C. Zhang, á. F. Adames, B. Khouider, B. Wang, D. Yang
Studies of the Madden-Julian Oscillation (MJO) have progressed considerably during the past decades in observations, numerical modeling, and theoretical understanding. Many theoretical attempts have been made to identify the most essential processes responsible for the existence of the MJO. Criteria are proposed to separate a hypothesis from a theory (based on the first principles with quantitative and testable assumptions, able to predict quantitatively the fundamental scales and eastward propagation of the MJO). Four MJO theories are selected to be summarized and compared in this article: the skeleton theory, moisture-mode theory, gravity-wave theory, and trio-interaction theory of the MJO. These four MJO theories are distinct from each other in their key assumptions, parameterized processes, and, particularly, selection mechanisms for the zonal spatial scale, time scale, and eastward propagation of the MJO. The comparison of the four theories and more recent development in MJO dynamical approaches lead to a realization that theoretical thinking of the MJO is diverse and understanding of MJO dynamics needs to be further advanced.
{"title":"Four Theories of the Madden-Julian Oscillation","authors":"C. Zhang, á. F. Adames, B. Khouider, B. Wang, D. Yang","doi":"10.1029/2019RG000685","DOIUrl":"https://doi.org/10.1029/2019RG000685","url":null,"abstract":"<p>Studies of the Madden-Julian Oscillation (MJO) have progressed considerably during the past decades in observations, numerical modeling, and theoretical understanding. Many theoretical attempts have been made to identify the most essential processes responsible for the existence of the MJO. Criteria are proposed to separate a hypothesis from a theory (based on the first principles with quantitative and testable assumptions, able to predict quantitatively the fundamental scales and eastward propagation of the MJO). Four MJO theories are selected to be summarized and compared in this article: the skeleton theory, moisture-mode theory, gravity-wave theory, and trio-interaction theory of the MJO. These four MJO theories are distinct from each other in their key assumptions, parameterized processes, and, particularly, selection mechanisms for the zonal spatial scale, time scale, and eastward propagation of the MJO. The comparison of the four theories and more recent development in MJO dynamical approaches lead to a realization that theoretical thinking of the MJO is diverse and understanding of MJO dynamics needs to be further advanced.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000685","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5906363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin D. Hamlington, Alex S. Gardner, Erik Ivins, Jan T. M. Lenaerts, J. T. Reager, David S. Trossman, Edward D. Zaron, Surendra Adhikari, Anthony Arendt, Andy Aschwanden, Brian D. Beckley, David P. S. Bekaert, Geoffrey Blewitt, Lambert Caron, Don P. Chambers, Hrishikesh A. Chandanpurkar, Knut Christianson, Beata Csatho, Richard I. Cullather, Robert M. DeConto, John T. Fasullo, Thomas Frederikse, Jeffrey T. Freymueller, Daniel M. Gilford, Manuela Girotto, William C. Hammond, Regine Hock, Nicholas Holschuh, Robert E. Kopp, Felix Landerer, Eric Larour, Dimitris Menemenlis, Mark Merrifield, Jerry X. Mitrovica, R. Steven Nerem, Isabel J. Nias, Veronica Nieves, Sophie Nowicki, Kishore Pangaluru, Christopher G. Piecuch, Richard D. Ray, David R. Rounce, Nicole-Jeanne Schlegel, Hélène Seroussi, Manoochehr Shirzaei, William V. Sweet, Isabella Velicogna, Nadya Vinogradova, Thomas Wahl, David N. Wiese, Michael J. Willis
Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea-level observing system, the knowledge of regional sea-level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea-level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea-level change. Here we review the individual processes which lead to sea-level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea-level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea-level observation network—particularly as related to satellite observations—in the improved scientific understanding of the contributors to regional sea-level change.
