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Zhang J, Gong X, Crosbie E, Diskin G, Froyd K, Hall S, Kupc A, Moore R, Peischl J, Rollins A, Schwarz J, Shook M, Thompson C, Ullmann K, Williamson C, Wisthaler A, Xu L, Ziemba L, Brock CA, Wang J. Stratospheric air intrusions promote global-scale new particle formation. Science 2024; 385:210-216. [PMID: 38991080 DOI: 10.1126/science.adn2961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 05/13/2024] [Indexed: 07/13/2024]
Abstract
New particle formation in the free troposphere is a major source of cloud condensation nuclei globally. The prevailing view is that in the free troposphere, new particles are formed predominantly in convective cloud outflows. We present another mechanism using global observations. We find that during stratospheric air intrusion events, the mixing of descending ozone-rich stratospheric air with more moist free tropospheric background results in elevated hydroxyl radical (OH) concentrations. Such mixing is most prevalent near the tropopause where the sulfur dioxide (SO2) mixing ratios are high. The combination of elevated SO2 and OH levels leads to enhanced sulfuric acid concentrations, promoting particle formation. Such new particle formation occurs frequently and over large geographic regions, representing an important particle source in the midlatitude free troposphere.
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Affiliation(s)
- Jiaoshi Zhang
- Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Xianda Gong
- Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Ewan Crosbie
- NASA Langley Research Center, Hampton, VA, USA
- Science Systems and Applications, Inc., Hampton, VA, USA
| | | | - Karl Froyd
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
| | - Samuel Hall
- Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - Agnieszka Kupc
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
- Faculty of Physics, Aerosol Physics and Environmental Physics, University of Vienna, Vienna, Austria
| | | | - Jeff Peischl
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
| | - Andrew Rollins
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
| | - Joshua Schwarz
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
| | | | - Chelsea Thompson
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
| | - Kirk Ullmann
- Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - Christina Williamson
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
- Climate Research Programme, Finnish Meteorological Institute, Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, Finland
| | - Armin Wisthaler
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria
- Department of Chemistry, University of Oslo, Oslo, Norway
| | - Lu Xu
- Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Luke Ziemba
- NASA Langley Research Center, Hampton, VA, USA
| | - Charles A Brock
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
| | - Jian Wang
- Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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2
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Pan LL, Atlas EL, Honomichl SB, Smith WP, Kinnison DE, Solomon S, Santee ML, Saiz-Lopez A, Laube JC, Wang B, Ueyama R, Bresch JF, Hornbrook RS, Apel EC, Hills AJ, Treadaway V, Smith K, Schauffler S, Donnelly S, Hendershot R, Lueb R, Campos T, Viciani S, D’Amato F, Bianchini G, Barucci M, Podolske JR, Iraci LT, Gurganus C, Bui P, Dean-Day JM, Millán L, Ryoo JM, Barletta B, Koo JH, Kim J, Liang Q, Randel WJ, Thornberry T, Newman PA. East Asian summer monsoon delivers large abundances of very-short-lived organic chlorine substances to the lower stratosphere. Proc Natl Acad Sci U S A 2024; 121:e2318716121. [PMID: 38483991 PMCID: PMC10962947 DOI: 10.1073/pnas.2318716121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 02/12/2024] [Indexed: 03/27/2024] Open
Abstract
Deep convection in the Asian summer monsoon is a significant transport process for lifting pollutants from the planetary boundary layer to the tropopause level. This process enables efficient injection into the stratosphere of reactive species such as chlorinated very-short-lived substances (Cl-VSLSs) that deplete ozone. Past studies of convective transport associated with the Asian summer monsoon have focused mostly on the south Asian summer monsoon. Airborne observations reported in this work identify the East Asian summer monsoon convection as an effective transport pathway that carried record-breaking levels of ozone-depleting Cl-VSLSs (mean organic chlorine from these VSLSs ~500 ppt) to the base of the stratosphere. These unique observations show total organic chlorine from VSLSs in the lower stratosphere over the Asian monsoon tropopause to be more than twice that previously reported over the tropical tropopause. Considering the recently observed increase in Cl-VSLS emissions and the ongoing strengthening of the East Asian summer monsoon under global warming, our results highlight that a reevaluation of the contribution of Cl-VSLS injection via the Asian monsoon to the total stratospheric chlorine budget is warranted.
