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Volume 8
Issue 4
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Atmosphere, Volume 8, Issue 4 (April 2017) – 16 articles

Cover Story (view full-size image): A special and unusual purple (magenta) haze episode was observed in Nanjing, China, at 17:00 on 22 December 2015. Many local and national news outlets reported on this event. One explanation of how a purple (combination of blue and red) light could be created is by green wavelengths being absorbed. Another way involves pollution gases or particles together with small liquid/water droplets, but this still needs further clarification. A third possibility is that the combination of transmitted red light from the sun and scattered blue light could produce a purple/magenta color in the sky. By Duanyang Liu. View this paper.
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9836 KiB  
Article
Application of Convective Condensation Level Limiter in Convective Boundary Layer Height Retrieval Based on Lidar Data
by Hong Li, Yi Yang, Xiao-Ming Hu, Zhongwei Huang, Guoyin Wang and Beidou Zhang
Atmosphere 2017, 8(4), 79; https://doi.org/10.3390/atmos8040079 - 23 Apr 2017
Cited by 11 | Viewed by 6326
Abstract
Micro pulse lidar is a promising tool for retrieving the convective boundary layer height (CBLH), but its application has been hindered by sharp extinction of the signal in high humidity conditions, e.g., clouds. To remedy this, we developed an effective and simple limiter [...] Read more.
Micro pulse lidar is a promising tool for retrieving the convective boundary layer height (CBLH), but its application has been hindered by sharp extinction of the signal in high humidity conditions, e.g., clouds. To remedy this, we developed an effective and simple limiter to obtain more accurate estimates of the CBLH. The limiter is based on the algorithm for the convective condensation level (CCL) and is aimed at limiting the vertical extent of the lidar backscatter profile used in lidar methods to search for the CBLH. Four lidar methods (i.e., the gradient method, the idealized backscatter method, and two forms of the wavelet covariance methods) are used to calculate the CBLH with (or without) the limiter added. Compared to the CBLH calculated by the parcel method from microwave radiometer temperature data, more accurate retrieval of the CBLH is carried out with the limiter applied in four cloudy cases. Full article
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Article
Mobile DOAS Observations of Tropospheric NO2 Using an UltraLight Trike and Flux Calculation
by Daniel-Eduard Constantin, Alexis Merlaud, Mirela Voiculescu, Carmelia Dragomir, Lucian Georgescu, Francois Hendrick, Gaia Pinardi and Michel Van Roozendael
Atmosphere 2017, 8(4), 78; https://doi.org/10.3390/atmos8040078 - 22 Apr 2017
Cited by 7 | Viewed by 5695
Abstract
In this study, we report on airborne Differential Optical Absorption Spectroscopy (DOAS) observations of tropospheric NO2 using an Ultralight Trike (ULT) and associated flux calculations. The instrument onboard the ULT was developed for measuring the tropospheric NO2 Vertical Column Density (VCD) [...] Read more.
In this study, we report on airborne Differential Optical Absorption Spectroscopy (DOAS) observations of tropospheric NO2 using an Ultralight Trike (ULT) and associated flux calculations. The instrument onboard the ULT was developed for measuring the tropospheric NO2 Vertical Column Density (VCD) and it was operated for several days between 2011 and 2014, in the South-East of Romania. Collocated measurements were performed using a car-DOAS instrument. Most of the airborne and mobile ground-based measurements were performed close to an industrial platform located nearby Galati city (45.43° N, 28.03° E). We found a correlation of R = 0.71 between tropospheric NO2 VCDs deduced from airborne DOAS observations and mobile ground-based DOAS observations. We also present a comparison between stratospheric NO2 Slant Column Density (SCD) derived from the Dutch OMI NO2 (DOMINO) satellite data product and stratospheric SCDs obtained from ground and airborne measurements. The airborne DOAS observations performed on 13 August 2014 were used to quantify the NO2 flux originating from an industrial platform located nearby Galati city. Measurements during a flight above the industrial plume showed a maximum tropospheric NO2 VCD of (1.41 ± 0.27) × 1016 molecules/cm2 and an associated NO2 flux of (3.45 ± 0.89) × 10−3 kg/s. Full article
(This article belongs to the Special Issue Air Quality Monitoring and Forecasting)
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Article
Using Satellite and Lightning Data to Track Rapidly Developing Thunderstorms in Data Sparse Regions
by Morné Gijben and Estelle De Coning
Atmosphere 2017, 8(4), 67; https://doi.org/10.3390/atmos8040067 - 20 Apr 2017
Cited by 18 | Viewed by 6198
Abstract
Radar systems provide the most useful information about the intensity, movement, and characteristics of severe thunderstorms, but are expensive to maintain and require extensive maintenance. In South Africa, some areas are not covered by radar systems, while very few operational radar systems exist [...] Read more.
