 | Viewed by 24708

Abstract

The new Version 2.3 of the Global Precipitation Climatology Project (GPCP) Monthly analysis is described in terms of changes made to improve the homogeneity of the product, especially after 2002. These changes include corrections to cross-calibration of satellite data inputs and updates to [...] Read more.

The new Version 2.3 of the Global Precipitation Climatology Project (GPCP) Monthly analysis is described in terms of changes made to improve the homogeneity of the product, especially after 2002. These changes include corrections to cross-calibration of satellite data inputs and updates to the gauge analysis. Over-ocean changes starting in 2003 resulted in an overall precipitation increase of 1.8% after 2009. Updating the gauge analysis to its final, high-quality version increases the global land total by 1.8% for the post-2002 period. These changes correct a small, incorrect dip in the estimated global precipitation over the last decade given by the earlier Version 2.2. The GPCP analysis is also used to describe global precipitation in 2017. The general La Niña pattern for 2017 is noted and the evolution from the early 2016 El Niño pattern is described. The 2017 global value is one of the highest for the 1979–2017 period, exceeded only by 2016 and 1998 (both El Niño years), and reinforces the small positive trend. Results for 2017 also reinforce significant trends in precipitation intensity (on a monthly scale) in the tropics. These results for 2017 indicate the value of the GPCP analysis, in addition to research, for climate monitoring. Full article

(This article belongs to the Section Meteorology)

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21 pages, 19571 KiB

Open AccessArticle

Atmospheric Distribution of PAHs and Quinones in the Gas and PM₁ Phases in the Guadalajara Metropolitan Area, Mexico: Sources and Health Risk

by Valeria Ojeda-Castillo, Alberto López-López, Leonel Hernández-Mena, Mario Alfonso Murillo-Tovar, José De Jesús Díaz-Torres, Iván Y. Hernández-Paniagua, Jorge Del Real-Olvera and Elizabeth León-Becerril

Atmosphere 2018, 9(4), 137; https://doi.org/10.3390/atmos9040137 - 5 Apr 2018

Cited by 9 | Viewed by 5598

Abstract

Polycyclic aromatic hydrocarbons (PAHs) and quinones in the gas phase and as submicron particles raise concerns due to their potentially carcinogenic and mutagenic properties. The majority of existing studies have investigated the formation of quinones, but it is also important to consider both [...] Read more.

Polycyclic aromatic hydrocarbons (PAHs) and quinones in the gas phase and as submicron particles raise concerns due to their potentially carcinogenic and mutagenic properties. The majority of existing studies have investigated the formation of quinones, but it is also important to consider both the primary and secondary sources to estimate their contributions. The objectives of this study were to characterize PAHs and quinones in the gas and particulate matter (PM₁) phases in order to identify phase distributions, sources, and cancer risk at two urban monitoring sites in the Guadalajara Metropolitan Area (GMA) in Mexico. The simultaneous gas and PM₁ phases samples were analyzed using a gas chromatography–mass spectrometer. The lifetime lung cancer risk (LCR) due to PAH exposure was calculated to be 1.7 × 10⁻³, higher than the recommended risk value of 10⁻⁶, indicating a potential health hazard. Correlations between parent PAHs, criteria pollutants, and meteorological parameters suggest that primary sources are the main contributors to the Σ₈ Quinones concentrations in PM₁, while the secondary formation of 5,12-naphthacenequinone and 9,10-anthraquinone may contribute less to the observed concentration of quinones. Additionally, naphthalene, acenaphthene, fluorene, phenanthrene, and anthracene in PM₁, suggest photochemical degradation into unidentified species. Further research is needed to determine how these compounds are formed. Full article

(This article belongs to the Special Issue Urban Particulate Matters: Composition, Sources, and Exposure)

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16 pages, 7253 KiB

Open AccessArticle

Enhanced Global Monsoon in Present Warm Period Due to Natural and Anthropogenic Forcings

by Jing Chai, Fei Liu, Jian Liu and Xinyong Shen

Atmosphere 2018, 9(4), 136; https://doi.org/10.3390/atmos9040136 - 4 Apr 2018

Cited by 4 | Viewed by 4241

Abstract

In this study, we investigate global monsoon precipitation (GMP) changes between the Present Warm Period (PWP, 1900–2000) and the Little Ice Age (LIA, 1250–1850) by performing millennium sensitivity simulations using the Community Earth System Model version 1.0 (CESM1). Three millennium simulations are carried [...] Read more.