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Affiliation(s)
- Laura L. Pan
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Elliot L. Atlas
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
| | - Shawn B. Honomichl
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Warren P. Smith
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Douglas E. Kinnison
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Susan Solomon
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Michelle L. Santee
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA91109
| | - Alfonso Saiz-Lopez
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Blas Cabrera, The Spanish National Research Council (CSIC), Madrid28006, Spain
| | - Johannes C. Laube
- Institute for Energy and Climate Research (IEK-7), Forschungszentrum Jülich, Jülich52425, Germany
| | - Bin Wang
- Department of Atmospheric Sciences and International Pacific Research Center, The University of Hawaii, Honolulu, HI96822
| | - Rei Ueyama
- NASA Ames Research Center, Moffett Field, CA94035
| | - James F. Bresch
- Mesoscale and Microscale Meteorology Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Rebecca S. Hornbrook
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Eric C. Apel
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Alan J. Hills
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Victoria Treadaway
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO80309
- National Oceanic and Atmospheric Administration Chemical Sciences Laboratory, Boulder, CO80305
| | - Katie Smith
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
| | - Sue Schauffler
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
| | - Stephen Donnelly
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
- Department of Chemistry, Fort Hays State University, Hays, KS67601
| | - Roger Hendershot
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
| | - Richard Lueb
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
- Rosenstiel School of Marine, Earth, and Atmospheric Science, Department of Atmospheric Sciences, University of Miami, Miami, FL33149
| | - Teresa Campos
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Silvia Viciani
- National Institute of Optics, National Research Council, Sesto Fiorentino50019, Italy
| | - Francesco D’Amato
- National Institute of Optics, National Research Council, Sesto Fiorentino50019, Italy
| | - Giovanni Bianchini
- National Institute of Optics, National Research Council, Sesto Fiorentino50019, Italy
| | - Marco Barucci
- National Institute of Optics, National Research Council, Sesto Fiorentino50019, Italy
| | | | | | - Colin Gurganus
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO80309
- National Oceanic and Atmospheric Administration Chemical Sciences Laboratory, Boulder, CO80305
| | - Paul Bui
- NASA Ames Research Center, Moffett Field, CA94035
- Bay Area Environmental Research Institute, Moffett Field, CA94035
| | - Jonathan M. Dean-Day
- NASA Ames Research Center, Moffett Field, CA94035
- Bay Area Environmental Research Institute, Moffett Field, CA94035
| | - Luis Millán
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA91109
| | - Ju-Mee Ryoo
- NASA Ames Research Center, Moffett Field, CA94035
- Science and Technology Corporation, Moffett Field, CA94035
| | - Barbara Barletta
- Department of Chemistry, University of California Irvine, Irvine, CA92697
| | - Ja-Ho Koo
- Department of Atmospheric Sciences, Yonsei University, Seoul03722, Republic of Korea
| | - Joowan Kim
- Department of Atmospheric Science, Kongju National University, Gongju32588, Republic of Korea
| | - Qing Liang
- NASA Goddard Space Flight Center, Greenbelt, MD20771
| | - William J. Randel
- Atmospheric Chemistry Observations and Modeling Laboratory, NSF National Center for Atmospheric Research, Boulder, CO80301
| | - Troy Thornberry
- National Oceanic and Atmospheric Administration Chemical Sciences Laboratory, Boulder, CO80305
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Bagaria P, Mahapatra PS, Bherwani H, Pandey R. Environmental management: a country-level evaluation of atmospheric particulate matter removal by the forests of India. ENVIRONMENTAL MONITORING AND ASSESSMENT 2023; 195:1306. [PMID: 37828295 DOI: 10.1007/s10661-023-11928-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 09/30/2023] [Indexed: 10/14/2023]
Abstract
Particulate matter (PM) is a critical air pollutant, responsible for an array of ailments leading to premature mortality worldwide. Nature-based solutions for mitigation of PM and especially role of forests in mitigating PM from an ecosystem perspective are less explored. Forests provide a natural pollution abatement strategy by providing a surface area for the deposition of PM. Depending on their structure and composition, forests have varying capacities for PM adsorption, which is again less explored. Hence, in the present study, we evaluate the removal capacity of PM by the forest-type groups of India. Deposition flux and total PM removal across sixteen forest types were estimated based on the 2019 dataset of PM using Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) data. Externality values and PM removal costs by industrial equipment were used for associating an economic value to the air pollution abatement service by forests. The total PM2.5 removal by forests in 2019 was estimated to be 1361.28 tons and PM10 was estimated to be 303,658.27 tons. Deposition of PM was found to be high in littoral and swamp forests, tropical semi-evergreen forests, tropical moist deciduous forests, and sub-tropical pine forests. Tropical dry deciduous forests had the highest net weight % removal of PM with 39% removal for PM2.5 and 39% removal for PM10. The air pollution abatement service by forests for PM removal was 188 M US dollars (USD) with externality-based removal service by forests of 2009 M USD. The net PM removed by all forests of India was estimated to be approximately worth ₹ 470-648 Crore (59-81 million dollars) for PM2.5 and worth ₹56,746-1,22,617 Crore (7093-15,327 million dollars) for PM10 based on valuation using value transfer method. The study concludes that forests can be a significant contributor to PM reduction at a global level. Especially for India's National Clean Air Programme and further research and policy considerations, the findings would be extremely useful.