Radar systems provide the most useful information about the intensity, movement, and characteristics of severe thunderstorms, but are expensive to maintain and require extensive maintenance. In South Africa, some areas are not covered by radar systems, while very few operational radar systems exist in other southern African countries. Despite these shortcomings, all meteorological centers still have to warn the public of pending severe weather events. The Nowcasting Satellite Application Facility (NWC SAF) in Europe developed software that utilizes satellite data to identify and track rapidly developing thunderstorms (RDT). The NWC software was installed at the South African Weather Service in 2014. Initially, the RDT product was validated against lightning data and the results showed that the RDT product could provide very useful information on possible severe or intense convective storms. This study focusses on the effects of including lightning as an ancillary dataset into the algorithms and then validating the RDT product against radar data. Twenty-five summer cases were considered to determine whether the inclusion of lightning data had a positive effect on the accuracy of the RDT product, when compared to radar data. The results of this study show that in the majority of the cases, the inclusion of lightning data was beneficial to the RDT product. On average the Probability of Detection (POD) improved by 6.6%, the Heidke Skill Score (HSS) by 4.6%, and the False alarm ratio (FAR) by 0.1%. To our knowledge, South Africa is the only African country which is running the NWC SAF software operationally and which has performed an evaluation of the product over Africa against observations from radar systems and lightning sensors. The outcomes of this study are very encouraging for other countries in Africa where convection and severe convection often occur and sophisticated data sources are absent. Initial studies over East Africa indicate that the RDT product can benefit operational practices for the nowcasting of severe convection events. Full article
(This article belongs to the Special Issue Radar Meteorology)
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9052 KiB  
Communication
A New Type of Haze? The December 2015 Purple (Magenta) Haze Event in Nanjing, China
by Duanyang Liu, Xuejun Liu, Hongbin Wang, Yi Li, Zhiming Kang, Lu Cao, Xingna Yu and Hao Chen
Atmosphere 2017, 8(4), 76; https://doi.org/10.3390/atmos8040076 - 14 Apr 2017
Cited by 5 | Viewed by 6276
Abstract
A special and unusual purple (magenta) haze episode was observed in Nanjing, China, at 17:00 on 22 December 2015. Many local and national news outlets reported this event. Based on an analysis of the pollution features and meteorological factors, including boundary layer characteristics, [...] Read more.
A special and unusual purple (magenta) haze episode was observed in Nanjing, China, at 17:00 on 22 December 2015. Many local and national news outlets reported this event. Based on an analysis of the pollution features and meteorological factors, including boundary layer characteristics, we concluded that this haze event was similar in most respects to other local haze episodes. We discuss the reasons and the possibilities about this rare color haze at the end of the paper. One way to attain a combination of blue and red light is to have the green wavelengths selectively absorbed, and this seems unlikely for typical atmospheric constituents. Another way involves pollution gases or particles together with small liquid-water drops, which need further confirmation. A third possibility is that the combination of transmitted red light from the sun and scattered blue light from above could produce a purple/magenta color in the sky. In general, further studies are required to assess the physical, chemical, and optical features of this purple haze in order to explain and predict this phenomenon in the future. Full article
(This article belongs to the Special Issue Urban Air Pollution)
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Article
PM2.5 Characteristics in Qingdao and across Coastal Cities in China
by Ruidong Wu, Xuehua Zhou, Linpeng Wang, Zhe Wang, Yang Zhou, Jingzhu Zhang and Wenxing Wang
Atmosphere 2017, 8(4), 77; https://doi.org/10.3390/atmos8040077 - 13 Apr 2017
Cited by 32 | Viewed by 6585
Abstract
A year-long study was performed to comprehensively investigate the mass concentration, water-soluble ions, organic and elemental carbons, and elemental components of atmospheric fine particles from March 2006 to February 2007 in Qingdao. The results showed that PM2.5 concentration was over twice the [...] Read more.