{"title":"Understanding of Contemporary Regional Sea-Level Change and the Implications for the Future","authors":"Benjamin D. Hamlington, Alex S. Gardner, Erik Ivins, Jan T. M. Lenaerts, J. T. Reager, David S. Trossman, Edward D. Zaron, Surendra Adhikari, Anthony Arendt, Andy Aschwanden, Brian D. Beckley, David P. S. Bekaert, Geoffrey Blewitt, Lambert Caron, Don P. Chambers, Hrishikesh A. Chandanpurkar, Knut Christianson, Beata Csatho, Richard I. Cullather, Robert M. DeConto, John T. Fasullo, Thomas Frederikse, Jeffrey T. Freymueller, Daniel M. Gilford, Manuela Girotto, William C. Hammond, Regine Hock, Nicholas Holschuh, Robert E. Kopp, Felix Landerer, Eric Larour, Dimitris Menemenlis, Mark Merrifield, Jerry X. Mitrovica, R. Steven Nerem, Isabel J. Nias, Veronica Nieves, Sophie Nowicki, Kishore Pangaluru, Christopher G. Piecuch, Richard D. Ray, David R. Rounce, Nicole-Jeanne Schlegel, Hélène Seroussi, Manoochehr Shirzaei, William V. Sweet, Isabella Velicogna, Nadya Vinogradova, Thomas Wahl, David N. Wiese, Michael J. Willis","doi":"10.1029/2019RG000672","DOIUrl":"https://doi.org/10.1029/2019RG000672","url":null,"abstract":"<p>Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea-level observing system, the knowledge of regional sea-level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea-level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea-level change. Here we review the individual processes which lead to sea-level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea-level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea-level observation network—particularly as related to satellite observations—in the improved scientific understanding of the contributors to regional sea-level change.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000672","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5666218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christian L. E. Franzke, Susana Barbosa, Richard Blender, Hege-Beate Fredriksen, Thomas Laepple, Fabrice Lambert, Tine Nilsen, Kristoffer Rypdal, Martin Rypdal, Manuel G, Scotto, Stéphane Vannitsem, Nicholas W. Watkins, Lichao Yang, Naiming Yuan
One of the most intriguing facets of the climate system is that it exhibits variability across all temporal and spatial scales; pronounced examples are temperature and precipitation. The structure of this variability, however, is not arbitrary. Over certain spatial and temporal ranges, it can be described by scaling relationships in the form of power laws in probability density distributions and autocorrelation functions. These scaling relationships can be quantified by scaling exponents which measure how the variability changes across scales and how the intensity changes with frequency of occurrence. Scaling determines the relative magnitudes and persistence of natural climate fluctuations. Here, we review various scaling mechanisms and their relevance for the climate system. We show observational evidence of scaling and discuss the application of scaling properties and methods in trend detection, climate sensitivity analyses, and climate prediction.
{"title":"The Structure of Climate Variability Across Scales","authors":"Christian L. E. Franzke, Susana Barbosa, Richard Blender, Hege-Beate Fredriksen, Thomas Laepple, Fabrice Lambert, Tine Nilsen, Kristoffer Rypdal, Martin Rypdal, Manuel G, Scotto, Stéphane Vannitsem, Nicholas W. Watkins, Lichao Yang, Naiming Yuan","doi":"10.1029/2019RG000657","DOIUrl":"https://doi.org/10.1029/2019RG000657","url":null,"abstract":"<p>One of the most intriguing facets of the climate system is that it exhibits variability across all temporal and spatial scales; pronounced examples are temperature and precipitation. The structure of this variability, however, is not arbitrary. Over certain spatial and temporal ranges, it can be described by scaling relationships in the form of power laws in probability density distributions and autocorrelation functions. These scaling relationships can be quantified by scaling exponents which measure how the variability changes across scales and how the intensity changes with frequency of occurrence. Scaling determines the relative magnitudes and persistence of natural climate fluctuations. Here, we review various scaling mechanisms and their relevance for the climate system. We show observational evidence of scaling and discuss the application of scaling properties and methods in trend detection, climate sensitivity analyses, and climate prediction.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000657","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5716880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. C. Gerstenberger, W. Marzocchi, T. Allen, M. Pagani, J. Adams, L. Danciu, E. H. Field, H. Fujiwara, N. Luco, K.-F. Ma, C. Meletti, M. D. Petersen
Seismic hazard modeling is a multidisciplinary science that aims to forecast earthquake occurrence and its resultant ground shaking. Such models consist of a probabilistic framework that quantifies uncertainty across a complex system; typically, this includes at least two model components developed from Earth science: seismic source and ground motion models. Although there is no scientific prescription for the forecast length, the most common probabilistic seismic hazard analyses consider forecasting windows of 30 to 50 years, which are typically an engineering demand for building code purposes. These types of analyses are the topic of this review paper. Although the core methods and assumptions of seismic hazard modeling have largely remained unchanged for more than 50 years, we review the most recent initiatives, which face the difficult task of meeting both the increasingly sophisticated demands of society and keeping pace with advances in scientific understanding. A need for more accurate and spatially precise hazard forecasting must be balanced with increased quantification of uncertainty and new challenges such as moving from time-independent hazard to forecasts that are time dependent and specific to the time period of interest. Meeting these challenges requires the development of science-driven models, which integrate all information available, the adoption of proper mathematical frameworks to quantify the different types of uncertainties in the hazard model, and the development of a proper testing phase of the model to quantify its consistency and skill. We review the state of the art of the National Seismic Hazard Modeling and how the most innovative approaches try to address future challenges.