In this study, we investigate global monsoon precipitation (GMP) changes between the Present Warm Period (PWP, 1900–2000) and the Little Ice Age (LIA, 1250–1850) by performing millennium sensitivity simulations using the Community Earth System Model version 1.0 (CESM1). Three millennium simulations are carried out under time-varying solar, volcanic and greenhouse gas (GHG) forcing, respectively, from 501 to 2000 AD. Compared to the global-mean surface temperature of the cold LIA, the global warming in the PWP caused by high GHG concentration is about 0.42 °C, by strong solar radiation is 0.14 °C, and by decreased volcanic activity is 0.07 °C. The GMP increases in these three types of global warming are comparable, being 0.12, 0.058, and 0.055 mm day⁻¹, respectively. For one degree of global warming, the GMP increase induced by strong GHG forcing is 2.2% °C⁻¹, by strong solar radiation is 2.8% °C⁻¹, and by decreased volcanic forcing is 5.5% °C⁻¹, which means that volcanic forcing is most effective in terms of changing the GMP among these three external forcing factors. Under volcanic inactivity-related global warming, both monsoon moisture and circulation are enhanced, and the enhanced circulation mainly occurs in the Northern Hemisphere (NH). The circulation, however, is weakened in the other two cases, and the GMP intensification is mainly caused by increased moisture. Due to large NH volcanic aerosol concentration in the LIA, the inter-hemispheric thermal contrast of PWP global warming tends to enhance NH monsoon circulation. Compared to the GHG forcing, solar radiation tends to warm low-latitude regions and cause a greater monsoon moisture increase, resulting in a stronger GMP increase. The finding in this study is important for predicting the GMP in future anthropogenic global warming when a change in natural solar or volcanic activity occurs. Full article

(This article belongs to the Section Meteorology)

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19 pages, 23071 KiB

Open AccessArticle

Statistical Analysis of Spatiotemporal Heterogeneity of the Distribution of Air Quality and Dominant Air Pollutants and the Effect Factors in Qingdao Urban Zones

by Xiangwei Zhao, Qian Gao, Meng Sun, Yunchuan Xue, RuiJin Ma, Xingyuan Xiao and Bo Ai

Atmosphere 2018, 9(4), 135; https://doi.org/10.3390/atmos9040135 - 4 Apr 2018

Cited by 11 | Viewed by 8445

Abstract

Air pollution has impacted people’s lives in urban China, and the analysis of the distribution and driving factors behind air quality has become a current research focus. In this study, the temporal heterogeneity of air quality (AQ) and the dominant air pollutants across [...] Read more.

Air pollution has impacted people’s lives in urban China, and the analysis of the distribution and driving factors behind air quality has become a current research focus. In this study, the temporal heterogeneity of air quality (AQ) and the dominant air pollutants across the four seasons were analyzed based on the Kruskal-Wallis rank-sum test method. Then, the spatial heterogeneity of AQ and the dominant air pollutants across four sites were analyzed based on the Wilcoxon signed-rank test method. Finally, the copula model was introduced to analyze the effect of relative factors on dominant air pollutants. The results show that AQ and dominant air pollutants present significant spatiotemporal heterogeneity in the study area. AQ is worst in winter and best in summer. PM₁₀, O₃, and PM_2.5 are the dominant air pollutants in spring, summer, and winter, respectively. The average concentration of dominant air pollutants presents significant and diverse daily peaks and troughs across the four sites. The main driving factors are pollutants such as SO₂, NO₂, and CO, so pollutant emission reduction is the key to improving air quality. Corresponding pollution control measures should account for this heterogeneity in terms of AQ and the dominant air pollutants among different urban zones. Full article

(This article belongs to the Section Air Quality)

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19 pages, 1038 KiB

Open AccessReview

Land-Use Regression Modelling of Intra-Urban Air Pollution Variation in China: Current Status and Future Needs

by Baihuiqian He, Mathew R. Heal and Stefan Reis

Atmosphere 2018, 9(4), 134; https://doi.org/10.3390/atmos9040134 - 3 Apr 2018

Cited by 31 | Viewed by 7952

Abstract

Rapid urbanization in China is leading to substantial adverse air quality issues, particularly for NO₂ and particulate matter (PM). Land-use regression (LUR) models are now being applied to simulate pollutant concentrations with high spatial resolution in Chinese urban areas. However, Chinese urban [...] Read more.