A year-long study was performed to comprehensively investigate the mass concentration, water-soluble ions, organic and elemental carbons, and elemental components of atmospheric fine particles from March 2006 to February 2007 in Qingdao. The results showed that PM2.5 concentration was over twice the National Ambient Air Quality Standards of 35 μg/m3 (GB3095-2012), with the highest value in winter (110 μg/m3) and the lowest in summer (42.8 μg/m3). Non-sea salt-SO42− (nss-SO42−), NO3−, and NH4+ were the dominant water-soluble ions in PM2.5, and showed the highest concentrations in autumn, winter and autumn, respectively, and all had the lowest concentrations in summer. Organic carbon (OC) and elemental carbon (EC) had the lowest levels in summer and the highest values in winter and autumn, respectively. The lower acetic/formic acid (A/F) ratio in summer suggested a predominant secondary formation of water-soluble organic acids. Cl-depletion mainly occurred in summer, along with the largest sea salt proportion in particles in a year when winds came from the southeastern sea. The enrichment factors (EFs) of elements followed an increasing order: Si, Al, Ti, Mg, Ca, Fe, Na, Sr, K, Mn, Ba, V, Cr, Ni, Co, Sc, Cu, As, Cl, Zn, Pb, S, Br, Cd, and Se. The higher EFs from 10.1 to 10,487 for Sr, K, Mn, Ba, V, Cr, Ni, Co, Sc, Cu, Cl, Zn, Pb, S, Br, Cd, and Se suggested the significant influence of anthropogenic sources in the area. Mass closure showed that (NH4)2SO4, organic matter, and NH4NO3 were the main components, and contributed 31.0%, 25.2%, and 14.0% of PM2.5 mass in Qingdao, respectively. Source apportionment results showed that secondary sulfate, nitrate, and coal combustion were the main sources. Based on this study and previous publications, the PM2.5 characteristics—including seasonality in mass and chemical species concentrations and Cl-depletion in summer—were obtained across coastal cities in China. Full article
(This article belongs to the Section Air Quality)
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Article
Analysis of the Joint Link between Extreme Temperatures, Precipitation and Climate Indices in Winter in the Three Hydroclimate Regions of Southern Quebec
by Ali A. Assani and Nadjet Guerfi
Atmosphere 2017, 8(4), 75; https://doi.org/10.3390/atmos8040075 - 12 Apr 2017
Cited by 10 | Viewed by 4919
Abstract
We analyze the relationship between four climate variables (maximum and minimum extreme temperatures, rainfall and snowfall) measured in winter (December to March) at 17 stations from 1950 to 2000 in the three hydroclimate regions of southern Quebec, and six seasonal climate indices using [...] Read more.
