Journal articles on the topic 'Aerosols Asia, Southeastern'
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1
Wang, M., B. Xu, J. Cao, X. Tie, H. Wang, R. Zhang, Y. Qian, et al. "Carbonaceous aerosols recorded in a Southeastern Tibetan glacier: variations, sources and radiative forcing." Atmospheric Chemistry and Physics Discussions 14, no. 13 (July 31, 2014): 19719–46. http://dx.doi.org/10.5194/acpd-14-19719-2014.
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Abstract. High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956–2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of OC / BC ratio with higher values in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source-receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia is a primary contributor during the non-monsoon season (October to May) (81%) and on an annual basis (74%), followed by East Asia (14% and 21%, respectively). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia as the primary contributor. Moreover, the increasing trend of OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice core record.
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Zheng, Jing, Min Hu, Zhuofei Du, Dongjie Shang, Zhaoheng Gong, Yanhong Qin, Jingyao Fang, et al. "Influence of biomass burning from South Asia at a high-altitude mountain receptor site in China." Atmospheric Chemistry and Physics 17, no. 11 (June 12, 2017): 6853–64. http://dx.doi.org/10.5194/acp-17-6853-2017.
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Abstract. Highly time-resolved in situ measurements of airborne particles were conducted at Mt. Yulong (3410 m above sea level) on the southeastern edge of the Tibetan Plateau in China from 22 March to 14 April 2015. The detailed chemical composition was measured by a high-resolution time-of-flight aerosol mass spectrometer together with other online instruments. The average mass concentration of the submicron particles (PM1) was 5.7 ± 5.4 µg m−3 during the field campaign, ranging from 0.1 up to 33.3 µg m−3. Organic aerosol (OA) was the dominant component in PM1, with a fraction of 68 %. Three OA factors, i.e., biomass burning organic aerosol (BBOA), biomass-burning-influenced oxygenated organic aerosol (OOA-BB) and oxygenated organic aerosol (OOA), were resolved using positive matrix factorization analysis. The two oxygenated OA factors accounted for 87 % of the total OA mass. Three biomass burning events were identified by examining the enhancement of black carbon concentrations and the f60 (the ratio of the signal at m∕z 60 from the mass spectrum to the total signal of OA). Back trajectories of air masses and satellite fire map data were integrated to identify the biomass burning locations and pollutant transport. The western air masses from South Asia with active biomass burning activities transported large amounts of air pollutants, resulting in elevated organic concentrations up to 4-fold higher than those of the background conditions. This study at Mt. Yulong characterizes the tropospheric background aerosols of the Tibetan Plateau during pre-monsoon season and provides clear evidence that the southeastern edge of the Tibetan Plateau was affected by the transport of anthropogenic aerosols from South Asia.
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Hatzianastassiou, Kalaitzi, Gavrouzou, Gkikas, Korras-Carraca, and Mihalopoulos. "A Climatological Satellite Assessment of Absorbing Carbonaceous Aerosols on a Global Scale." Atmosphere 10, no. 11 (November 1, 2019): 671. http://dx.doi.org/10.3390/atmos10110671.
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A global climatology of absorbing carbonaceous aerosols (ACA) for the period 2005–2015 is obtained by using satellite MODIS (Moderate Resolution Imaging Spectroradiometer)-Aqua and OMI (Ozone Monitoring Instrument)-Aura aerosol optical properties and by applying an algorithm. The algorithm determines the frequency of presence of ACA (black and brown carbon) over the globe at 1° × 1° pixel level and on a daily basis. The results of the algorithm indicate high frequencies of ACA (up to 19 days/month) over world regions with extended biomass burning, such as the tropical forests of southern and central Africa, South America and equatorial Asia, over savannas, cropland areas or boreal forests, as well as over urban and rural areas with intense anthropogenic activities, such as the eastern coast of China or the Indo-Gangetic plain. A clear seasonality of the frequency of occurrence of ACA is evident, with increased values during June–October over southern Africa, during July–November over South America, August–November over Indonesia, November–March over central Africa and November–April over southeastern Asia. The estimated seasonality of ACA is in line with the known annual patterns of worldwide biomass-burning emissions, while other features such as the export of carbonaceous aerosols from southern Africa to the southeastern Atlantic Ocean are also successfully reproduced by the algorithm. The results indicate a noticeable interannual variability and tendencies of ACA over specific world regions during 2005–2015, such as statistically significant increasing frequency of occurrence over southern Africa and eastern Asia.
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Wang, M., B. Xu, J. Cao, X. Tie, H. Wang, R. Zhang, Y. Qian, et al. "Carbonaceous aerosols recorded in a southeastern Tibetan glacier: analysis of temporal variations and model estimates of sources and radiative forcing." Atmospheric Chemistry and Physics 15, no. 3 (February 2, 2015): 1191–204. http://dx.doi.org/10.5194/acp-15-1191-2015.
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Abstract. High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956–2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of BC and OC with higher respective concentrations but a lower OC / BC ratio in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source–receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia has the largest contribution to the present-day (1996–2005) mean BC deposition at the ice-core drilling site during the non-monsoon season (October to May) (81%) and all year round (74%), followed by East Asia (14% to the non-monsoon mean and 21% to the annual mean). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from the late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia (as the primary contributor to annual mean BC deposition). Moreover, the increasing trend of the OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and/or biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing potential influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice-core record.
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Wang, Xiaodong, Chun Zhao, Mingyue Xu, Qiuyan Du, Jianqiu Zheng, Yun Bi, Shengfu Lin, and Yali Luo. "The sensitivity of simulated aerosol climatic impact to domain size using regional model (WRF-Chem v3.6)." Geoscientific Model Development 15, no. 1 (January 12, 2022): 199–218. http://dx.doi.org/10.5194/gmd-15-199-2022.
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Abstract. Domain size can have significant impact on regional modeling results, but few studies examined the sensitivities of simulated aerosol impact to regional domain size. This study investigates the regional modeling sensitivities of aerosol impact on the East Asian summer monsoon (EASM) to domain size. The simulations with two different domain sizes demonstrate consistently that aerosols induce the cooling of the lower troposphere that leads to the anticyclone circulation anomalies and thus the weakening of EASM moisture transport. The aerosol-induced adjustment of monsoonal circulation results in an alternate increase and decrease pattern of precipitation over China. Domain size has a great influence on the simulated meteorological fields. For example, the simulation with larger domain size produces weaker EASM circulation, which also affects aerosol distributions significantly. This leads to the difference of simulated strength and area extent of aerosol-induced changes of lower-tropospheric temperature and pressure, which further results in different distributions of circulation and precipitation anomalies over China. For example, over southeastern China, aerosols induce the increase (decrease) of precipitation from the smaller-domain (larger-domain) simulation. Different domain sizes consistently simulate an aerosol-induced increase in precipitation around 30∘ N over eastern China. This study highlights the important influence of domain size on regional modeling results of aerosol impact on circulation and precipitation, which may not be limited to East Asia. More generally, this study also implies that proper modeling of meteorological fields with appropriate domain size is one of the keys to simulating robust aerosol climatic impact.
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Zanis, Prodromos, Dimitris Akritidis, Aristeidis K. Georgoulias, Robert J. Allen, Susanne E. Bauer, Olivier Boucher, Jason Cole, et al. "Fast responses on pre-industrial climate from present-day aerosols in a CMIP6 multi-model study." Atmospheric Chemistry and Physics 20, no. 14 (July 17, 2020): 8381–404. http://dx.doi.org/10.5194/acp-20-8381-2020.
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Abstract. In this work, we use Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations from 10 Earth system models (ESMs) and general circulation models (GCMs) to study the fast climate responses on pre-industrial climate, due to present-day aerosols. All models carried out two sets of simulations: a control experiment with all forcings set to the year 1850 and a perturbation experiment with all forcings identical to the control, except for aerosols with precursor emissions set to the year 2014. In response to the pattern of all aerosols effective radiative forcing (ERF), the fast temperature responses are characterized by cooling over the continental areas, especially in the Northern Hemisphere, with the largest cooling over East Asia and India, sulfate being the dominant aerosol surface temperature driver for present-day emissions. In the Arctic there is a warming signal for winter in the ensemble mean of fast temperature responses, but the model-to-model variability is large, and it is presumably linked to aerosol-induced circulation changes. The largest fast precipitation responses are seen in the tropical belt regions, generally characterized by a reduction over continental regions and presumably a southward shift of the tropical rain belt. This is a characteristic and robust feature among most models in this study, associated with weakening of the monsoon systems around the globe (Asia, Africa and America) in response to hemispherically asymmetric cooling from a Northern Hemisphere aerosol perturbation, forcing possibly the Intertropical Convergence Zone (ITCZ) and tropical precipitation to shift away from the cooled hemisphere despite that aerosols' effects on temperature and precipitation are only partly realized in these simulations as the sea surface temperatures are kept fixed. An interesting feature in aerosol-induced circulation changes is a characteristic dipole pattern with intensification of the Icelandic Low and an anticyclonic anomaly over southeastern Europe, inducing warm air advection towards the northern polar latitudes in winter.
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Lawrence, M. G., and J. Lelieveld. "Atmospheric pollutant outflow from southern Asia: a review." Atmospheric Chemistry and Physics Discussions 10, no. 4 (April 15, 2010): 9463–646. http://dx.doi.org/10.5194/acpd-10-9463-2010.
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Abstract. Southern Asia is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ), located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal with the trade winds, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern Asian atmospheric pollutant outflow and its large scale effects.
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Veefkind, J. P., K. F. Boersma, J. Wang, T. Kurosu, N. Krotkov, and P. F. Levelt. "Global analysis of the relation between aerosols and short-lived trace gases." Atmospheric Chemistry and Physics Discussions 10, no. 8 (August 11, 2010): 18919–51. http://dx.doi.org/10.5194/acpd-10-18919-2010.