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Affiliation(s)
| | | | | | - Rajiv Pandey
- Indian Council of Forestry Research and Education, Dehradun, India.
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4
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Goetz JD, Giordano MR, Stockwell CE, Bhave PV, Puppala PS, Panday AK, Jayarathne T, Stone EA, Yokelson RJ, DeCarlo PF. Aerosol Mass Spectral Profiles from NAMaSTE Field-Sampled South Asian Combustion Sources. ACS EARTH & SPACE CHEMISTRY 2022; 6:2619-2631. [PMID: 36425341 PMCID: PMC9677502 DOI: 10.1021/acsearthspacechem.2c00173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 09/28/2022] [Accepted: 10/06/2022] [Indexed: 06/16/2023]
Abstract
Unit mass resolution mass spectral profiles of nonrefractory submicron aerosol were retrieved from undersampled atmospheric emission sources common to South Asia using a "mini" aerosol mass spectrometer. Emission sources including wood- and dung-fueled cookstoves, agricultural residue burning, garbage burning, engine exhaust, and coal-fired brick kilns were sampled during the 2015 Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) campaign. High-resolution peak fitting estimates of the mass spectra were used to characterize ions found within each source profile and help identify mass spectral signatures unique to aerosol emissions from the investigated source types. The first aerosol mass spectral profiles of dung burning, charcoal burning, garbage burning, and brick kilns are provided in this work. The online aerosol mass spectra show that organics were generally the dominant component of the nonrefractory aerosol. However, inorganic aerosol components including ammonium and chloride were significant in dung- and charcoal-fired cookstove emissions and sulfate compounds were major components of the coal-fired brick kiln emissions. Organic mass spectra from both the charcoal burning and zigzag brick kiln were dominated by nitrogen-containing ions thought to be from the electron ionization of amines and amides contained in the emissions. The mixed garbage burning emissions profiles were dominated by plastic combustion with very low fractions of organic markers associated with biomass burning. The plastic burning emissions were associated with enhanced organic signal at mass-to-charge (m/z) 104 and m/z 166, which could be useful fragment ion indicators for garbage burning in ambient aerosol profiles. Finally, a framework for the identification of emission sources using the unit mass resolution organic mass fractions at m/z 55 (f 55), m/z 57 (f 57), and m/z 60 (f 60) is proposed in this work. Plotting the ratio of f 55 to f 57 versus f 60 is found to be effective for the identification of emissions by the fuel type and even useful in separating emissions of similar source types. Although the sample size was limited, these results give further context to the aerosol and gas-phase emission factors presented in other NAMaSTE works and provide a critical reference for future aerosol composition measurements in South Asia.
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Affiliation(s)
- J. Douglas Goetz
- Laboratory
for Atmospheric and Space Physics, University
of Colorado at Boulder, Boulder, Colorado 80303, United States
| | - Michael R. Giordano
- Department
of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Chelsea E. Stockwell
- Department
of Chemistry, University of Montana, Missoula, Montana 59812, United States
| | - Prakash V. Bhave
- International
Centre for Integrated Mountain Development (ICIMOD), Lalitpur 44700, Nepal
| | - Praveen S. Puppala
- International
Centre for Integrated Mountain Development (ICIMOD), Lalitpur 44700, Nepal
| | - Arnico K. Panday
- International
Centre for Integrated Mountain Development (ICIMOD), Lalitpur 44700, Nepal
| | - Thilina Jayarathne
- Department
of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Elizabeth A. Stone
- Department
of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
- Department
of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States
| | - Robert J. Yokelson
- Department
of Chemistry, University of Montana, Missoula, Montana 59812, United States
| | - Peter F. DeCarlo
- Department
of Environmental Health and Engineering, Johns Hopkins University, Baltimore, Maryland 21205, United States
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5
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Favaretto C, Allegra M, Deco G, Metcalf NV, Griffis JC, Shulman GL, Brovelli A, Corbetta M. Subcortical-cortical dynamical states of the human brain and their breakdown in stroke. Nat Commun 2022; 13:5069. [PMID: 36038566 PMCID: PMC9424299 DOI: 10.1038/s41467-022-32304-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 07/25/2022] [Indexed: 11/17/2022] Open
Abstract
The mechanisms controlling dynamical patterns in spontaneous brain activity are poorly understood. Here, we provide evidence that cortical dynamics in the ultra-slow frequency range (<0.01–0.1 Hz) requires intact cortical-subcortical communication. Using functional magnetic resonance imaging (fMRI) at rest, we identify Dynamic Functional States (DFSs), transient but recurrent clusters of cortical and subcortical regions synchronizing at ultra-slow frequencies. We observe that shifts in cortical clusters are temporally coincident with shifts in subcortical clusters, with cortical regions flexibly synchronizing with either limbic regions (hippocampus/amygdala), or subcortical nuclei (thalamus/basal ganglia). Focal lesions induced by stroke, especially those damaging white matter connections between basal ganglia/thalamus and cortex, provoke anomalies in the fraction times, dwell times, and transitions between DFSs, causing a bias toward abnormal network integration. Dynamical anomalies observed 2 weeks after stroke recover in time and contribute to explaining neurological impairment and long-term outcome. Favaretto et al. show that the brain rapidly alternates between transient connectivity patterns, with cortical regions flexibly synchronizing with two groups of subcortical regions, and that this dynamic is abnormal in stroke patients.