We analyze the relationship between four climate variables (maximum and minimum extreme temperatures, rainfall and snowfall) measured in winter (December to March) at 17 stations from 1950 to 2000 in the three hydroclimate regions of southern Quebec, and six seasonal climate indices using canonical correlation analysis (CCA) and the copula method. This analysis yielded these major results: (1) extreme temperatures are not correlated with the amount of winter rain or snow in southern Quebec; (2) winter seasonal climate indices show better correlations with climate variables than do fall climate indices; (3) winter extreme temperatures are best correlated (positive correlation) with the Atlantic Multidecadal Oscillation (AMO) in the eastern region, but show a negative correlation with the Arctic Oscillation (AO) in the southwestern region; (4) the total amount of winter snow is best correlated (negative correlation) with the Pacific Decadal Oscillation (PDO) in the three hydroclimate regions; (5) the total amount of winter rain is best (negatively) correlated with PDO in the eastern region, but shows a positive correlation with AO in the southeast region. Finally, the copula method revealed very little change in the dependence between climate indices and climate variables in the three hydroclimate regions. Full article
(This article belongs to the Special Issue Temperature Extremes and Heat/Cold Waves)
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Article
An Objective Prototype-Based Method for Dual-Polarization Radar Clutter Identification
by Guang Wen, Alain Protat and Hui Xiao
Atmosphere 2017, 8(4), 72; https://doi.org/10.3390/atmos8040072 - 10 Apr 2017
Cited by 6 | Viewed by 4981
Abstract
A prototype-based method is developed to discriminate different types of clutter (ground clutter, sea clutter, and insects) from weather echoes using polarimetric measurements and their textures. This method employs a clustering algorithm to generate data groups from the training dataset, each of which [...] Read more.
A prototype-based method is developed to discriminate different types of clutter (ground clutter, sea clutter, and insects) from weather echoes using polarimetric measurements and their textures. This method employs a clustering algorithm to generate data groups from the training dataset, each of which is modeled as a weighted Gaussian distribution called a “prototype.” Two classification algorithms are proposed based on the prototypes, namely maximum prototype likelihood classifier (MPLC) and Bayesian classifier (BC). In the MPLC, the probability of a data point with respect to each prototype is estimated to retrieve the final class label under the maximum likelihood criterion. The BC models the probability density function as a Gaussian mixture composed by the prototypes. The class label is obtained under the maximum a posterior criterion. The two algorithms are applied to S-band dual-polarization CP-2 weather radar data in Southeast Queensland, Australia. The classification results for the test dataset are compared with the NCAR fuzzy-logic particle identification algorithm. Generally good agreement is found for weather echo and ground clutter; however, the confusion matrix indicates that the techniques tend to differ from each other on the recognition of insects. Full article
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1092 KiB  
Article
Characteristics and Source Analysis of Water-Soluble Inorganic Ions in PM10 in a Typical Mining City, Central China
by Hongxia Liu, Jingru Zheng, Chengkai Qu, Jiaquan Zhang, Yongkui Wang, Changlin Zhan, Ruizhen Yao and Junji Cao
Atmosphere 2017, 8(4), 74; https://doi.org/10.3390/atmos8040074 - 8 Apr 2017
Cited by 25 | Viewed by 4757
Abstract
A total of 61 PM10 samples in Huangshi (HS), Central China, were collected every sixth day from April 2012 to March 2013 and were analyzed for water-soluble inorganic ions (WSIIs) by ion chromatography. The sum of three major ions (SO42− [...] Read more.
A total of 61 PM10 samples in Huangshi (HS), Central China, were collected every sixth day from April 2012 to March 2013 and were analyzed for water-soluble inorganic ions (WSIIs) by ion chromatography. The sum of three major ions (SO42−, NO3−, and NH4+) accounted for 75.8% of the total WSIIs on average. The results of a non-parametric test (Kruskal-Wallis) show that, except for Na+ (p > 0.05), the other ions present a distinctly seasonal variation with a statistically significant difference (p < 0.05). The minimum concentrations of all ions were found in summer, while the maximum values presented in autumn (for Ca2+) and winter (for Cl−, NO3−, SO42−, K+, NH4+, Mg2+). Based on the highest ratio of Cl−/Na+ (3.02) and the highest concentration of K (4.37 