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Abstract. The spatial and temporal correlations between concurrent satellite observations of aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and tropospheric columns of nitrogen dioxide, sulfur dioxide, and formaldehyde from the Ozone Monitoring Instrument (OMI) are used to infer information on the global composition of aerosol particles. When averaging the satellite data over large regions and longer time periods, we find significant correlation between MODIS AOT and OMI trace gas columns for various regions in the world. This suggests that enhanced aerosol and trace gas concentrations originate from common sources, such as fossil fuel combustion, biomass burning, and organic compounds released from the biosphere. This leads us to propose that satellite-inferred AOT to NO2 ratios for regions with comparable photochemical regimes can be used as indicators for the relative (local) efficiency of combustion processes. Indeed, satellites observe low AOT to NO2 ratios over the eastern United States and western Europe, and high AOT to NO2 ratios over comparably industrialized regions in eastern Europe and China. Emission databases and OMI SO2 observations over these regions suggest a much stronger sulfur contribution to aerosol formation than over the well-regulated areas of the eastern United States and western Europe. Furthermore, satellite observations show AOT to NO2 ratios are a factor 100 higher over biomass burning regions than over industrialized areas, reflecting the unregulated burning practices with strong primary particle emissions in the tropics compared to the heavily controlled combustion processes in the industrialized Northern Hemisphere. Simulations with a global chemistry transport model (GEOS-Chem) capture most of these differences, providing some confidence in our understanding of aerosol sources, formation mechanisms, and sinks. Wintertime aerosol concentrations show strongest correlations with NO2 throughout most of the Northern Hemisphere. During summertime, AOT is often (also) correlated with enhanced HCHO concentrations, reflecting the importance of secondary organic aerosol formation in that season. We also find significant correlations between AOT and HCHO over biomass burning regions, the tropics in general, and over industrialized regions in southeastern Asia. The distinct summertime maximum in AOT (0.4 at 550 nm) and HCHO over the southeastern United States strengthens existing hypotheses that local emissions of volatile organic compounds lead to the formation of secondary organic aerosols there. GEOS-Chem underestimates the AOT over the southeastern United States by a factor of 2, most likely due to too strong precipitation and too low SOA yield in the model.
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Lawrence, M. G., and J. Lelieveld. "Atmospheric pollutant outflow from southern Asia: a review." Atmospheric Chemistry and Physics 10, no. 22 (November 25, 2010): 11017–96. http://dx.doi.org/10.5194/acp-10-11017-2010.
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Abstract. Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ), located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern Asian atmospheric pollutant outflow and its large scale effects. An outlook is provided as a guideline for future research, pointing out particularly critical issues such as: resolving discrepancies between top down and bottom up emissions estimates; assessing the processing and aging of the pollutant outflow; developing a better understanding of the observed elevated pollutant layers and their relationship to local sea breeze and large scale monsoon circulations; and determining the impacts of the pollutant outflow on the Asian monsoon meteorology and the regional hydrological cycle, in particular the mountain cryospheric reservoirs and the fresh water supply, which in turn directly impact the lives of over a billion inhabitants of southern Asia.
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Niu, Hewen, Shichang Kang, Hailong Wang, Rudong Zhang, Xixi Lu, Yun Qian, Rukumesh Paudyal, Shijin Wang, Xiaofei Shi, and Xingguo Yan. "Seasonal variation and light absorption property of carbonaceous aerosol in a typical glacier region of the southeastern Tibetan Plateau." Atmospheric Chemistry and Physics 18, no. 9 (May 7, 2018): 6441–60. http://dx.doi.org/10.5194/acp-18-6441-2018.
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Abstract. Deposition and accumulation of light-absorbing carbonaceous aerosol on glacier surfaces can alter the energy balance of glaciers. In this study, 2 years (December 2014 to December 2016) of continuous observations of carbonaceous aerosols in the glacierized region of the Mt. Yulong and Ganhaizi (GHZ) basin are analyzed. The average elemental carbon (EC) and organic carbon (OC) concentrations were 1.51±0.93 and 2.57±1.32 µg m−3, respectively. Although the annual mean OC ∕ EC ratio was 2.45±1.96, monthly mean EC concentrations during the post-monsoon season were even higher than OC in the high altitudes (approximately 5000 ma.s.l.) of Mt. Yulong. Strong photochemical reactions and local tourism activities were likely the main factors inducing high OC ∕ EC ratios in the Mt. Yulong region during the monsoon season. The mean mass absorption efficiency (MAE) of EC, measured for the first time in Mt. Yulong, at 632 nm with a thermal-optical carbon analyzer using the filter-based method, was 6.82±0.73 m2 g−1, comparable with the results from other studies. Strong seasonal and spatial variations of EC MAE were largely related to the OC abundance. Source attribution analysis using a global aerosol–climate model, equipped with a black carbon (BC) source tagging technique, suggests that East Asia emissions, including local sources, have the dominant contribution (over 50 %) to annual mean near-surface BC in the Mt. Yulong area. There is also a strong seasonal variation in the regional source apportionment. South Asia has the largest contribution to near-surface BC during the pre-monsoon season, while East Asia dominates the monsoon season and post-monsoon season. Results in this study have great implications for accurately evaluating the influences of carbonaceous matter on glacial melting and water resource supply in glacierization areas.
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Veefkind, J. P., K. F. Boersma, J. Wang, T. P. Kurosu, N. Krotkov, K. Chance, and P. F. Levelt. "Global satellite analysis of the relation between aerosols and short-lived trace gases." Atmospheric Chemistry and Physics 11, no. 3 (February 14, 2011): 1255–67. http://dx.doi.org/10.5194/acp-11-1255-2011.
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Abstract. The spatial and temporal correlations between concurrent satellite observations of aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and tropospheric columns of nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) from the Ozone Monitoring Instrument (OMI) are used to infer information on the global composition of aerosol particles. When averaging the satellite data over large regions and longer time periods, we find significant correlation between MODIS AOT and OMI trace gas columns for various regions in the world. This shows that these enhanced aerosol and trace gas concentrations originate from common sources, such as fossil fuel combustion, biomass burning, and organic compounds released from the biosphere. This leads us to propose that satellite-inferred AOT to NO2 ratios for regions with comparable photochemical regimes can be used as indicators for the relative regional pollution control of combustion processes. Indeed, satellites observe low AOT to NO2 ratios over the eastern United States and western Europe, and high AOT to NO2 ratios over comparably industrialized regions in eastern Europe and China. Emission databases and OMI SO2 observations over these regions suggest a much stronger sulfur contribution to aerosol formation than over the well-regulated areas of the eastern United States and western Europe. Furthermore, satellite observations show AOT to NO2 ratios are a factor 100 higher over biomass burning regions than over industrialized areas, reflecting the unregulated burning practices with strong primary particle emissions in the tropics compared to the heavily controlled combustion processes in the industrialized Northern Hemisphere. Simulations with a global chemistry transport model (GEOS-Chem) capture most of these variations, although on regional scales significant differences are found. Wintertime aerosol concentrations show strongest correlations with NO2 throughout most of the Northern Hemisphere. During summertime, AOT is often (also) correlated with enhanced HCHO concentrations, reflecting the importance of secondary organic aerosol formation in that season. We also find significant correlations between AOT and HCHO over biomass burning regions, the tropics in general, and over industrialized regions in southeastern Asia. The distinct summertime maximum in AOT (0.4 at 550 nm) and HCHO over the southeastern United States strengthens existing hypotheses that local emissions of volatile organic compounds lead to the formation of secondary organic aerosols there. GEOS-Chem underestimates the AOT over the southeastern United States by a factor of 2, most likely due to too strong precipitation and too low SOA yield in the model.
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Lin, Chin-An, Yi-Chun Chen, Chian-Yi Liu, Wei-Ting Chen, John H. Seinfeld, and Charles C. K. Chou. "Satellite-Derived Correlation of SO2, NO2, and Aerosol Optical Depth with Meteorological Conditions over East Asia from 2005 to 2015." Remote Sensing 11, no. 15 (July 24, 2019): 1738. http://dx.doi.org/10.3390/rs11151738.
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Intense economic and industrial development in China has been accompanied by severe local air pollution, as well as in other downwind countries in East Asia. This study analyzes satellite observational data of sulfur dioxide (SO2), nitrogen dioxide (NO2), and aerosol optical depth (AOD) to explore the spatial distribution, long-term temporal variation, and correlation to meteorological conditions over this region over the period 2005–2015. SO2 and NO2 data are retrieved from the ozone monitoring instrument (OMI) onboard the National Aeronautics and Space Administration (NASA) Aura satellite, while AOD data are from the moderate-resolution imaging spectroradiometer (MODIS) onboard the NASA Aqua satellite. Spatial distributions of SO2, NO2, and AOD show the highest levels in the North China Plain (NCP), with hotspots also in Southeastern China (SC) and the Sichuan Basin (SB). Biomass burning also contributes to a high level of AOD in Southeast Asia in spring and in Equatorial Asia in fall. Considering the correlation of pollutant levels to meteorological conditions, monitoring data show that higher temperature and higher relative humidity (RH) favor the conversion of SO2 and NO2 to sulfate and nitrate aerosol, respectively. The impact of stronger lower tropospheric stability facilitates the accumulation of SO2 and NO2 in NCP and SC. Transport of SO2 and NO2 from intense source regions to relatively clean regions is highly influential over East Asia; such transport from the NCP leads to a considerable increase of pollutants in SC, SB, Taiwan Island (TW), and Taiwan Strait (TWS), particularly in winter. Aerosols generated by biomass burning in Southeast Asia and anthropogenic aerosol in SC are transported to TW and TWS and lead to the increase of AOD, with the highest levels of AOD in SC, TW, and TWS occurring in spring. Precipitation results in the removal of pollutants, especially in highly polluted regions, the effect of which is most significant in winter and spring.