Rapid urbanization in China is leading to substantial adverse air quality issues, particularly for NO₂ and particulate matter (PM). Land-use regression (LUR) models are now being applied to simulate pollutant concentrations with high spatial resolution in Chinese urban areas. However, Chinese urban areas differ from those in Europe and North America, for example in respect of population density, urban morphology and pollutant emissions densities, so it is timely to assess current LUR studies in China to highlight current challenges and identify future needs. Details of twenty-four recent LUR models for NO₂ and PM_2.5/PM₁₀ (particles with aerodynamic diameters <2.5 µm and <10 µm) are tabulated and reviewed as the basis for discussion in this paper. We highlight that LUR modelling in China is currently constrained by a scarcity of input data, especially air pollution monitoring data. There is an urgent need for accessible archives of quality-assured measurement data and for higher spatial resolution proxy data for urban emissions, particularly in respect of traffic-related variables. The rapidly evolving nature of the Chinese urban landscape makes maintaining up-to-date land-use and urban morphology datasets a challenge. We also highlight the importance for Chinese LUR models to be subject to appropriate validation statistics. Integration of LUR with portable monitor data, remote sensing, and dispersion modelling has the potential to enhance derivation of urban pollution maps. Full article

(This article belongs to the Section Air Quality)

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18 pages, 19266 KiB

Open AccessArticle

Seasonal Variability of Airborne Particulate Matter and Bacterial Concentrations in Colorado Homes

by Nicholas Clements, Patricia Keady, Joanne B. Emerson, Noah Fierer and Shelly L. Miller

Atmosphere 2018, 9(4), 133; https://doi.org/10.3390/atmos9040133 - 2 Apr 2018

Cited by 20 | Viewed by 7728

Abstract

Aerosol measurements were collected at fifteen homes over the course of one year in Colorado (USA) to understand the temporal variability of indoor air particulate matter and bacterial concentrations and their relationship with home characteristics, inhabitant activities, and outdoor air particulate matter (PM). [...] Read more.

Aerosol measurements were collected at fifteen homes over the course of one year in Colorado (USA) to understand the temporal variability of indoor air particulate matter and bacterial concentrations and their relationship with home characteristics, inhabitant activities, and outdoor air particulate matter (PM). Indoor and outdoor PM_2.5 concentrations averaged (±st. dev.) 8.1 ± 8.1 μg/m³ and 6.8 ± 4.5 μg/m³, respectively. Indoor PM_2.5 was statistically significantly higher during summer compared to spring and winter; outdoor PM_2.5 was significantly higher for summer compared to spring and fall. The PM_2.5 I/O ratio was 1.6 ± 2.4 averaged across all homes and seasons and was not statistically significantly different across the seasons. Average indoor PM₁₀ was 15.4 ± 18.3 μg/m³ and was significantly higher during summer compared to all other seasons. Total suspended particulate bacterial biomass, as determined by qPCR, revealed very little seasonal differences across and within the homes. The qPCR I/O ratio was statistically different across seasons, with the highest I/O ratio in the spring and lowest in the summer. Using one-minute indoor PM₁₀ data and activity logs, it was observed that elevated particulate concentrations commonly occurred when inhabitants were cooking and during periods with elevated outdoor concentrations. Full article

(This article belongs to the Special Issue Indoor Air Pollution)

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17 pages, 17495 KiB

Open AccessEditor’s ChoiceArticle

Refinement of Modeled Aqueous-Phase Sulfate Production via the Fe- and Mn-Catalyzed Oxidation Pathway

by Syuichi Itahashi, Kazuyo Yamaji, Satoru Chatani and Hiroshi Hayami

Atmosphere 2018, 9(4), 132; https://doi.org/10.3390/atmos9040132 - 1 Apr 2018

Cited by 23 | Viewed by 5899

Abstract

We refined the aqueous-phase sulfate (SO₄²⁻) production in the state-of-the-art Community Multiscale Air Quality (CMAQ) model during the Japanese model inter-comparison project, known as Japan’s Study for Reference Air Quality Modeling (J-STREAM). In Japan, SO₄²⁻ is the major [...] Read more.