μg·m−3), Ba (0.37 μg·m−3), and Sr (0.07 μg·m−3) in February 2013, it can be concluded that firework powders have aggravated the haze weather during the Spring Festival of 2013. The micro-equivalent concentrations of cations and anions were calculated and the comparisons between the calculated and measured NH4+ concentrations were conducted. The results illustrate that aerosol particles in HS are acidic and there may exist some other cationic ions not detected in this study. An obvious positive correlation and good linear regression among WSIIs suggest that the chemical forms in HS aerosols show a great variety of combinations, such as NH4NO3, NH4HSO4, (NH4)2SO4, NH4Cl, KCl, KNO3, NaCl, NaNO3, Ca(NO3)2, CaSO4, MgCl2, Mg(NO3)2, and MgSO4. The WSIIs have large positive correlation and linear regression with the elements, suggesting that WSIIs in mining cities are strongly influenced by element constituents. Principal component analysis implies that WSIIs in PM10 are probably from three sources. NH4+, Mg2+, NO3−, K and K+, Cl− and Cl, SO42−, and S accounted for 46.9% of the total variances, suggesting likely anthropogenic sources, especially coal combustion, vehicular exhaust, and biomass burning. Mg accounted for 23.3% of the total variances and Ca2+ and Ca explained 18.1% of the total variances, demonstrating that another important source is mineral dust from both natural and anthropogenic sources. Full article
(This article belongs to the Section Air Quality)
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2375 KiB  
Article
Characteristics of Carbonaceous Aerosol in a Typical Industrial City—Nanjing in Yangtze River Delta, China: Size Distributions, Seasonal Variations, and Sources
by Honglei Wang, Junlin An, Bin Zhu, Lijuan Shen, Qing Duan and Yuanzhe Shi
Atmosphere 2017, 8(4), 73; https://doi.org/10.3390/atmos8040073 - 7 Apr 2017
Cited by 17 | Viewed by 5056
Abstract
In order to investigate the size distributions and seasonal variations of carbonaceous aerosols (organic carbon (OC) and elemental carbon (EC)), the carbonaceous species were collected in Nanjing, a typical industrial city located in Yangtze River Delta, China, in the summer, autumn, and winter [...] Read more.
In order to investigate the size distributions and seasonal variations of carbonaceous aerosols (organic carbon (OC) and elemental carbon (EC)), the carbonaceous species were collected in Nanjing, a typical industrial city located in Yangtze River Delta, China, in the summer, autumn, and winter of 2013 and spring of 2014, and then analyzed by using a 9-stage Anderson-type aerosol sampler and DRI Model 2001A Thermal/Optical Carbon Analyzer. OC, EC, secondary organic carbon (SOC), and primary organic carbon (POC) exhibited obvious seasonal variations, with the highest levels in winter (39.1±14.0, 5.7 ± 2.1, 23.6 ± 11.7, and 14.1 ± 5.7 μg·m−3, respectively) and the lowest levels in summer (20.6 ± 6.7, 3.3 ± 2.0, 12.2 ± 3.8 and 8.4 ± 4.1 μg·m−3, respectively), and were mainly centralized in PM1.1 in four seasons. The concentrations of OC in PM1.1 varied in the order of winter > autumn > spring > summer, while EC ranked in the order of autumn > winter > summer > spring. In the PM1.1–2.1 and PM2.1–10, the concentrations of OC and EC decreased in the sequence of winter > spring > autumn > summer. The size spectra of OC, EC, and SOC had bimodal distributions in four seasons, except for EC with four peaks in summer. The size spectra of POC varied greatly with seasons, exhibiting bimodal distribution in winter, trimodal distribution in spring and summer, and four peaks in autumn. The OC/EC ratios were 7.0, 6.3, 7.6, and 6.9 in spring, summer, autumn and winter, respectively, which demonstrated the abundance of secondary organic aerosols in Nanjing. The sources of carbonaceous aerosol varied significantly with seasons, and were dominated by vehicle exhaust, and coal and biomass burning in PM2.1, and dominated by dust, and coal and biomass burning in PM2.1–10. Full article
(This article belongs to the Special Issue Carbonaceous Aerosols in Atmosphere)
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4084 KiB  
Article
The Effect of Meteorological Elements on Continuing Heavy Air Pollution: A Case Study in the Chengdu Area during the 2014 Spring Festival
by Shenglan Zeng and Yu Zhang
Atmosphere 2017, 8(4), 71; https://doi.org/10.3390/atmos8040071 - 6 Apr 2017
Cited by 45 | Viewed by 7975
Abstract
Meteorological conditions significantly influence air pollution. The Chengdu plain, with few external pollution sources and homogeneous meteorological conditions, is a natural lab to study the effects of meteorological elements on the diffusion and dissipation of pollutants. Large-scale and long-duration haze events occurred all [...] Read more.