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Jethva, Hiren, Omar Torres, and Changwoo Ahn. "A 12-year long global record of optical depth of absorbing aerosols above the clouds derived from the OMI/OMACA algorithm." Atmospheric Measurement Techniques 11, no. 10 (October 24, 2018): 5837–64. http://dx.doi.org/10.5194/amt-11-5837-2018.
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Abstract. Aerosol–cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of adequate knowledge of the complex microphysical and radiative processes of the aerosol–cloud system. Situations when light-absorbing aerosols such as carbonaceous particles and windblown dust overlay low-level cloud decks are commonly found in several regions of the world. Contrary to the known cooling effects of these aerosols in cloud-free scenario over darker surfaces, an overlapping situation of the absorbing aerosols over the cloud can lead to a significant level of atmospheric absorption exerting a positive radiative forcing (warming) at the top of the atmosphere. We contribute to this topic by introducing a new global product of above-cloud aerosol optical depth (ACAOD) of absorbing aerosols retrieved from the near-UV observations made by the Ozone Monitoring Instrument (OMI) onboard NASA's Aura platform. Physically based on an unambiguous “color ratio” effect in the near-UV caused by the aerosol absorption above the cloud, the OMACA (OMI above-cloud aerosols) algorithm simultaneously retrieves the optical depths of aerosols and clouds under a prescribed state of the atmosphere. The OMACA algorithm shares many similarities with the two-channel cloud-free OMAERUV algorithm, including the use of AIRS carbon monoxide for aerosol type identification, CALIOP-based aerosol layer height dataset, and an OMI-based surface albedo database. We present the algorithm architecture, inversion procedure, retrieval quality flags, initial validation results, and results from a 12-year long OMI record (2005–2016) including global climatology of the frequency of occurrence, ACAOD, and aerosol-corrected cloud optical depth. A comparative analysis of the OMACA-retrieved ACAOD, collocated with equivalent accurate measurements from the HSRL-2 lidar for the ORACLES Phase I operation (August–September 2016), revealed a good agreement (R = 0.77, RMSE = 0.10). The long-term OMACA record reveals several important regions of the world, where the carbonaceous aerosols from the seasonal biomass burning and mineral dust originated over the continents are found to overlie low-level cloud decks with moderate (0.3 < ACAOD < 0.5, away from the sources) to higher levels of ACAOD (> 0.8 in the proximity to the sources), including the southeastern Atlantic Ocean, southern Indian Ocean, Southeast Asia, the tropical Atlantic Ocean off the coast of western Africa, and northern Arabian sea. No significant long-term trend in the frequency of occurrence of aerosols above the clouds and ACAOD is noticed when OMI observations that are free from the “row anomaly” throughout the operation are considered. If not accounted for, the effects of aerosol absorption above the clouds introduce low bias in the retrieval of cloud optical depth with a profound impact on increasing ACAOD and cloud brightness. The OMACA aerosol product from OMI presented in this paper offers a crucial missing piece of information from the aerosol loading above cloud that will help us to quantify the radiative effects of clouds when overlaid with aerosols and their resultant impact on cloud properties and climate.
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Nair, Vijayakumar S., K. Krishna Moorthy, S. Suresh Babu, and S. K. Satheesh. "Optical and Physical Properties of Atmospheric Aerosols over the Bay of Bengal during ICARB." Journal of the Atmospheric Sciences 66, no. 9 (September 1, 2009): 2640–58. http://dx.doi.org/10.1175/2009jas3032.1.
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Abstract Simultaneous and collocated measurements of total and hemispherical backscattering coefficients (σ and β, respectively) at three wavelengths, mass size distributions, and columnar spectral aerosol optical depth (AOD) were made onboard an extensive cruise experiment covering, for the first time, the entire Bay of Bengal (BoB) and northern Indian Ocean. The results are synthesized to understand the optical properties of aerosols in the marine atmospheric boundary layer and their dependence on the size distribution. The observations revealed distinct spatial and spectral variations of all the aerosol parameters over the BoB and the presence of strong latitudinal gradients. The size distributions varied spatially, with the majority of accumulation modes decreasing from north to south. The scattering coefficient decreased from very high values (resembling those reported for continental/urban locations) in the northern BoB to very low values seen over near-pristine environments in the southeastern BoB. The average mass scattering efficiency of BoB aerosols was found to be 2.66 ± 0.1 m2 g−1 at 550 nm. The spectral dependence of columnar AOD deviated significantly from that of the scattering coefficients in the northern BoB, implying vertical heterogeneity in the aerosol type in that region. However, a more homogeneous scenario was observed in the southern BoB. Simultaneous lidar and in situ measurements onboard an aircraft over the ocean revealed the presence of elevated aerosol layers of enhanced extinction at altitudes of 1 to 3 km with an offshore extent of a few hundred kilometers. Back-trajectory analyses showed these layers to be associated with advection from west Asia and western India. The large spatial variations and vertical heterogeneity in aerosol properties, revealed by the present study, need to be included in the regional radiative forcing over the Bay of Bengal.
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Kim, Jong-Min, Hyo-Jung Lee, Hyun-Young Jo, Yu-Jin Jo, and Cheol-Hee Kim. "Vertical Characteristics of Secondary Aerosols Observed in the Seoul and Busan Metropolitan Areas of Korea during KORUS-AQ and Associations with Meteorological Conditions." Atmosphere 12, no. 11 (November 2, 2021): 1451. http://dx.doi.org/10.3390/atmos12111451.
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In this study, the chemical components of aerosols observed at ground level and in upper layers during the Korea–United States Air Quality (KORUS-AQ) campaign were analyzed in two representative metropolitan areas of Korea: the Seoul metropolitan area (SMA) and the Busan-containing southeastern metropolitan area (BMA). First, we characterized emissions using the Clean Air Policy Support System (CAPSS) emission statistics, and compared them with both ground- and aircraft-based measurements obtained during the KORUS-AQ campaign. The emission statistics showed that the SMA had higher NOx levels, whereas BMA had significantly higher SO2 levels. Ground-level observations averaged for the summer season also showed SMA–nitrate and BMA–sulfate relationships, reflecting the CAPSS emission characteristics of both areas. However, organic carbon (OC) was higher in BMA than SMA by a factor of 1.7, despite comparable volatile organic compound (VOC) emissions in the two areas. DC-8 aircraft-based measurements showed that, in most cases, nitrogen-rich localities were found in the SMA, reflecting the emission characteristics of precursors in the two sampling areas, whereas sulfur-rich localities in the BMA were not apparent from either ground-based or aircraft observations. KORUS-AQ measurements were classified according to two synoptic conditions, stagnant (STG) and long-range transport (LRT), and the nitrate-to-sulfate (N/S) ratio in both ground and upper layers was higher in the SMA for both cases. Meanwhile, organic aerosols reflected local emissions characteristics in only the STG case, indicating that this stagnant synoptic condition reflect local aerosol characteristics. The LRT case showed elevated peaks of all species at altitudes of 1.0–3.5 km, indicating the importance of LRT processes for predicting and diagnosing aerosol vertical distributions over Northeast Asia. Other chemical characteristics of aerosols in the two metropolitan areas were also compared.
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Fu, J. S., N. C. Hsu, Y. Gao, K. Huang, C. Li, N. H. Lin, and S. C. Tsay. "A regional chemical transport modeling to identify the influences of biomass burning during 2006 BASE-ASIA." Atmospheric Chemistry and Physics Discussions 11, no. 1 (January 28, 2011): 3071–115. http://dx.doi.org/10.5194/acpd-11-3071-2011.
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Abstract. To evaluate the impact of biomass burning from Southeast Asia to East Asia, this study conducted numerical simulations during NASA's 2006 Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment (BASE-ASIA). Two typical episode periods (27–28 March and 13–14 April) were examined. Two emission inventories, FLAMBE and GFED, were used in the simulations. The influences during two episodes in the source region (Southeast Asia) contributed to CO, O3 and PM2.5 concentrations as high as 400 ppbv, 20 ppbv and 80 μg/m3, respectively. The perturbations with and without biomass burning of the above three species were in the range of 10 to 60%, 10 to 20% and 30 to 70%, respectively. The impact due to long-range transport could spread over the southeastern parts of East Asia and could reach about 160 to 360 ppbv, 8 to 18 ppbv and 8 to 64 μg/m3 on CO, O3 and PM2.5, respectively; the percentage impact could reach 20 to 50% on CO, 10 to 30% on O3, and as high as 70% on PM2.5. An impact pattern can be found in April, while the impact becomes slightly broader and goes up to Yangtze River Delta. Two cross-sections at 15° N and 20° N were used to compare the vertical flux of biomass burning. In the source region (Southeast Asia), CO, O3 and PM2.5 concentrations had a strong upward tendency from surface to high altitudes. The eastward transport becomes strong from 2 to 8 km in the free troposphere. The subsidence contributed 60 to 70%, 20 to 50%, and 80% on CO, O3 and PM2.5, respectively to surface in the downwind area. The study reveals the significant impact of Southeastern Asia biomass burning on the air quality in both local and downwind areas, particularly during biomass burning episodes. This modeling study might provide constraints of lower limit. An additional study is underway for an active biomass burning year to obtain an upper limit and climate effects.
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Fu, J. S., N. C. Hsu, Y. Gao, K. Huang, C. Li, N. H. Lin, and S. C. Tsay. "Evaluating the influences of biomass burning during 2006 BASE-ASIA: a regional chemical transport modeling." Atmospheric Chemistry and Physics Discussions 11, no. 12 (December 7, 2011): 32205–43. http://dx.doi.org/10.5194/acpd-11-32205-2011.