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Affiliation(s)
- Chiara Favaretto
- Padova Neuroscience Center (PNC), University of Padova, via Orus 2/B, 35129, Padova, Italy. .,Department of Neuroscience (DNS), University of Padova, via Giustiniani 2, 35128, Padova, Italy.
| | - Michele Allegra
- Padova Neuroscience Center (PNC), University of Padova, via Orus 2/B, 35129, Padova, Italy.,Department of Physics and Astronomy "Galileo Galilei", University of Padova, via Marzolo 8, 35131, Padova, Italy.,Institut de Neurosciences de la Timone UMR 7289, Aix Marseille Université, CNRS, 13005, Marseille, France
| | - Gustavo Deco
- Center for Brain and Cognition (CBC), Department of Information Technologies and Communications (DTIC), Pompeu Fabra University, Edifici Mercè Rodoreda, Carrer Trias i Fargas 25-27, 08005, Barcelona, Catalonia, Spain.,Institució Catalana de Recerca I Estudis Avançats (ICREA), Passeig Lluis Companys 23, 08010, Barcelona, Catalonia, Spain
| | - Nicholas V Metcalf
- Department of Neurology, Washington University School of Medicine, 660S. Euclid Ave, St. Louis, MO, 63110, USA
| | - Joseph C Griffis
- Department of Neurology, Washington University School of Medicine, 660S. Euclid Ave, St. Louis, MO, 63110, USA
| | - Gordon L Shulman
- Department of Neurology, Washington University School of Medicine, 660S. Euclid Ave, St. Louis, MO, 63110, USA.,Department of Radiology, Washington University School of Medicine, 660S. Euclid Ave, St. Louis, MO, 63110, USA
| | - Andrea Brovelli
- Institut de Neurosciences de la Timone UMR 7289, Aix Marseille Université, CNRS, 13005, Marseille, France
| | - Maurizio Corbetta
- Padova Neuroscience Center (PNC), University of Padova, via Orus 2/B, 35129, Padova, Italy. .,Department of Neuroscience (DNS), University of Padova, via Giustiniani 2, 35128, Padova, Italy. .,Department of Neurology, Washington University School of Medicine, 660S. Euclid Ave, St. Louis, MO, 63110, USA. .,Department of Radiology, Washington University School of Medicine, 660S. Euclid Ave, St. Louis, MO, 63110, USA. .,VIMM, Venetian Institute of Molecular Medicine (VIMM), Biomedical Foundation, via Orus 2, 35129, Padova, Italy.
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Stratospheric Chemical Lifetime of Aviation Fuel Incomplete Combustion Products. ATMOSPHERE 2022. [DOI: 10.3390/atmos13081209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The stratosphere contains haze rich in sulfuric acid, which plays a significant role in stratospheric chemistry and in global climate. Commercial aircraft deposit significant amounts of incomplete combustion products into the lower stratosphere. We have studied the stability of these incomplete combustion products to reaction with sulfuric acid, using a predictive model based on experimental reaction kinetics. We demonstrate that sulfuric acid chemistry is likely to be a significant component of the chemistry of organics in the stratosphere. We find that at least 25 of the 40 known incomplete combustion products from aviation fuel have lifetimes to reaction with aerosol sulfuric acid of at least months. We estimate that ~109 kg of long-lived products could be deposited per year in the lower stratosphere. We suggest that the high molecular weight organic compounds formed as incomplete combustion products of commercial long-haul aviation could play a significant role in the stratosphere.