We refined the aqueous-phase sulfate (SO₄²⁻) production in the state-of-the-art Community Multiscale Air Quality (CMAQ) model during the Japanese model inter-comparison project, known as Japan’s Study for Reference Air Quality Modeling (J-STREAM). In Japan, SO₄²⁻ is the major component of PM_2.5, and CMAQ reproduces the observed seasonal variation of SO₄²⁻ with the summer maxima and winter minima. However, CMAQ underestimates the concentration during winter over Japan. Based on a review of the current modeling system, we identified a possible reason as being the inadequate aqueous-phase SO₄²⁻ production by Fe- and Mn-catalyzed O₂ oxidation. This is because these trace metals are not properly included in the Asian emission inventories. Fe and Mn observations over Japan showed that the model concentrations based on the latest Japanese emission inventory were substantially underestimated. Thus, we conducted sensitivity simulations where the modeled Fe and Mn concentrations were adjusted to the observed levels, the Fe and Mn solubilities were increased, and the oxidation rate constant was revised. Adjusting the concentration increased the SO₄²⁻ concentration during winter, as did increasing the solubilities and revising the rate constant to consider pH dependencies. Statistical analysis showed that these sensitivity simulations improved model performance. The approach adopted in this study can partly improve model performance in terms of the underestimation of SO₄²⁻ concentration during winter. From our findings, we demonstrated the importance of developing and evaluating trace metal emission inventories in Asia. Full article

(This article belongs to the Special Issue Regional Scale Air Quality Modelling)

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14 pages, 3295 KiB

Open AccessArticle

The Influence of Absolute Mass Loading of Secondary Organic Aerosols on Their Phase State

by Shashank Jain, Kevin B. Fischer and Giuseppe A. Petrucci

Atmosphere 2018, 9(4), 131; https://doi.org/10.3390/atmos9040131 - 31 Mar 2018

Cited by 14 | Viewed by 5488 | Correction

Abstract

Absolute secondary organic aerosol (SOA) mass loading (C_SOA) is a key parameter in determining partitioning of semi- and intermediate volatility compounds to the particle phase. Its impact on the phase state of SOA, however, has remained largely unexplored. In this study, [...] Read more.

Absolute secondary organic aerosol (SOA) mass loading (C_SOA) is a key parameter in determining partitioning of semi- and intermediate volatility compounds to the particle phase. Its impact on the phase state of SOA, however, has remained largely unexplored. In this study, systematic laboratory chamber measurements were performed to elucidate the influence of C_SOA, ranging from 0.2 to 160 µg m⁻³, on the phase state of SOA formed by ozonolysis of various precursors, including α-pinene, limonene, cis-3-hexenyl acetate (CHA) and cis-3-hexen-1-ol (HXL). A previously established method to estimate SOA bounce factor (BF, a surrogate for particle viscosity) was utilized to infer particle viscosity as a function of C_SOA. Results show that under nominally identical conditions, the maximum BF decreases by approximately 30% at higher C_SOA, suggesting a more liquid phase state. With the exception of HXL-SOA (which acted as the negative control), the phase state for all studied SOA precursors varied as a function of C_SOA. Furthermore, the BF was found to be the maximum when SOA particle distributions reached a geometric mean particle diameter of 50–60 nm. Experimental results indicate that C_SOA is an important parameter impacting the phase state of SOA, reinforcing recent findings that extrapolation of experiments not conducted at atmospherically relevant SOA levels may not yield results that are relevant to the natural environment. Full article

(This article belongs to the Special Issue Formation and Transformation of Organic Aerosol)

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27 pages, 3837 KiB

Open AccessReview

A Review of Paleo El Niño-Southern Oscillation

by Zhengyao Lu, Zhengyu Liu, Jiang Zhu and Kim M. Cobb

Atmosphere 2018, 9(4), 130; https://doi.org/10.3390/atmos9040130 - 30 Mar 2018

Cited by 52 | Viewed by 11760

Abstract

The Earth has seen El Niño-Southern Oscillation (ENSO)—the leading mode of interannual climate variability—for at least millennia and likely over millions of years. This paper reviews previous studies from perspectives of both paleoclimate proxy data (from traditional sediment records to the latest high-resolution [...] Read more.

The Earth has seen El Niño-Southern Oscillation (ENSO)—the leading mode of interannual climate variability—for at least millennia and likely over millions of years. This paper reviews previous studies from perspectives of both paleoclimate proxy data (from traditional sediment records to the latest high-resolution oxygen isotope records) and model simulations (including earlier intermediate models to the latest isotope-enabled coupled models). It summarizes current understanding of ENSO’s past evolution during both interglacial and glacial periods and its response to external climatic forcings such as volcanic, orbital, ice-sheet and greenhouse gas forcings. Due to the intrinsic irregularity of ENSO and its complicated relationship with other climate phenomena, reconstructions and model simulations of ENSO variability are subject to inherent difficulties in interpretations and biases. Resolving these challenges through new data syntheses, new statistical methods, more complex climate model simulations as well as direct model-data comparisons can potentially better constrain uncertainty regarding ENSO’s response to future global warming. Full article

(This article belongs to the Special Issue El Niño Southern Oscillation (ENSO))