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Abstract. To evaluate the impact of biomass burning from Southeast Asia to East Asia, this study conducted numerical simulations during NASA's 2006 Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment (BASE-ASIA). Two typical episode periods (27–28 March and 13–14 April) were examined. Two emission inventories, FLAMBE and GFED, were used in the simulations. The influences during two episodes in the source region (Southeast Asia) contributed to the surface CO, O3 and PM2.5 concentrations as high as 400 ppbv, 20 ppbv and 80 μg m−3, respectively. The perturbations with and without biomass burning of the above three species during the intense episodes were in the range of 10 to 60%, 10 to 20% and 30 to 70%, respectively. The impact due to long-range transport could spread over the southeastern parts of East Asia and could reach about 160 to 360 ppbv, 8 to 18 ppbv and 8 to 64 μg m−3 on CO, O3 and PM2.5, respectively; the percentage impact could reach 20 to 50% on CO, 10 to 30% on O3, and as high as 70% on PM2.5. In March, the impact of biomass burning was mainly concentrated in Southeast Asia and Southern China, while in April the impact becomes slightly broader, potentially including the Yangtze River Delta region. Two cross-sections at 15° N and 20° N were used to compare the vertical flux of biomass burning. In the source region (Southeast Asia), CO, O3 and PM2.5 concentrations had a strong upward transport from surface to high altitudes. The eastward transport becomes strong from 2 to 8 km in the free troposphere. The subsidence process during the long-range transport contributed 60 to 70%, 20 to 50%, and 80% to CO, O3 and PM2.5, respectively to surface in the downwind area. The study reveals the significant impact of Southeastern Asia biomass burning on the air quality in both local and downwind areas, particularly during biomass burning episodes. This modeling study might provide lower limit constraints. An additional study is underway for an active biomass burning year to obtain an upper limit and climate effects.
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Fu, J. S., N. C. Hsu, Y. Gao, K. Huang, C. Li, N. H. Lin, and S. C. Tsay. "Evaluating the influences of biomass burning during 2006 BASE-ASIA: a regional chemical transport modeling." Atmospheric Chemistry and Physics 12, no. 9 (May 2, 2012): 3837–55. http://dx.doi.org/10.5194/acp-12-3837-2012.
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Abstract. To evaluate the impact of biomass burning from Southeast Asia to East Asia, this study conducted numerical simulations during NASA's 2006 Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment (BASE-ASIA). Two typical episode periods (27–28 March and 13–14 April) were examined. Two emission inventories, FLAMBE and GFED, were used in the simulations. The influences during two episodes in the source region (Southeast Asia) contributed to the surface CO, O3 and PM2.5 concentrations as high as 400 ppbv, 20 ppbv and 80 μg m−3, respectively. The perturbations with and without biomass burning of the above three species during the intense episodes were in the range of 10 to 60%, 10 to 20% and 30 to 70%, respectively. The impact due to long-range transport could spread over the southeastern parts of East Asia and could reach about 160 to 360 ppbv, 8 to 18 ppbv and 8 to 64 μg m−3 on CO, O3 and PM2.5, respectively; the percentage impact could reach 20 to 50% on CO, 10 to 30% on O3, and as high as 70% on PM2.5. In March, the impact of biomass burning mainly concentrated in Southeast Asia and southern China, while in April the impact becomes slightly broader and even could go up to the Yangtze River Delta region. Two cross-sections at 15° N and 20° N were used to compare the vertical flux of biomass burning. In the source region (Southeast Asia), CO, O3 and PM2.5 concentrations had a strong upward transport from surface to high altitudes. The eastward transport becomes strong from 2 to 8 km in the free troposphere. The subsidence process during the long-range transport contributed 60 to 70%, 20 to 50%, and 80% on CO, O3 and PM2.5, respectively to surface in the downwind area. The study reveals the significant impact of Southeastern Asia biomass burning on the air quality in both local and downwind areas, particularly during biomass burning episodes. This modeling study might provide constraints of lower limit. An additional study is underway for an active biomass burning year to obtain an upper limit and climate effects.
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Alvim, Débora Souza, Júlio Barboza Chiquetto, Monica Tais Siqueira D’Amelio, Bushra Khalid, Dirceu Luis Herdies, Jayant Pendharkar, Sergio Machado Corrêa, et al. "Evaluating Carbon Monoxide and Aerosol Optical Depth Simulations from CAM-Chem Using Satellite Observations." Remote Sensing 13, no. 11 (June 7, 2021): 2231. http://dx.doi.org/10.3390/rs13112231.
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The scope of this work was to evaluate simulated carbon monoxide (CO) and aerosol optical depth (AOD) from the CAM-chem model against observed satellite data and additionally explore the empirical relationship of CO, AOD and fire radiative power (FRP). The simulated seasonal global concentrations of CO and AOD were compared, respectively, with the Measurements of Pollution in the Troposphere (MOPITT) and the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite products for the period 2010–2014. The CAM-chem simulations were performed with two configurations: (A) tropospheric-only; and (B) tropospheric with stratospheric chemistry. Our results show that the spatial and seasonal distributions of CO and AOD were reasonably reproduced in both model configurations, except over central China, central Africa and equatorial regions of the Atlantic and Western Pacific, where CO was overestimated by 10–50 ppb. In configuration B, the positive CO bias was significantly reduced due to the inclusion of dry deposition, which was not present in the model configuration A. There was greater CO loss due to the chemical reactions, and shorter lifetime of the species with stratospheric chemistry. In summary, the model has difficulty in capturing the exact location of the maxima of the seasonal AOD distributions in both configurations. The AOD was overestimated by 0.1 to 0.25 over desert regions of Africa, the Middle East and Asia in both configurations, but the positive bias was even higher in the version with added stratospheric chemistry. By contrast, the AOD was underestimated over regions associated with anthropogenic activity, such as eastern China and northern India. Concerning the correlations between CO, AOD and FRP, high CO is found during March–April–May (MAM) in the Northern Hemisphere, mainly in China. In the Southern Hemisphere, high CO, AOD, and FRP values were found during August–September–October (ASO) due to fires, mostly in South America and South Africa. In South America, high AOD levels were observed over subtropical Brazil, Paraguay and Bolivia. Sparsely urbanized regions showed higher correlations between CO and FRP (0.7–0.9), particularly in tropical areas, such as the western Amazon region. There was a high correlation between CO and aerosols from biomass burning at the transition between the forest and savanna environments over eastern and central Africa. It was also possible to observe the transport of these pollutants from the African continent to the Brazilian coast. High correlations between CO and AOD were found over southeastern Asian countries, and correlations between FRP and AOD (0.5–0.8) were found over higher latitude regions such as Canada and Siberia as well as in tropical areas. Higher correlations between CO and FRP are observed in Savanna and Tropical forests (South America, Central America, Africa, Australia, and Southeast Asia) than FRP x AOD. In contrast, boreal forests in Russia, particularly in Siberia, show a higher FRP x AOD correlation than FRP x CO. In tropical forests, CO production is likely favored over aerosol, while in temperate forests, aerosol production is more than CO compared to tropical forests. On the east coast of the United States, the eastern border of the USA with Canada, eastern China, on the border between China, Russia, and Mongolia, and the border between North India and China, there is a high correlation of CO x AOD and a low correlation between FRP with both CO and AOD. Therefore, such emissions in these regions are not generated by forest fires but by industries and vehicular emissions since these are densely populated regions.
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Boris, A. J., T. Lee, T. Park, J. Choi, S. J. Seo, and J. L. Collett Jr. "Fog composition at Baengnyeong Island in the eastern Yellow Sea: detecting markers of aqueous atmospheric oxidations." Atmospheric Chemistry and Physics 16, no. 2 (January 19, 2016): 437–53. http://dx.doi.org/10.5194/acp-16-437-2016.
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Abstract. Samples of fog water were collected at Baengnyeong Island (BYI) in the Yellow Sea during the summer of 2014. The most abundant chemical species in the fog water were NH4+ (mean of 2220 µM), NO3− (1260 µM), SO4−2 (730 µM), and Na+ (551 µM), with substantial contributions from other species consistent with marine and biomass burning influence on some dates. The pH of the samples ranged between 3.48 and 5.00, with a mean of 3.94, intermediate within pH values of fog/cloud water reported previously in Southeast Asia. Back trajectories (72 h) showed that high relative humidity ( > 80 %) was encountered upwind of the sampling site by all but one of the sampled air masses, and that the fog composition at BYI can be impacted by several different source regions, including the Sea of Japan, southeastern China, northeastern China, and the East China Sea. Sulfur in the collected fog was highly oxidized: low S(IV) concentrations were measured (mean of 2.36 µM) in contrast to SO4−2 and in contrast to fog/cloud S(IV) concentrations from pollutant source regions; organosulfate species were also observed and were most likely formed through aging of mainly biogenic volatile organic compounds. Low-molecular-mass organic acids were major contributors to total organic carbon (TOC; 36–69 %), comprising a fraction of TOC at the upper end of that seen in fogs and clouds in other polluted environments. Large contributions were observed from not only acetic and formic acids but also oxalic, succinic, maleic, and other organic acids that can be produced in aqueous atmospheric organic processing (AAOP) reactions. These samples of East Asian fog water containing highly oxidized components represent fog downwind of pollutant sources and can provide new insight into the fate of regional emissions. In particular, these samples demonstrate the result of extensive photochemical aging during multiday transport, including oxidation within wet aerosols and fogs.