Meteorological conditions significantly influence air pollution. The Chengdu plain, with few external pollution sources and homogeneous meteorological conditions, is a natural lab to study the effects of meteorological elements on the diffusion and dissipation of pollutants. Large-scale and long-duration haze events occurred all over China during the Spring Festival in 2014. This study tries to detect the characteristics and the formation mechanisms of this haze event in the Chengdu area using air quality and the meteorological monitoring of this event. The results showed that, when considering the concentration changes of the primary pollutant, this haze event could be divided into three stages: Stage 1, the concentration of all pollutions increased; Stage 2, the concentration of gaseous pollutants decreased, while that of particulate matter increased; Stage 3, the concentration of all pollutants decreased. Adverse atmospheric circulation, unfavorable meteorological conditions (lower air temperature and wind speed, higher air pressure and relative humidity), a frequently occurring inversion layer (with a strong intensity and lower bottom), and the low height of the mixing layer resulted in this haze. This study suggests that not only surface meteorological factors, but also the boundary layer structure, played an important role in the vertical diffusion of the pollutants. Full article
(This article belongs to the Section Air Quality)
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Article
Effect of Missing Data on Estimation of the Impact of Heat Waves: Methodological Concerns for Public Health Practice
by Emily Leary, Linda J. Young, Melissa M. Jordan and Chris DuClos
Atmosphere 2017, 8(4), 70; https://doi.org/10.3390/atmos8040070 - 4 Apr 2017
Viewed by 4343
Abstract
(1) Background: To demonstrate the potential effects of missing exposure data and model choice on public health conclusions concerning the impact of heat waves on heat-related morbidity. (2) Methods: Using four different methods to impute missing exposure data, four statistical models (case-crossover, time-series, [...] Read more.
(1) Background: To demonstrate the potential effects of missing exposure data and model choice on public health conclusions concerning the impact of heat waves on heat-related morbidity. (2) Methods: Using four different methods to impute missing exposure data, four statistical models (case-crossover, time-series, zero-inflated, and truncated models) are compared. The methods are used to relate heat waves, based on heat index, and heat-related morbidities for Florida from 2005–2012. (3) Results: Truncated models using maximum daily heat index, imputed using spatio-temporal methods, provided the best model fit of regional and statewide heat-related morbidity, outperforming the commonly used case-crossover and time-series analysis methods. (4) Conclusions: The extent of missing exposure data, the method used to impute missing exposure data and the statistical model chosen can influence statistical inference. Further, using a statewide truncated negative binomial model, statistically significant associations between heat-related morbidity and regional heat index effects were identified. Full article
(This article belongs to the Special Issue Temperature Extremes and Heat/Cold Waves)
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Article
Q-Space Analysis of the Light Scattering Phase Function of Particles with Any Shape
by Christopher M. Sorensen, Yuli W. Heinson, William R. Heinson, Justin B. Maughan and Amit Chakrabarti
Atmosphere 2017, 8(4), 68; https://doi.org/10.3390/atmos8040068 - 29 Mar 2017
Cited by 20 | Viewed by 6975
Abstract
Q-space analysis is applied to the light scattering phase function of a wide variety of non-spherical and irregularly shaped particles including a great many types of dusts, fractal aggregates, spheroids, irregular spheres, Gaussian random spheres, thickened clusters and nine types of ice crystals. [...] Read more.