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20 pages, 21564 KiB

Open AccessArticle

Temperature Extremes: Estimation of Non-Stationary Return Levels and Associated Uncertainties

by Yasser Hamdi, Claire-Marie Duluc and Vincent Rebour

Atmosphere 2018, 9(4), 129; https://doi.org/10.3390/atmos9040129 - 29 Mar 2018

Cited by 15 | Viewed by 5188

Abstract

Estimating temperature extremes (TEs) and associated uncertainties under the non-stationary (NS) assumption is a key research question in several domains, including the nuclear safety field. Methods for estimating TEs and associated confidence intervals (CIs) have often been used in the literature but in [...] Read more.

Estimating temperature extremes (TEs) and associated uncertainties under the non-stationary (NS) assumption is a key research question in several domains, including the nuclear safety field. Methods for estimating TEs and associated confidence intervals (CIs) have often been used in the literature but in a stationary context, separately and without detailed comparison. The extreme value theory is often used to assess risks in a context of climate change. It provides an accurate indication of distributions describing the frequency of occurrence of TEs. However, in an NS context, the notion of the return period is not easily interpretable. For instance, to predict a high return level (RL) in a future year, time-varying distributions must be used and compared. This study examines the performance of a new concept to predict RLs in an NS context and compares three methods for constructing the associated CIs (delta, profile likelihood, and parametric bootstrap). The present work takes up the concept of integrated return periods that define the T-year RL as the level for which the expected number of events in a T-year period is one and proposes a new method based on conditional predictions that is useful for predicting high RLs of extreme events in the near future (the 100-year RL in the year 2030, for instance). The daily maximum temperature (DMT) observed at the Orange Station in France was used as a case study. Several trend models were compared and a new likelihood-based method to detect breaks in TEs is proposed. The analyses were conducted assuming the time-varying Generalized Extreme Value (GEV) distribution. The concepts have been implemented in a software package (Non-Stationary Generalized Extreme Value (NSGEV)). The application demonstrates that the RL estimates for NS situations can be quite different from those corresponding to stationary conditions. Overall, the results suggest that the NS analysis can be helpful in making a more appropriate assessment of the risk for periodic safety reviews during the life of a nuclear power plant (NPP). Full article

(This article belongs to the Special Issue Temperature Extremes and Heat/Cold Waves)

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13 pages, 15861 KiB

Open AccessArticle

Micrometeorological Measurements Reveal Large Nitrous Oxide Losses during Spring Thaw in Alberta

by Thomas K. Flesch, Vern S. Baron, John D. Wilson, John A. Basarab, Raymond L. Desjardins, Devon Worth and Reynald L. Lemke

Atmosphere 2018, 9(4), 128; https://doi.org/10.3390/atmos9040128 - 29 Mar 2018

Cited by 22 | Viewed by 3766

Abstract

Agricultural soils in Canada have been observed to emit a large pulse of nitrous oxide (N₂O) gas during the spring thaw, representing a large percentage of the annual emissions. We report on three years of spring thaw N₂O flux [...] Read more.

Agricultural soils in Canada have been observed to emit a large pulse of nitrous oxide (N₂O) gas during the spring thaw, representing a large percentage of the annual emissions. We report on three years of spring thaw N₂O flux measurements taken at three Alberta agricultural sites: a crop production site (Crop), cattle winter-feeding site (WF), and a cattle winter-grazing site (WG). Soil fluxes were calculated with a micrometeorological technique based on the vertical gradient in N₂O concentration above each site measured with an open-path (line-averaging) FTIR gas detector. The Crop and WG sites showed a clear N₂O emission pulse lasting 10 to 25 days after thawing began. During this pulse there was a strong diurnal cycle in emissions that paralleled the cycle in near-surface soil temperature. The emission pulse was less pronounced at the WF site. The average spring thaw losses (over 25 to 31 days) were 5.3 (Crop), 7.0 (WF), and 8.0 (WG) kg N₂O-N ha⁻¹, representing 1 to 3.5% of the annual nitrogen input to the sites. These large losses are higher than found in most previous western Canadian studies, and generally higher than the annual losses estimated from the Intergovernmental Panel on Climate Change and Canadian National Inventory Report calculations. The high N₂O losses may be explained by high soil nitrate levels which promoted rapid denitrification during thawing. The application of a high resolution (temporal) micrometeorological technique was critical to revealing these losses. Full article

(This article belongs to the Special Issue Micrometeorological Studies of Greenhouse Gas Fluxes from Agricultural Operations)

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