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Zhang, Zhibo, Kerry Meyer, Hongbin Yu, Steven Platnick, Peter Colarco, Zhaoyan Liu, and Lazaros Oreopoulos. "Shortwave direct radiative effects of above-cloud aerosols over global oceans derived from 8 years of CALIOP and MODIS observations." Atmospheric Chemistry and Physics 16, no. 5 (March 4, 2016): 2877–900. http://dx.doi.org/10.5194/acp-16-2877-2016.
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Abstract. In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DREs) of above-cloud aerosols (ACAs) over global oceans using 8 years (2007–2014) of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: southeastern (SE) Atlantic region, where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over the African Savanna; tropical northeastern (TNE) Atlantic and the Arabian Sea, where ACAs are predominantly windblown dust from the Sahara and Arabian deserts, respectively; and the northwestern (NW) Pacific, where ACAs are mostly transported smoke and polluted dusts from Asian. From radiative transfer simulations based on CALIOP–MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in the TNE Atlantic Ocean and the Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m−2 (range of −0.03 to 0.06 W m−2) at TOA. The DREs at surface and within the atmosphere are −0.15 W m−2 (range of −0.09 to −0.21 W m−2), and 0.17 W m−2 (range of 0.11 to 0.24 W m−2), respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region, the JJA (July–August) seasonal mean cloudy-sky DRE is about 0.7 W m−2 (range of 0.2 to 1.2 W m−2) at TOA. All our DRE computations are publicly available1. The uncertainty in our DRE computations is mainly caused by the uncertainties in the aerosol optical properties, in particular aerosol absorption, the uncertainties in the CALIOP operational aerosol optical thickness retrieval, and the ignorance of cloud and potential aerosol diurnal cycle. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the uncertainty. 1 https://drive.google.com/folderview?id=0B6gKx4dgNY0GMVYzcEd0bkZmRmc&usp=sharing
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Liu, Huikun, Qiyuan Wang, Li Xing, Yong Zhang, Ting Zhang, Weikang Ran, and Junji Cao. "Measurement report: quantifying source contribution of fossil fuels and biomass-burning black carbon aerosol in the southeastern margin of the Tibetan Plateau." Atmospheric Chemistry and Physics 21, no. 2 (January 26, 2021): 973–87. http://dx.doi.org/10.5194/acp-21-973-2021.
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Abstract. Anthropogenic emissions of black carbon (BC) aerosol are transported from Southeast Asia to the southwestern Tibetan Plateau (TP) during the pre-monsoon; however, the quantities of BC from different anthropogenic sources and the transport mechanisms are still not well constrained because there have been no high-time-resolution BC source apportionments. Intensive measurements were taken in a transport channel for pollutants from Southeast Asia to the southeastern margin of the TP during the pre-monsoon to investigate the influences of fossil fuels and biomass burning on BC. A receptor model that coupled multi-wavelength absorption with aerosol species concentrations was used to retrieve site-specific Ångström exponents (AAEs) and mass absorption cross sections (MACs) for BC. An “aethalometer model” that used those values showed that biomass burning had a larger contribution to BC mass than fossil fuels (BCbiomass=57 % versus BCfossil=43 %). The potential source contribution function indicated that BCbiomass was transported to the site from northeastern India and northern Burma. The Weather Research and Forecasting model coupled with chemistry (WRF-Chem) indicated that 40 % of BCbiomass originated from Southeast Asia, while the high BCfossil was transported from the southwest of the sampling site. A radiative transfer model indicated that the average atmospheric direct radiative effect (DRE) of BC was +4.6 ± 2.4 W m−2, with +2.5 ± 1.8 W m−2 from BCbiomass and +2.1 ± 0.9 W m−2 from BCfossil. The DRE of BCbiomass and BCfossil produced heating rates of 0.07 ± 0.05 and 0.06 ± 0.02 K d−1, respectively. This study provides insights into sources of BC over a transport channel to the southeastern TP and the influence of the cross-border transportation of biomass-burning emissions from Southeast Asia during the pre-monsoon.
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He, Qianshan, Jianzhong Ma, Xiangdong Zheng, Xiaolu Yan, Holger Vömel, Frank G. Wienhold, Wei Gao, Dongwei Liu, Guangming Shi, and Tiantao Cheng. "Observational evidence of particle hygroscopic growth in the upper troposphere–lower stratosphere (UTLS) over the Tibetan Plateau." Atmospheric Chemistry and Physics 19, no. 13 (July 2, 2019): 8399–406. http://dx.doi.org/10.5194/acp-19-8399-2019.
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Abstract. We measured the vertical profiles of backscatter ratio (BSR) using the balloon-borne, lightweight Compact Optical Backscatter AerosoL Detector (COBALD) instruments above Linzhi, located in the southeastern Tibetan Plateau, in the summer of 2014. An enhanced aerosol layer in the upper troposphere–lower stratosphere (UTLS), with BSR (455 nm) > 1.1 and BSR (940 nm) > 1.4, was observed. The color index (CI) of the enhanced aerosol layer, defined as the ratio of aerosol backscatter ratios (ABSRs) at wavelengths of 940 and 455 nm, varied from 4 to 8, indicating the prevalence of fine particles with a mode radius of less than 0.1 µm. We find that unlike the very small particles (mode radius smaller than 0.04 µm) at low relative humidity (RHi < 40 %), the relatively large particles in the aerosol layer were generally very hydrophilic as their size increased dramatically with relative humidity. This result indicates that water vapor can play a very important role in increasing the size of fine particles in the UTLS over the Tibetan Plateau. Our observations provide observation-based evidence supporting the idea that aerosol particle hygroscopic growth is an important factor influencing the radiative properties of the Asian Tropopause Aerosol Layer (ATAL) during the Asian summer monsoon.
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Zhang, L., D. K. Henze, G. A. Grell, G. R. Carmichael, N. Bousserez, Q. Zhang, O. Torres, et al. "Constraining black carbon aerosol over Asia using OMI aerosol absorption optical depth and the adjoint of GEOS-Chem." Atmospheric Chemistry and Physics 15, no. 18 (September 17, 2015): 10281–308. http://dx.doi.org/10.5194/acp-15-10281-2015.
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Abstract. Accurate estimates of the emissions and distribution of black carbon (BC) in the region referred to here as Southeastern Asia (70–150° E, 11° S–55° N) are critical to studies of the atmospheric environment and climate change. Analysis of modeled BC concentrations compared to in situ observations indicates levels are underestimated over most of Southeast Asia when using any of four different emission inventories. We thus attempt to reduce uncertainties in BC emissions and improve BC model simulations by developing top-down, spatially resolved, estimates of BC emissions through assimilation of OMI (Ozone Monitoring Instrument) observations of aerosol absorption optical depth (AAOD) with the GEOS-Chem (Goddard Earth Observing System – chemistry) model and its adjoint for April and October 2006. Overwhelming enhancements, up to 500 %, in anthropogenic BC emissions are shown after optimization over broad areas of Southeast Asia in April. In October, the optimization of anthropogenic emissions yields a slight reduction (1–5 %) over India and parts of southern China, while emissions increase by 10–50 % over eastern China. Observational data from in situ measurements and AERONET (Aerosol Robotic Network) observations are used to evaluate the BC inversions and assess the bias between OMI and AERONET AAOD. Low biases in BC concentrations are improved or corrected in most eastern and central sites over China after optimization, while the constrained model still underestimates concentrations in Indian sites in both April and October, possibly as a consequence of low prior emissions. Model resolution errors may contribute up to a factor of 2.5 to the underestimation of surface BC concentrations over northern India. We also compare the optimized results using different anthropogenic emission inventories and discuss the sensitivity of top-down constraints on anthropogenic emissions with respect to biomass burning emissions. In addition, the impacts of brown carbon, the formulation of the observation operator, and different a priori constraints on the optimization are investigated. Overall, despite these limitations and uncertainties, using OMI AAOD to constrain BC sources improves model representation of BC distributions, particularly over China.
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Zhao, Zhuzi, Qiyuan Wang, Li Li, Yongming Han, Zhaolian Ye, Siwatt Pongpiachan, Yong Zhang, Suixin Liu, Ruixia Tian, and Junji Cao. "Characteristics of PM2.5 at a High-Altitude Remote Site in the Southeastern Margin of the Tibetan Plateau in Premonsoon Season." Atmosphere 10, no. 11 (October 25, 2019): 645. http://dx.doi.org/10.3390/atmos10110645.
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The Tibetan Plateau (TP) is one of the world’s most sensitive areas for climate change. Previous studies have revealed that air pollutants emitted from South and Southeast Asia can be transported to and have a negative impact on the TP. However, the majority of the investigators have focused on the pollutant transport processes from South Asian regions (i.e., India and Bangladesh) and parts of Southeast Asia, while the regions adjacent to the southeast fringe of the TP (i.e., Burma and the Sino-Burmese border) have been neglected. Here, fine particulate matter (PM2.5) samples were collected during the period 11 March to 13 May 2018 at Gaomeigu, a high-altitude remote site in the southeastern margin of the TP. Characteristics, sources of PM2.5, and the potential source regions for different chemical components were investigated. During the sampling time, PM2.5 mass loadings ranged from 3.79 to 54.57 µg m−3, with an arithmetic mean concentration of 20.99 ± 9.80 µg m−3. In general, major peaks of organic carbon (OC) and elemental carbon (EC) always coincided with high loadings of K+ and NO3−, which implies that common combustion sources caused these species’ concentrations to covary, while the daily variations of crustal elements showed different trends with the other chemical compositions, suggesting different source regions for crustal materials. Five source factors were identified as possible aerosol sources for PM2.5 by positive matrix factorization (PMF). They are the mining industry (5.3%), characterized by heavy metal elements; secondary formation (18.8%), described by the high concentrations of NH4+ and SO42−; traffic-related emissions (26.7%), dominated by carbonaceous species (especially soot-EC) and some metal elements; fugitive dust (15.2%), represented by crustal elements (Ti, Fe, and Mn), Ca2+, and Mg2+; and biomass burning (34.0%), which is typified by high concentrations of K+, NO3−, char-EC, primary OC, and secondary OC. The concentration-weighted trajectory (CWT) analysis results showed that the northeast part of Burma is the potential source region for high concentrations of EC and NO3− due to biomass burning emissions, while the tourism industry surrounding Gaomeigu gave strong grid cell values of SO42− as well as moderate values of EC and NO3−. Moreover, the mining industry in the southwest direction of Gaomeigu has important impacts on the zinc concentrations.