Q-space analysis is applied to the light scattering phase function of a wide variety of non-spherical and irregularly shaped particles including a great many types of dusts, fractal aggregates, spheroids, irregular spheres, Gaussian random spheres, thickened clusters and nine types of ice crystals. The phase functions were either experimental data or calculations. This analysis method uncovers many specific and quantitative similarities and differences between the scattering by various shapes and also when compared to spheres. From this analysis a general description for scattering by a particle of any shape emerges with specific details assigned to various shapes. Full article
(This article belongs to the Special Issue Morphology and Internal Mixing of Atmospheric Particles)
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Article
Quantifying Light Absorption of Iron Oxides and Carbonaceous Aerosol in Seasonal Snow across Northern China
by Yue Zhou, Xin Wang, Xueqin Wu, Zhiyuan Cong, Guangming Wu and Mingxia Ji
Atmosphere 2017, 8(4), 63; https://doi.org/10.3390/atmos8040063 - 28 Mar 2017
Cited by 15 | Viewed by 5239
Abstract
In this study, we attempted to quantify light absorption by insoluble light-absorbing particles (ILAPs) such as black carbon (BC), organic carbon (OC) and iron oxides in snow using an optical method directly and compared the results with those obtained using optical and chemical [...] Read more.
In this study, we attempted to quantify light absorption by insoluble light-absorbing particles (ILAPs) such as black carbon (BC), organic carbon (OC) and iron oxides in snow using an optical method directly and compared the results with those obtained using optical and chemical analysis methods cooperatively in previous studies. The mass absorption coefficients (MACs) and absorption Ångström exponents (AAEs) of pure hematite, goethite and fullerene soot were also measured using an integrating sphere/integrating sandwich (ISSW) spectrophotometer in the laboratory. The results indicated that the MACs of pure hematite and goethite are 0.97 ± 0.02 m2·g−1 and 0.43 ± 0.01 m2·g−1 at 550 nm, and their AAEs are 5.53 ± 0.47 and 2.18 ± 0.16 from 550 nm to 750 nm, respectively. The MAC and AAE of fullerene soot are 6.40 ± 0.42 m2·g−1 at 550 nm and 0.54 ± 0.06 from 450 to 750 nm. By using the regionally average AAEs of non-BC components in snow, we evaluated the performance of a directly optical analysis, rather than combination of the optical and chemical methods, in quantifying the light absorption of BC, OC and Fe in snow samples. We found that the directly optical method used to measure the light absorption of BC and OC in Northern China snow has substantially low biases of 6.29% and 4.27% in median comparing to previous method. However, the high biases in estimating light absorption of Fe (33.01%) may be associated with the significant underestimation of the AAE of Fe. Full article
(This article belongs to the Special Issue Dust Storms and Associated Impacts to Human Health and the Environment)
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Article
Characterization of Atmospheric Iron Speciation and Acid Processing at Metropolitan Newark on the US East Coast
by Guojie Xu and Yuan Gao
Atmosphere 2017, 8(4), 66; https://doi.org/10.3390/atmos8040066 - 24 Mar 2017
Cited by 6 | Viewed by 4563
Abstract
To characterize atmospheric dissolved iron over Newark, a large metropolitan city on US east coast, size-segregated (0.056–18 μm in aerodynamic diameter) aerosols were collected in downtown Newark, New Jersey during August to October 2012. Aerosols samples were analyzed for Fe(II) and total dissolved [...] Read more.