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7
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Contributions of Various Sources to the Higher-Concentration Center of CO within the ASM Anticyclone Based on GEOS-Chem Simulations. REMOTE SENSING 2022. [DOI: 10.3390/rs14143322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Satellite observations show that carbon monoxide (CO) concentration centers exist in the tropopause region of the Tibetan Plateau, while their sources and formation mechanism still remain uncertain. In this paper, the 3-D chemical transport model GEOS-Chem is used to conduct sensitivity analysis in 2016. Combined with the analysis data and satellite data, the contribution of three important emission sources (South Asia, East Asia and Southeast Asia) and two important chemical reaction species (CH4 and nonmethane volatile organic compounds (NMVOCs)) to CO in the upper troposphere and lower stratosphere (UTLS) are studied. The results show that in the Asian monsoon region CO emissions originating from the surface are transported to the upper troposphere via a deep convection process and then enter the Asian Summer Monsoon (ASM) anticyclone. The strong ASM anticyclone isolates the mixing process of air inside and outside the anticyclone, upon entry of carbon monoxide-rich air. In the lower stratosphere, the intensity of the ASM anticyclone declines and the air within the anticyclone flows southwestward with monsoon circulation. We found that in the summer Asian monsoon region, South Asia exhibited the highest carbon monoxide concentration transported to the UTLS. CH4 imposed the greatest influence on the CO concentration in the UTLS region. According to the model simulation results, the CO concentrations in the Asian monsoon region at 100 hPa altitudes were higher than those in other regions at the same latitudes. Regarding effects, 43.18% originated from CH4 chemical reactions, 20.81% originated from NMVOC chemical reactions, and 63.33% originated from surface CO emissions, while sinks yielded a negative contribution of −27.32%. Regarding surface CO emissions, East Asia contributed 13.56%, South Asia contributed 39.27%, and Southeast Asia contributed 7.15%.
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8
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Wu D, Shi T, Niu X, Chen Z, Cui J, Chen Y, Zhang X, Liu J, Ji M, Wang X, Pu W. Seasonal to sub-seasonal variations of the Asian Tropopause Aerosols Layer affected by the deep convection, surface pollutants and precipitation. J Environ Sci (China) 2022; 114:53-65. [PMID: 35459514 DOI: 10.1016/j.jes.2021.07.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 07/09/2021] [Indexed: 06/14/2023]
Abstract
The Asian Tropopause Aerosols Layer (ATAL) refers to an accumulation of aerosols in the upper troposphere and lower stratosphere during boreal summer over Asia, which has a fundamental impact on the monsoon system and climate change. In this study, we primarily analyze the seasonal to sub-seasonal variations of the ATAL and the factors potentially influencing those variations based on MERRA2 reanalysis. The ability of the reanalysis to reproduce the ATAL is well validated by CALIPSO observations from May to October 2016. The results reveal that the ATAL has a synchronous spatiotemporal pattern with the development and movement of the Asian Summer Monsoon. Significant enhancement of ATAL intensity is found during the prevailing monsoon period of July-August, with two maxima centered over South Asia and the Arabian Peninsula. Owing to the fluctuations of deep convection, the ATAL shows an episodic variation on a timescale of 7-12 days. Attribution analysis indicates that deep convection dominates the variability of the ATAL with a contribution of 62.7%, followed by a contribution of 36.6% from surface pollutants. The impact of precipitation is limited. The ATAL further shows a clear diurnal variation: the peak of ATAL intensity occurs from 17:30 to 23:30 local time (LT), when the deep convection becomes strongest; the minimum ATAL intensity occurs around 8:30 LT owing to the weakened deep convection and photochemical reactions in clouds. The aerosol components of the ATAL show different spatiotemporal patterns and imply that black carbon and organic carbon come mainly from India, whereas sulfate comes mainly from China during the prevailing monsoon period.
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Affiliation(s)
- Dongyou Wu
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Tenglong Shi
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Xiaoying Niu
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Ziqi Chen
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Jiecan Cui
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yang Chen
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Xueying Zhang
- Jilin Weather Modification Office, Changchun 130000, China
| | - Jun Liu
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Mingxia Ji
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
| | - Xin Wang
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China; School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Wei Pu
- College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China.