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Engling, Guenter, Yi-Nan Zhang, Chuen-Yu Chan, Xue-Fang Sang, Mang Lin, Kin-Fai Ho, Yok-Sheung Li, Chuan-Yao Lin, and James J. Lee. "Characterization and sources of aerosol particles over the southeastern Tibetan Plateau during the Southeast Asia biomass-burning season." Tellus B: Chemical and Physical Meteorology 63, no. 1 (January 2011): 117–28. http://dx.doi.org/10.1111/j.1600-0889.2010.00512.x.
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Li, J., B. E. Carlson, and A. A. Lacis. "Application of spectral analysis techniques to the intercomparison of aerosol data – Part 4: Synthesized analysis of multisensor satellite and ground-based AOD measurements using combined maximum covariance analysis." Atmospheric Measurement Techniques 7, no. 8 (August 14, 2014): 2531–49. http://dx.doi.org/10.5194/amt-7-2531-2014.
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Abstract. In this paper, we introduce the usage of a newly developed spectral decomposition technique – combined maximum covariance analysis (CMCA) – in the spatiotemporal comparison of four satellite data sets and ground-based observations of aerosol optical depth (AOD). This technique is based on commonly used principal component analysis (PCA) and maximum covariance analysis (MCA). By decomposing the cross-covariance matrix between the joint satellite data field and Aerosol Robotic Network (AERONET) station data, both parallel comparison across different satellite data sets and the evaluation of the satellite data against the AERONET measurements are simultaneously realized. We show that this new method not only confirms the seasonal and interannual variability of aerosol optical depth, aerosol-source regions and events represented by different satellite data sets, but also identifies the strengths and weaknesses of each data set in capturing the variability associated with sources, events or aerosol types. Furthermore, by examining the spread of the spatial modes of different satellite fields, regions with the largest uncertainties in aerosol observation are identified. We also present two regional case studies that respectively demonstrate the capability of the CMCA technique in assessing the representation of an extreme event in different data sets, and in evaluating the performance of different data sets on seasonal and interannual timescales. Global results indicate that different data sets agree qualitatively for major aerosol-source regions. Discrepancies are mostly found over the Sahel, India, eastern and southeastern Asia. Results for eastern Europe suggest that the intense wildfire event in Russia during summer 2010 was less well-represented by SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and OMI (Ozone Monitoring Instrument), which might be due to misclassification of smoke plumes as clouds. Analysis for the Indian subcontinent shows that here SeaWiFS agrees best with AERONET in terms of seasonality for both the Gangetic Basin and southern India, while on interannual timescales it has the poorest agreement.
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Dong, Xinyi, Joshua S. Fu, Qingzhao Zhu, Jian Sun, Jiani Tan, Terry Keating, Takashi Sekiya, et al. "Long-range transport impacts on surface aerosol concentrations and the contributions to haze events in China: an HTAP2 multi-model study." Atmospheric Chemistry and Physics 18, no. 21 (October 30, 2018): 15581–600. http://dx.doi.org/10.5194/acp-18-15581-2018.
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Abstract. Haze has been severely affecting the densely populated areas in China recently. While many of the efforts have been devoted to investigating the impact of local anthropogenic emission, limited attention has been paid to the contribution from long-range transport. In this study, we apply simulations from six participating models supplied through the Task Force on Hemispheric Transport of Air Pollution phase 2 (HTAP2) exercise to investigate the long-range transport impact of Europe (EUR) and Russia–Belarus–Ukraine (RBU) on the surface air quality in eastern Asia (EAS), with special focus on their contributions during the haze episodes in China. The impact of 20 % anthropogenic emission perturbation from the source region is extrapolated by a factor of 5 to estimate the full impact. We find that the full impacts from EUR and RBU are 0.99 µg m−3 (3.1 %) and 1.32 µg m−3 (4.1 %) during haze episodes, while the annual averaged full impacts are only 0.35 µg m−3 (1.7 %) and 0.53 µg m−3 (2.6 %). By estimating the aerosol response within and above the planetary boundary layer (PBL), we find that long-range transport from EUR within the PBL contributes to 22–38 % of the total column density of aerosol response in EAS. Comparison with the HTAP phase 1 (HTAP1) assessment reveals that from 2000 to 2010, the long-range transport from Europe to eastern Asia has decreased significantly by a factor of 2–10 for surface aerosol mass concentration due to the simultaneous emission reduction in source regions and emission increase in the receptor region. We also find the long-range transport from the Europe and RBU regions increases the number of haze events in China by 0.15 % and 0.11 %, and the North China Plain and southeastern China has 1–3 extra haze days (<3 %). This study is the first investigation into the contribution of long-range transport to haze in China with multi-model experiments.
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Zeng, Liangying, Yang Yang, Hailong Wang, Jing Wang, Jing Li, Lili Ren, Huimin Li, Yang Zhou, Pinya Wang, and Hong Liao. "Intensified modulation of winter aerosol pollution in China by El Niño with short duration." Atmospheric Chemistry and Physics 21, no. 13 (July 15, 2021): 10745–61. http://dx.doi.org/10.5194/acp-21-10745-2021.
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Abstract. El Niño–Southern Oscillation (ENSO), a phenomenon of periodic changes in sea surface temperature in the equatorial central-eastern Pacific Ocean, is the strongest signal of interannual variability in the climate system with a quasi-period of 2–7 years. El Niño events have been shown to have important influences on meteorological conditions in China. In this study, the impacts of El Niño with different durations on aerosol concentrations and haze days during December–January–February (DJF) in China are quantitatively examined using the state-of-the-art Energy Exascale Earth System Model version 1 (E3SMv1). We find that PM2.5 concentrations are increased by 1–2 µg m−3 in northeastern and southern China and decreased by up to 2.4 µg m−3 in central-eastern China during El Niño events relative to the climatological means. Compared to long-duration (LD) El Niño events, El Niño with short duration (SD) but strong intensity causes northerly wind anomalies over central-eastern China, which is favorable for aerosol dispersion over this region. Moreover, the anomalous southeasterly winds weaken the wintertime prevailing northwesterly in northeastern China and facilitate aerosol transport from southern and southeast Asia, enhancing aerosol increase in northeastern China during SD El Niño events relative to LD El Niño events. In addition, the modulation effect on haze days by SD El Niño events is 2–3 times more than that by LD El Niño events in China. The aerosol variations during El Niño events are mainly controlled by anomalous aerosol accumulation/dispersion and transport due to changes in atmospheric circulation, while El Niño-induced precipitation change has little effect. The occurrence frequency of SD El Niño events has been increasing significantly in recent decades, especially after the 1940s, suggesting that El Niño with short duration has exerted an increasingly intense modulation on aerosol pollution in China over the past few decades.
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Rosenfeld, D., G. Liu, X. Yu, Y. Zhu, J. Dai, X. Xu, and Z. Yue. "High-resolution (375 m) cloud microstructure as seen from the NPP/VIIRS satellite imager." Atmospheric Chemistry and Physics 14, no. 5 (March 10, 2014): 2479–96. http://dx.doi.org/10.5194/acp-14-2479-2014.
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Abstract. VIIRS (Visible Infrared Imaging Radiometer Suite), onboard the Suomi NPP (National Polar-orbiting Partnership) satellite, has an improved resolution of 750 m with respect to the 1000 m of the Moderate Resolution Imaging Spectroradiometer for the channels that allow retrieving cloud microphysical parameters such as cloud drop effective radius (re). VIIRS also has an imager with five channels of double resolution of 375 m, which was not designed for retrieving cloud products. A methodology for a high-resolution retrieval of re and microphysical presentation of the cloud field based on the VIIRS imager was developed and evaluated with respect to MODIS in this study. The tripled microphysical resolution with respect to MODIS allows obtaining new insights for cloud–aerosol interactions, especially at the smallest cloud scales, because the VIIRS imager can resolve the small convective elements that are sub-pixel for MODIS cloud products. Examples are given for new insights into ship tracks in marine stratocumulus, pollution tracks from point and diffused sources in stratocumulus and cumulus clouds over land, deep tropical convection in pristine air mass over ocean and land, tropical clouds that develop in smoke from forest fires and in heavy pollution haze over densely populated regions in southeastern Asia, and for pyro-cumulonimbus clouds. It is found that the VIIRS imager provides more robust physical interpretation and refined information for cloud and aerosol microphysics as compared to MODIS, especially in the initial stage of cloud formation. VIIRS is found to identify significantly more fully cloudy pixels when small boundary layer convective elements are present. This, in turn, allows for a better quantification of cloud–aerosol interactions and impacts on precipitation-forming processes.
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Tan, Tianyi, Min Hu, Zhuofei Du, Gang Zhao, Dongjie Shang, Jing Zheng, Yanhong Qin, et al. "Measurement report: Strong light absorption induced by aged biomass burning black carbon over the southeastern Tibetan Plateau in pre-monsoon season." Atmospheric Chemistry and Physics 21, no. 11 (June 7, 2021): 8499–510. http://dx.doi.org/10.5194/acp-21-8499-2021.