To characterize atmospheric dissolved iron over Newark, a large metropolitan city on US east coast, size-segregated (0.056–18 μm in aerodynamic diameter) aerosols were collected in downtown Newark, New Jersey during August to October 2012. Aerosols samples were analyzed for Fe(II) and total dissolved iron (Fe(TD)) by UV/Visible spectroscopy, and water soluble compounds were analyzed by ion chromatograph (IC). Results from this study showed that Fe(II) concentrations were 2.1 ng m−3 (range: 1.2–4.2 ng m−3), Fe(TD) concentrations were 2.4 ng m−3 (range: 1.3–4.9 ng m−3). Dissolved iron (Fe(II) and Fe(TD)) in general appeared as bi-modal size distribution, was mainly accumulated in the fine mode. The highest concentration of dissolved iron displayed in the fine mode, which was associated with high concentrations of sulfate, oxalate and nitrate, suggesting the potential for Fe–acids interactions. Dissolved iron presented positive correlations with sulfate in the coarse mode, and with nitrate in the fine mode, further suggesting the importance of acid processing in aerosol iron solubility. However, as the oxalate concentration was so low, a good correlation between dissolved iron and oxalate in both the fine and coarse mode was not found. Full article
(This article belongs to the Section Air Quality)
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Article
Spatial Variability and Factors Influencing the Air-Sea N2O Flux in the Bering Sea, Chukchi Sea and Chukchi Abyssal Plain
by Man Wu, Liqi Chen, Liyang Zhan, Jiexia Zhang, Yuhong Li and Jian Liu
Atmosphere 2017, 8(4), 65; https://doi.org/10.3390/atmos8040065 - 24 Mar 2017
Cited by 8 | Viewed by 4665
Abstract
The concentrations of the ozone-depleting greenhouse gas nitrous oxide (N2O) in the upper 300 m of the Subarctic and Arctic Oceans determined during the 5th Chinese National Arctic Research Expedition were studied. The surface water samples revealed that the study area [...] Read more.
The concentrations of the ozone-depleting greenhouse gas nitrous oxide (N2O) in the upper 300 m of the Subarctic and Arctic Oceans determined during the 5th Chinese National Arctic Research Expedition were studied. The surface water samples revealed that the study area could be divided into three regions according to the distribution of dissolved N2O in the surface water, namely, the Aleutian Basin (52° N–60° N), continental shelf (60° N–73° N) and Canadian Basin (north of 73° N), with N2O in the surface water in equilibrium, oversaturated and undersaturated relative to the atmosphere, respectively. The influences of physical and chemical processes, such as eddy diffusion and sedimentary emissions, beneath the surface layer are discussed. The results of a flux evaluation show that the Aleutian Basin may be a weak N2O source of approximately 0.46 ± 0.1 μmol·m−2·d−1, and the continental shelf acts as a strong N2O source of approximately 8.2 ± 1.4 μmol·m−2·d−1. By contrast, the Chukchi Abyssal Plain (CAP) of the Canadian Basin is at least a temporal N2O sink with a strength of approximately −10.2 ± 1.4 μmol·m−2·d−1. Full article
(This article belongs to the Special Issue Air-Sea Coupling)
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Article
Global Climate Responses to Land Use and Land Cover Changes Over the Past Two Millennia
by Mi Yan, Jian Liu and Zhiyuan Wang
Atmosphere 2017, 8(4), 64; https://doi.org/10.3390/atmos8040064 - 23 Mar 2017
Cited by 12 | Viewed by 5698
Abstract
A reconstructed land use/land cover change (LUCC) dataset was used with the Community Earth System Model (CESM) to conduct a climate sensitivity analysis over the past two millennia. Compared to a controlled experiment conducted with the CESM, the LUCC showed significant biogeophysical effects [...] Read more.
A reconstructed land use/land cover change (LUCC) dataset was used with the Community Earth System Model (CESM) to conduct a climate sensitivity analysis over the past two millennia. Compared to a controlled experiment conducted with the CESM, the LUCC showed significant biogeophysical effects on global climate on multi-decadal to centennial time scales. The global annual mean temperature and precipitation show clear decadal and multi-centennial scale oscillations when the LUCC effect was considered in the CESM simulation. With increased crop acreage and decreased natural vegetation over the past two millennia, the reflected terrestrial solar radiation has increased and the net terrestrial radiation has decreased, leading to a decrease in the global annual mean temperature. Global annual mean precipitation has also decreased along with decreased evaporation and atmospheric humidity. Our simulation suggests that LUCC mainly influences convective precipitation and has little influence on large-scale precipitation. The impact of LUCC has latitudinal and seasonal differences. The largest response of temperature to LUCC has occurred in the middle latitudes of the Northern Hemisphere (NH), while the largest precipitation response occurred at lower latitudes of the NH. The responses of temperature and precipitation to LUCC is stronger in winter and spring than in summer and autumn. Full article
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