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9
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Influence of Indian Summer Monsoon on Tropopause, Trace Gases and Aerosols in Asian Summer Monsoon Anticyclone Observed by COSMIC, MLS and CALIPSO. REMOTE SENSING 2021. [DOI: 10.3390/rs13173486] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The existence of the Asian Summer Monsoon Anticyclone (ASMA) during the summer in the northern hemisphere, upper troposphere and lower stratosphere (UTLS) region plays a significant role in confining the trace gases and aerosols for a long duration, thus affecting regional and global climate. Though several studies have been carried out, our understanding of the trace gases and aerosols variability in the ASMA is limited during different phases of the Indian monsoon. This work quantifies the role of Indian Summer Monsoon (ISM) activity on the tropopause, trace gases (Water Vapor (WV), Ozone (O3), Carbon Monoxide (CO)) and aerosols (Attenuated Scattering Ratio (ASR)) obtained from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC), Microwave Limb Sounder (MLS), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite observations, respectively, during the period 2006–2016. Enhancement in the tropopause altitude, WV, CO, ASR and low tropopause temperatures, O3 in the ASMA region is clearly noticed during peak monsoon months (July and August) with large inter-annual variability. Further, a significant increase in the WV and CO, and decrease in O3 during the active phase of the ISM, strong monsoon years and strong La Niña years in the ASMA is noticed. An enhancement in the ASR values during the strong monsoon years and strong La Niña years is also observed. In addition, our results showed that the presence of deep convection spreading from India land regions to the Bay of Bengal with strong updrafts can transport the trace gases and aerosols to the upper troposphere during active spells, strong monsoon years and La Niña years when compared to their counterparts. Observations show that the ASMA is very sensitive to active spells, strong monsoon years and La Niña years compared to break spells, weak monsoon years and El Niño years. It is concluded that the dynamics play a significant role in constraining several trace gases and aerosols in the ASMA and suggested considering the activity of the summer monsoon while dealing with them at sub-seasonal scales.
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Wang X, Liu K, Zhu L, Li C, Song Z, Li D. Efficient transport of atmospheric microplastics onto the continent via the East Asian summer monsoon. JOURNAL OF HAZARDOUS MATERIALS 2021; 414:125477. [PMID: 33647626 DOI: 10.1016/j.jhazmat.2021.125477] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 02/19/2021] [Accepted: 02/19/2021] [Indexed: 06/12/2023]
Abstract
The presence of microplastics (MPs) in the atmosphere is a global concern because of its environmental and health impacts; however, the monsoonal transport of atmospheric MPs has not yet been investigated. To fully understand the effect of the monsoon on atmospheric MP transport, we conducted a study along the southeast coast of China during the East Asian summer monsoon (EASM). We found that the EASM transports atmospheric MPs back onto the continent at a flux of up to 212.977-213.433 kg/EASM/year. The backward trajectory and wind field results indicate that the EASM provides an effective MP transport pathway from Vietnam, the Philippines, and Malaysia to southeastern China. This suggests that only some of the airborne MPs over the ocean enter the marine ecosystem. The average abundance of atmospheric MPs over the sampling area was 0.39 items/100 m3 (0.39 ± 0.43 items/100 m3) during the EASM season, with high variability among the sampling sites. This study improves our understanding of the impact of the EASM on atmospheric MP transport, which can help quantify the contributions of atmospheric MPs to marine or terrestrial ecosystems.
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Affiliation(s)
- Xiaohui Wang
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
| | - Kai Liu
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
| | - Lixin Zhu
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
| | - Changjun Li
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
| | - Zhangyu Song
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
| | - Daoji Li
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China.
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Bian J, Li D, Bai Z, Li Q, Lyu D, Zhou X. Transport of Asian surface pollutants to the global stratosphere from the Tibetan Plateau region during the Asian summer monsoon. Natl Sci Rev 2020; 7:516-533. [PMID: 34692071 PMCID: PMC8288924 DOI: 10.1093/nsr/nwaa005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 01/16/2020] [Accepted: 01/18/2020] [Indexed: 11/13/2022] Open
Abstract
Due to its surrounding strong and deep Asian summer monsoon (ASM) circulation and active surface pollutant emissions, surface pollutants are transported to the stratosphere from the Tibetan Plateau region, which may have critical impacts on global climate through chemical, microphysical and radiative processes. This article reviews major recent advances in research regarding troposphere-stratosphere transport from the region of the Tibetan Plateau. Since the discovery of the total ozone valley over the Tibetan Plateau in summer from satellite observations in the early 1990s, new satellite-borne instruments have become operational and have provided significant new information on atmospheric composition. In addition, in situ measurements and model simulations are used to investigate deep convection and the ASM anticyclone, surface sources and pathways, atmospheric chemical transformations and the impact on global climate. Also challenges are discussed for further understanding critical questions on microphysics and microchemistry in clouds during the pathway to the global stratosphere over the Tibetan Plateau.