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Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by a factor of 13 and greatly elevated the number fraction of thickly coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell / core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation in the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction, and higher aging degree of BC particles in the upper atmosphere. Resulting from both increase in BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by a factor of 15, of which 21 % was contributed by the BC aging, and 79 % was contributed from the increase in BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.
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Umar, Muhammad, Salman Atif, Mark L. Hildebrandt, Ali Tahir, Muhammad Azmat, and Muhammad Zeeshan. "Trends of Aerosol Optical Thickness Using VIIRS S-NPP during Fog Episodes in Pakistan and India." Atmosphere 12, no. 2 (February 11, 2021): 242. http://dx.doi.org/10.3390/atmos12020242.
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Aerosol Optical Thickness (AOT) is one of the important parameters for assessing regional and global level of climate change. Fog episodes have considerably increased in south Asia because of environmental factors, and the burning of agricultural residue leads to major social and economic problems. In present study, Mann-Kendall trend analysis of AOT and active fire events was done, and their significance were assessed using long-term (October 2012–February 2020) remote sensing data derived smog maps. Visible Infrared Imaging Radiometer Suite National Polar Partnership (VIIRS N-PP) was used to map AOT episodes over the northern region of Pakistan and India. Results reveal that AOT displays a significantly decreasing trend over the northern and eastern region of Pakistan and a similar decreasing trend from the Western to Eastern region of India. Furthermore, active fire events have a significantly increasing trend at the Northern region of Pakistan. However, fire events have a significantly decreasing trend over the southern and southeastern region of India. Additionally, statistically significant decreasing trends were observed for AOT over Chakwal (p-value = 0.2, Z_MK = −2.3) and Patiala (p-value = 0.15, Z_MK = −3.2). Fire events have a significantly increasing trend for Dera Ismail Khan (p-value = 0.01, Z_MK = 1.9), Jhang (p-value = 0.01, Z_MK = 1.9), and Chakwal (p-value = 0.01, Z_MK = 1.8), while they are significantly decreasing trend near New Delhi (p-value = 0.2, Z_MK = −0.9), Aligarh (p-value = 0.15, Z_MK = −0.9) and Patiala (p-value = 0.2, Z_MK = −0.8).
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Su, Qin, and Buwen Dong. "Recent Decadal Changes in Heat Waves over China: Drivers and Mechanisms." Journal of Climate 32, no. 14 (June 20, 2019): 4215–34. http://dx.doi.org/10.1175/jcli-d-18-0479.1.
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Abstract Observational analysis indicates significant decadal changes in daytime, nighttime, and compound (both daytime and nighttime) heat waves (HWs) over China across the mid-1990s, featuring a rapid increase in frequency, intensity, and spatial extent. The variations of these observed decadal changes are assessed by the comparison between the present day (PD) of 1994–2011 and the early period (EP) of 1964–81. The compound HWs change most remarkably in all three aspects, with frequency averaged over China in the PD tripling that in the EP and intensity and spatial extent nearly doubling. The daytime and nighttime HWs also change significantly in all three aspects. A set of numerical experiments is used to investigate the drivers and physical processes responsible for the decadal changes of the HWs. Results indicate the predominant role of the anthropogenic forcing, including changes in greenhouse gas (GHG) concentrations and anthropogenic aerosol (AA) emissions in the HW decadal changes. The GHG changes have dominant impacts on the three types of HWs, while the AA changes make significant influences on daytime HWs. The GHG changes increase the frequency, intensity, and spatial extent of the three types of HWs over China both directly via the strengthened greenhouse effect and indirectly via land–atmosphere and circulation feedbacks in which GHG-change-induced warming in sea surface temperature plays an important role. The AA changes decrease the frequency and intensity of daytime HWs over Southeastern China through mainly aerosol–radiation interaction, but increase the frequency and intensity of daytime HWs over Northeastern China through AA-change-induced surface–atmosphere feedbacks and dynamical changes related to weakened East Asian summer monsoon.
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Itahashi, Syuichi, Rohit Mathur, Christian Hogrefe, Sergey L. Napelenok, and Yang Zhang. "Incorporation of volcanic SO<sub>2</sub> emissions in the Hemispheric CMAQ (H-CMAQ) version 5.2 modeling system and assessing their impacts on sulfate aerosol over the Northern Hemisphere." Geoscientific Model Development 14, no. 9 (September 16, 2021): 5751–68. http://dx.doi.org/10.5194/gmd-14-5751-2021.
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Abstract. The state-of-the-science Community Multiscale Air Quality (CMAQ) Modeling System has recently been extended for hemispheric-scale modeling applications (referred to as H-CMAQ). In this study, satellite-constrained estimation of the degassing SO2 emissions from 50 volcanoes over the Northern Hemisphere is incorporated into H-CMAQ, and their impact on tropospheric sulfate aerosol (SO42-) levels is assessed for 2010. The volcanic degassing improves predictions of observations from the Acid Deposition Monitoring Network in East Asia (EANET), the United States Clean Air Status and Trends Network (CASTNET), and the United States Integrated Monitoring of Protected Visual Environments (IMPROVE). Over Asia, the increased SO42- concentrations were seen to correspond to the locations of volcanoes, especially over Japan and Indonesia. Over the USA, the largest impacts that occurred over the central Pacific were caused by including the Hawaiian Kilauea volcano, while the impacts on the continental USA were limited to the western portion during summertime. The emissions of the Soufrière Hills volcano located on the island of Montserrat in the Caribbean Sea affected the southeastern USA during the winter season. The analysis at specific sites in Hawaii and Florida also confirmed improvements in regional performance for modeled SO42- by including volcanoes SO2 emissions. At the edge of the western USA, monthly averaged SO42- enhancements greater than 0.1 µg m−3 were noted within the boundary layer (defined as surface to 750 hPa) during June–September. Investigating the change on SO42- concentration throughout the free troposphere revealed that although the considered volcanic SO2 emissions occurred at or below the middle of free troposphere (500 hPa), compared to the simulation without the volcanic source, SO42- enhancements of more than 10 % were detected up to the top of the free troposphere (250 hPa). Our model simulations and comparisons with measurements across the Northern Hemisphere indicate that the degassing volcanic SO2 emissions are an important source and should be considered in air quality model simulations assessing background SO42- levels and their source attribution.
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Shang, Dongjie, Min Hu, Jing Zheng, Yanhong Qin, Zhuofei Du, Mengren Li, Jingyao Fang, et al. "Particle number size distribution and new particle formation under the influence of biomass burning at a high altitude background site at Mt. Yulong (3410 m), China." Atmospheric Chemistry and Physics 18, no. 21 (November 1, 2018): 15687–703. http://dx.doi.org/10.5194/acp-18-15687-2018.
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Abstract. Biomass burning (BB) activities have a great impact on the particle number size distribution (PNSD) in the upper troposphere of the Tibetan Plateau, which could affect regional and global climate. An intensive campaign focused on the measurement of the PNSD, gaseous pollutants, and meteorological parameters was conducted at Mt. Yulong, a high-altitude site (3410 m a.s.l.) on the southeastern Tibetan Plateau during the pre-monsoon season (22 March to 15 April). During this period, intensive BB activities in southern Asia were detected by fire maps. The long-range transport of BB pollutants can increase the accumulation mode particles in the background atmosphere at Mt. Yulong. As a consequence, the cloud condensation nuclei (CCN) concentration was found to be 2–8 times higher during BB periods than during clean periods. Apart from BB, variations of the planet boundary layer (PBL) and new particle formation (NPF) were other factors that influenced the PNSD. However, only three NPF events (with a frequency of 14 %) were observed at Mt. Yulong. The occurrence of NPF events during clean episodes corresponded to an elevated PBL or transported BB pollutants. Due to the lack of condensable vapors including sulfuric acid and organic compounds, the newly formed particles were not able to grow to CCN size. Our study emphasizes the influences of BB on the aerosol and CCN concentration in the atmosphere of the Tibetan Plateau. These results also have the potential to improve our understanding of the variation of the particle concentration in the upper troposphere, and provide information for regional and global climate models.
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Shen, X. J., J. Y. Sun, Y. M. Zhang, B. Wehner, A. Nowak, T. Tuch, X. C. Zhang, et al. "First long-term study of particle number size distributions and new particle formation events of regional aerosol in the North China Plain." Atmospheric Chemistry and Physics Discussions 10, no. 10 (October 28, 2010): 25205–42. http://dx.doi.org/10.5194/acpd-10-25205-2010.
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Abstract. Atmospheric particle number size distributions (size range 0.003–10 μm) were measured between March 2008 and August 2009 at Shangdianzi (SDZ), a rural research station in the North China Plain. These measurements were made in an attempt to better characterize the tropospheric background aerosol in Northern China, one of the currently more polluted regions of the globe. The mean particle number concentrations of the total aerosol, as well as the nucleation, Aitken and accumulation modes were determined to 1.2±0.9×104, 3.6±7.9×103, 4.4±3.4×103 and 3.5±2.8×103 cm−3, respectively. A general finding is that the particle number concentrations were higher during spring compared to the other seasons. The air mass origin had an important effect on the particle number concentration and new particle formation events. Air masses from northwest (i.e. inner Asia) showed the highest concentrations of nucleation mode particles, while southeasterly air masses showed the highest concentrations of accumulation mode particles. Significant diurnal variations in particle number were observed, which could be linked to new particle formation events, i.e. gas-to-particle conversion. During particle formation events, the number concentration of the nucleation mode rose up to maximum values of 104 cm−3. New particle formation events were observed on 36% of the measurement days. The formation rate ranged between 0.7 and 72.7 cm−3 s−1, with a mean value of 8.0 cm−3 s−1. The values of the nucleation mode growth rate ranged between 0.3 and 14.5 nm h−1, with a mean value of 4.3 nm h−1. It is an essential observation that on many occasions, the nucleation mode was able to grow into the size of cloud condensation nuclei (CCN) within a matter of several hours. Furthermore, the new particle formation were usually followed by a measurable increase in total particle mass concentration and extinction coefficient, indicative of a high abundance of condensable vapors in the atmosphere under study.
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Zhang, Yang, Chinmay Jena, Kai Wang, Clare Paton-Walsh, Élise-Andrée Guérette, Steven Utembe, Jeremy David Silver, and and Melita Keywood. "Multiscale Applications of Two Online-Coupled Meteorology-Chemistry Models during Recent Field Campaigns in Australia, Part I: Model Description and WRF/Chem-ROMS Evaluation Using Surface and Satellite Data and Sensitivity to Spatial Grid Resolutions." Atmosphere 10, no. 4 (April 8, 2019): 189. http://dx.doi.org/10.3390/atmos10040189.
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Air pollution and associated human exposure are important research areas in Greater Sydney, Australia. Several field campaigns were conducted to characterize the pollution sources and their impacts on ambient air quality including the Sydney Particle Study Stages 1 and 2 (SPS1 and SPS2), and the Measurements of Urban, Marine, and Biogenic Air (MUMBA). In this work, the Weather Research and Forecasting model with chemistry (WRF/Chem) and the coupled WRF/Chem with the Regional Ocean Model System (ROMS) (WRF/Chem-ROMS) are applied during these field campaigns to assess the models’ capability in reproducing atmospheric observations. The model simulations are performed over quadruple-nested domains at grid resolutions of 81-, 27-, 9-, and 3-km over Australia, an area in southeastern Australia, an area in New South Wales, and the Greater Sydney area, respectively. A comprehensive model evaluation is conducted using surface observations from these field campaigns, satellite retrievals, and other data. This paper evaluates the performance of WRF/Chem-ROMS and its sensitivity to spatial grid resolutions. The model generally performs well at 3-, 9-, and 27-km resolutions for sea-surface temperature and boundary layer meteorology in terms of performance statistics, seasonality, and daily variation. Moderate biases occur for temperature at 2-m and wind speed at 10-m in the mornings and evenings due to the inaccurate representation of the nocturnal boundary layer and surface heat fluxes. Larger underpredictions occur for total precipitation due to the limitations of the cloud microphysics scheme or cumulus parameterization. The model performs well at 3-, 9-, and 27-km resolutions for surface O3 in terms of statistics, spatial distributions, and diurnal and daily variations. The model underpredicts PM2.5 and PM10 during SPS1 and MUMBA but overpredicts PM2.5 and underpredicts PM10 during SPS2. These biases are attributed to inaccurate meteorology, precursor emissions, insufficient SO2 conversion to sulfate, inadequate dispersion at finer grid resolutions, and underprediction in secondary organic aerosol. The model gives moderate biases for net shortwave radiation and cloud condensation nuclei but large biases for other radiative and cloud variables. The performance of aerosol optical depth and latent/sensible heat flux varies for different simulation periods. Among all variables evaluated, wind speed at 10-m, precipitation, surface concentrations of CO, NO, NO2, SO2, O3, PM2.5, and PM10, aerosol optical depth, cloud optical thickness, cloud condensation nuclei, and column NO2 show moderate-to-strong sensitivity to spatial grid resolutions. The use of finer grid resolutions (3- or 9-km) can generally improve the performance for those variables. While the performance for most of these variables is consistent with that over the U.S. and East Asia, several differences along with future work are identified to pinpoint reasons for such differences.
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Wu, Jiarui, Naifang Bei, Xia Li, Junji Cao, Tian Feng, Yichen Wang, Xuexi Tie, and Guohui Li. "Widespread air pollutants of the North China Plain during the Asian summer monsoon season: a case study." Atmospheric Chemistry and Physics 18, no. 12 (June 18, 2018): 8491–504. http://dx.doi.org/10.5194/acp-18-8491-2018.
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Abstract. During the Asian summer monsoon season, prevailing southeasterly–southwesterly winds are subject to delivering air pollutants from the North China Plain (NCP) to northeast and northwest China. In the present study, the WRF-CHEM model is used to evaluate contributions of trans-boundary transport of NCP emissions to the air quality in northeast and northwest China during a persistent air pollution episode from 22 to 28 May 2015. The WRF-CHEM model generally performs well in capturing the observed temporal variation and spatial distribution of fine particulate matter (PM2.5), ozone (O3), and NO2. The simulated temporal variation of aerosol species is also in good agreement with measurements in Beijing during the episode. Model simulations show that NCP emissions contribute substantially to the PM2.5 level in Liaoning and Shanxi provinces, the adjacent downwind areas of the NCP, with an average of 24.2 and 13.9 µg m−3 during the episode, respectively. The PM2.5 contributions in Jilin and Shaanxi provinces are also appreciable, with an average of 9.6 and 6.5 µg m−3, respectively. The average percentage contributions of NCP emissions to the PM2.5 level in Liaoning, Jilin, Shanxi, and Shaanxi provinces are 40.6, 27.5, 32.2, and 20.9 %, respectively. The NCP emissions contribute remarkably to the O3 level in Liaoning province, with an average of 46.5 µg m−3, varying from 23.9 to 69.5 µg m−3. The O3 level in Shanxi province is also influenced considerably by NCP emissions, with an average contribution of 35.1 µg m−3. The O3 level in Shanxi province is also influenced considerably by NCP emissions, with an average contribution of 35.1 µg m−3. The average O3 contributions of NCP emissions to Jilin and Shaanxi provinces are 28.7 and 20.7 µg m−3, respectively. The average percentage contributions of NCP emissions to the afternoon O3 level in Liaoning, Jilin, Shanxi, and Shaanxi provinces are 27.4, 19.5, 21.2, and 15.8 %, respectively. However, the effect of NCP emissions on the air quality in Inner Mongolia is generally insignificant. Therefore, effective mitigation of NCP emissions not only improves the local air quality, but is also beneficial to the air quality in northeast and northwest China during the Asian summer monsoon season.
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Ding, Ke, Xin Huang, Aijun Ding, Minghuai Wang, Hang Su, Veli-Matti Kerminen, Tuukka Petäjä, et al. "Aerosol-boundary-layer-monsoon interactions amplify semi-direct effect of biomass smoke on low cloud formation in Southeast Asia." Nature Communications 12, no. 1 (November 5, 2021). http://dx.doi.org/10.1038/s41467-021-26728-4.
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AbstractLow clouds play a key role in the Earth-atmosphere energy balance and influence agricultural production and solar-power generation. Smoke aloft has been found to enhance marine stratocumulus through aerosol-cloud interactions, but its role in regions with strong human activities and complex monsoon circulation remains unclear. Here we show that biomass burning aerosols aloft strongly increase the low cloud coverage over both land and ocean in subtropical southeastern Asia. The degree of this enhancement and its spatial extent are comparable to that in the Southeast Atlantic, even though the total biomass burning emissions in Southeast Asia are only one-fifth of those in Southern Africa. We find that a synergetic effect of aerosol-cloud-boundary layer interaction with the monsoon is the main reason for the strong semi-direct effect and enhanced low cloud formation in southeastern Asia.
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Fan, Xuehua, Xiangao Xia, Hongbin Chen, Yanliang Zhu, Jun Li, Honglong Yang, and Hongyan Luo. "Baseline of Surface and Column-Integrated Aerosol Loadings in the Pearl River Delta Region, China." Frontiers in Environmental Science 10 (May 30, 2022). http://dx.doi.org/10.3389/fenvs.2022.893408.
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Much attention has been paid to the rapid variation of aerosol loading in the urban areas of the Pearl River Delta (PRD) region. The baseline of aerosol loading in this rapidly developing region is critical in evaluating how and why the aerosol level has evolved, which absolutely requires long-term observations. Based on long-term observations of aerosol optical depth (AOD), visibility, and particulate matter (PM) mass concentrations at Xichong (114.56°E, 22.49°N), a background site in the PRD region, the variabilities of aerosol loading at multiple temporal scales are revealed. The means (±σ) of AOD, visibility, PM10, PM2.5, and PM1 are 0.38 ± 0.07, 12.6 ± 2.3 km, 23.7 ± 12.6 μg/m3, 19.7 ± 11.0 μg/m3, and 16.1 ± 10.1 μg/m3, respectively, which show that aerosol loading at the Xichong site is much lower than that in urban and suburban sites. Significant decreases in PM10, PM2.5, and PM1 mass concentrations are observed with magnitudes up to −2.13, −1.82, and −1.37 yr−1, respectively, at a 95% confidence level. The decrease in aerosol loadings at Xichong is attributed to the strict environmental regulations for improving air quality. Higher AOD and PM (lower visibility) values are observed during the early spring months as a result of long-range transport of biomass burning from Southeastern Asia. Diurnal variations of PM and visibility are dominantly determined by those of boundary layer height and relative humidity. PM mass concentrations show a generally negative (positive) correlation with visibility (AOD) at Xichong, but the correlations are weak with the R2 of 0.22 and 0.54, respectively. Low visibility and high aerosol loading are generally associated with very weak easterly and southerly winds. Understanding of variability of surface particle concentration and column-integrated aerosol loading at this background site in the PRD region would provide a scientific basis for the adoption of pollution prevention and control measures.
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Engling, Guenter, Yi-Nan Zhang, Chuen-Yu Chan, Xue-Fang Sang, Mang Lin, Kin-Fai Ho, Yok-Sheung Li, Chuan-Yao Lin, and James J. Lee. "Characterization and sources of aerosol particles over the southeastern Tibetan Plateau during the Southeast Asia biomass-burning season." Tellus B 63, no. 1 (February 1, 2011). http://dx.doi.org/10.3402/tellusb.v63i1.16193.
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