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Affiliation(s)
- Jianchun Bian
- Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dan Li
- Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Zhixuan Bai
- Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Qian Li
- Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Daren Lyu
- Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiuji Zhou
- State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing 100081, China
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Fadnavis S, Sabin TP, Roy C, Rowlinson M, Rap A, Vernier JP, Sioris CE. Elevated aerosol layer over South Asia worsens the Indian droughts. Sci Rep 2019; 9:10268. [PMID: 31311972 PMCID: PMC6635485 DOI: 10.1038/s41598-019-46704-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 07/04/2019] [Indexed: 11/19/2022] Open
Abstract
Droughts have become more severe and recurrent over the Indian sub-continent during the second half of the twentieth century, leading to more severe hydro-climatic and socio-economic impacts over one of the most densely populated parts of the world. So far, droughts have mostly been connected to circulation changes concomitant with the abnormal warming over the Pacific Ocean, prevalently known as "El Niño". Here, exploiting observational data sets and a series of dedicated sensitivity experiments, we show that the severity of droughts during El Niño is amplified (17%) by changes in aerosols. The model experiments simulate the transport of boundary layer aerosols from South Asian countries to higher altitudes (12-18 km) where they form the Asian Tropopause Aerosol Layer (ATAL) (~ 60-120°E, 20-40°N). During El Niño, the anomalous overturning circulation from the East Asian region further enriches the thickness of aerosol layers in the ATAL over the northern part of South Asia. The anomalous aerosol loading in the ATAL reduces insolation over the monsoon region, thereby exacerbating the severity of drought by further weakening the monsoon circulation. Future increases in industrial emissions from both East and South Asia will lead to a wider and thicker elevated aerosol layer in the upper troposphere, potentially amplifying the severity of droughts.
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Affiliation(s)
| | - T P Sabin
- Indian Institute of Tropical Meteorology, Pune, India
| | - Chaitri Roy
- Indian Institute of Tropical Meteorology, Pune, India
| | | | - Alexandru Rap
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - Jean-Paul Vernier
- National Institute of Aerospace, Hampton, Virginia, United States
- NASA Langley Research Center, Hampton, Virginia, United States
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Yu P, Froyd KD, Portmann RW, Toon OB, Freitas SR, Bardeen CG, Brock C, Fan T, Gao R, Katich JM, Kupc A, Liu S, Maloney C, Murphy DM, Rosenlof KH, Schill G, Schwarz JP, Williamson C. Efficient In-Cloud Removal of Aerosols by Deep Convection. GEOPHYSICAL RESEARCH LETTERS 2019; 46:1061-1069. [PMID: 34219825 PMCID: PMC8243348 DOI: 10.1029/2018gl080544] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 12/19/2018] [Accepted: 12/22/2018] [Indexed: 06/11/2023]
Abstract
Convective systems dominate the vertical transport of aerosols and trace gases. The most recent in situ aerosol measurements presented here show that the concentrations of primary aerosols including sea salt and black carbon drop by factors of 10 to 10,000 from the surface to the upper troposphere. In this study we show that the default convective transport scheme in the National Science Foundation/Department of Energy Community Earth System Model results in a high bias of 10-1,000 times the measured aerosol mass for black carbon and sea salt in the middle and upper troposphere. A modified transport scheme, which considers aerosol activation from entrained air above the cloud base and aerosol-cloud interaction associated with convection, dramatically improves model agreement with in situ measurements suggesting that deep convection can efficiently remove primary aerosols. We suggest that models that fail to consider secondary activation may overestimate black carbon's radiative forcing by a factor of 2.
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Affiliation(s)
- Pengfei Yu
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
- Institute for Environment and Climate Research, Jinan UniversityGuangzhouChina
| | - Karl D. Froyd
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Robert W. Portmann
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Owen B. Toon
- Department of Atmospheric and Oceanic SciencesUniversity of Colorado BoulderBoulderCOUSA
- Laboratory for Atmospheric and Space PhysicsUniversity of Colorado BoulderBoulderCOUSA
| | - Saulo R. Freitas
- Goddard Earth Sciences Technology and ResearchUniversities Space Research AssociationColumbiaMDUSA
| | - Charles G. Bardeen
- Atmospheric Chemistry DivisionNational Center for Atmospheric ResearchBoulderCOUSA
| | - Charles Brock
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Tianyi Fan
- College of Global Change and Earth System ScienceBeijing Normal UniversityBeijingChina
| | - Ru‐Shan Gao
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Joseph M. Katich
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Agnieszka Kupc
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
- Now at the Faculty of PhysicsUniversity of ViennaViennaAustria
| | - Shang Liu
- School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefeiChina
| | - Christopher Maloney
- Department of Atmospheric and Oceanic SciencesUniversity of Colorado BoulderBoulderCOUSA
- Laboratory for Atmospheric and Space PhysicsUniversity of Colorado BoulderBoulderCOUSA
| | - Daniel M. Murphy
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Karen H. Rosenlof
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Gregory Schill
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Joshua P. Schwarz
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | - Christina Williamson
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Earth System Research LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
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Zhao P, Zhou X, Chen J, Liu G, Nan S. Global climate effects of summer Tibetan Plateau. Sci Bull (Beijing) 2019; 64:1-3. [PMID: 36659517 DOI: 10.1016/j.scib.2018.11.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Ping Zhao
- State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China; Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China.
| | - Xiuji Zhou
- State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China
| | - Junming Chen
- State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China
| | - Ge Liu
- State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China
| | - Sulan Nan
- State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China
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Madronich S, Björn LO, McKenzie RL. Solar UV radiation and microbial life in the atmosphere. Photochem Photobiol Sci 2018; 17:1918-1931. [PMID: 29978175 DOI: 10.1039/c7pp00407a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Many microorganisms are alive while suspended in the atmosphere, and some seem to be metabolically active during their time there. One of the most important factors threatening their life and activity is solar ultraviolet (UV) radiation. Quantitative understanding of the spatial and temporal survival patterns in the atmosphere, and of the ultimate deposition of microbes to the surface, is limited by a number factors some of which are discussed here. These include consideration of appropriate spectral sensitivity functions for biological damage (e.g. inactivation), and the estimation of UV radiation impingent on a microorganism suspended in the atmosphere. We show that for several bacteria (E. coli, S. typhimurium, and P. acnes) the inactivation rates correlate well with irradiances weighted by the DNA damage spectrum in the UV-B spectral range, but when these organisms show significant UV-A (or visible) sensitivities, the correlations become clearly non-linear. The existence of these correlations enables the use of a single spectrum (here DNA damage) as a proxy for sensitivity spectra of other biological effects, but with some caution when the correlations are strongly non-linear. The radiative quantity relevant to the UV exposure of a suspended particle is the fluence rate at an altitude above ground, while down-welling irradiance at ground-level is the quantity most commonly measured or estimated in satellite-derived climatologies. Using a radiative transfer model that computes both quantities, we developed a simple parameterization to exploit the much larger irradiance data bases to estimate fluence rates, and present the first fluence-rate based climatology of DNA-damaging UV radiation in the atmosphere. The estimation of fluence rates in the presence of clouds remains a particularly challenging problem. Here we note that both reductions and enhancements in the UV radiation field are possible, depending mainly on cloud optical geometry and prevailing solar zenith angles. These complex effects need to be included in model simulations of the atmospheric life cycle of the organisms.
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Lau WKM, Yuan C, Li Z. Origin, Maintenance and Variability of the Asian Tropopause Aerosol Layer (ATAL): The Roles of Monsoon Dynamics. Sci Rep 2018; 8:3960. [PMID: 29500395 PMCID: PMC5834455 DOI: 10.1038/s41598-018-22267-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 02/19/2018] [Indexed: 11/24/2022] Open
Abstract
Using NASA MERRA2 daily data, we investigated the origin, maintenance and variability of the Asian Tropopause Aerosol Layer (ATAL) in relation to variations of the Asia Monsoon Anticyclone (AMA) during the summer of 2008. During May-June, abundant quantities of carbon monoxide (CO), carbonaceous aerosols (CA) and dusts are found in the mid- and upper troposphere over India and China, arising from enhanced biomass burning emissions, as well as westerly transport from the Middle East deserts. During July-August, large quantities of dusts transported from the deserts are trapped and accumulate over the southern and eastern foothills of the Tibetan Plateau. Despite strong precipitation washout, ambient CO, CA and dust are lofted by orographically forced deep convection to great elevations, 12-16 km above sea level, via two key pathways over heavily polluted regions: a) the Himalayas-Gangetic Plain, and b) the Sichuan Basin. Upon entering the upper-troposphere-lower-stratosphere, the pollutants are capped by a stable layer near the tropopause, advected and dispersed by the anticyclonic circulation of AMA, forming the ATAL resembling a planetary-scale "double-stem chimney cloud". The development and variability of the ATAL are strongly linked to the seasonal march and intraseasonal (20-30 days and higher frequency) oscillations of the Asian monsoon.
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Affiliation(s)
- William K M Lau
- Earth System Science Interdisciplinary Center, U. of Maryland, College Park, MD, 20740, USA.
- Department of Atmospheric and Oceanic Sciences, U. of Maryland, College Park, MD, 20740, USA.
| | - Cheng Yuan
- Earth System Science Interdisciplinary Center, U. of Maryland, College Park, MD, 20740, USA
- School of Atmospheric Sciences, Nanjing University, Nanjing, China
| | - Zhanqing Li
- Earth System Science Interdisciplinary Center, U. of Maryland, College Park, MD, 20740, USA
- Department of Atmospheric and Oceanic Sciences, U. of Maryland, College Park, MD, 20740, USA
- State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing, China
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