{"title":"Probabilistic Seismic Hazard Analysis at Regional and National Scales: State of the Art and Future Challenges","authors":"M. C. Gerstenberger, W. Marzocchi, T. Allen, M. Pagani, J. Adams, L. Danciu, E. H. Field, H. Fujiwara, N. Luco, K.-F. Ma, C. Meletti, M. D. Petersen","doi":"10.1029/2019RG000653","DOIUrl":"https://doi.org/10.1029/2019RG000653","url":null,"abstract":"<p>Seismic hazard modeling is a multidisciplinary science that aims to forecast earthquake occurrence and its resultant ground shaking. Such models consist of a probabilistic framework that quantifies uncertainty across a complex system; typically, this includes at least two model components developed from Earth science: seismic source and ground motion models. Although there is no scientific prescription for the forecast length, the most common probabilistic seismic hazard analyses consider forecasting windows of 30 to 50 years, which are typically an engineering demand for building code purposes. These types of analyses are the topic of this review paper. Although the core methods and assumptions of seismic hazard modeling have largely remained unchanged for more than 50 years, we review the most recent initiatives, which face the difficult task of meeting both the increasingly sophisticated demands of society and keeping pace with advances in scientific understanding. A need for more accurate and spatially precise hazard forecasting must be balanced with increased quantification of uncertainty and new challenges such as moving from time-independent hazard to forecasts that are time dependent and specific to the time period of interest. Meeting these challenges requires the development of science-driven models, which integrate all information available, the adoption of proper mathematical frameworks to quantify the different types of uncertainties in the hazard model, and the development of a proper testing phase of the model to quantify its consistency and skill. We review the state of the art of the National Seismic Hazard Modeling and how the most innovative approaches try to address future challenges.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000653","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5654292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fabio Florindo, Ann Marie Carlton, Paolo D'Odorico, Qingyun Duan, Jasper S. Halekas, Gesine Mollenhauer, Eelco J. Rohling
On behalf of the authors and readers of Reviews of Geophysics (RoG), the American Geophysical Union (AGU), and the broader scientific community, the editors wish to wholeheartedly thank those who reviewed manuscripts for RoG in 2019.
编辑们谨代表《地球物理学评论》(Reviews of Geophysics, RoG)、美国地球物理联合会(American Geophysical Union, AGU)以及更广泛的科学界的作者和读者,衷心感谢2019年《地球物理学评论》的审稿人员。
{"title":"Thank You to Our Peer Reviewers for 2019","authors":"Fabio Florindo, Ann Marie Carlton, Paolo D'Odorico, Qingyun Duan, Jasper S. Halekas, Gesine Mollenhauer, Eelco J. Rohling","doi":"10.1029/2020RG000699","DOIUrl":"https://doi.org/10.1029/2020RG000699","url":null,"abstract":"<p>On behalf of the authors and readers of Reviews of Geophysics (RoG), the American Geophysical Union (AGU), and the broader scientific community, the editors wish to wholeheartedly thank those who reviewed manuscripts for RoG in 2019.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2020RG000699","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6034340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Olivia E. Clifton, Arlene M. Fiore, William J. Massman, Colleen B. Baublitz, Mhairi Coyle, Lisa Emberson, Silvano Fares, Delphine K. Farmer, Pierre Gentine, Giacomo Gerosa, Alex B. Guenther, Detlev Helmig, Danica L. Lombardozzi, J. William Munger, Edward G. Patton, Sally E. Pusede, Donna B. Schwede, Sam J. Silva, Matthias S?rgel, Allison L. Steiner, Amos P. K. Tai
Dry deposition of ozone is an important sink of ozone in near‐surface air. When dry deposition occurs through plant stomata, ozone can injure the plant, altering water and carbon cycling and reducing crop yields. Quantifying both stomatal and nonstomatal uptake accurately is relevant for understanding ozone's impact on human health as an air pollutant and on climate as a potent short‐lived greenhouse gas and primary control on the removal of several reactive greenhouse gases and air pollutants. Robust ozone dry deposition estimates require knowledge of the relative importance of individual deposition pathways, but spatiotemporal variability in nonstomatal deposition is poorly understood. Here we integrate understanding of ozone deposition processes by synthesizing research from fields such as atmospheric chemistry, ecology, and meteorology. We critically review methods for measurements and modeling, highlighting the empiricism that underpins modeling and thus the interpretation of observations. Our unprecedented synthesis of knowledge on deposition pathways, particularly soil and leaf cuticles, reveals process understanding not yet included in widely used models. If coordinated with short‐term field intensives, laboratory studies, and mechanistic modeling, measurements from a few long‐term sites would bridge the molecular to ecosystem scales necessary to establish the relative importance of individual deposition pathways and the extent to which they vary in space and time. Our recommended approaches seek to close knowledge gaps that currently limit quantifying the impact of ozone dry deposition on air quality, ecosystems, and climate.
{"title":"Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling","authors":"Olivia E. Clifton, Arlene M. Fiore, William J. Massman, Colleen B. Baublitz, Mhairi Coyle, Lisa Emberson, Silvano Fares, Delphine K. Farmer, Pierre Gentine, Giacomo Gerosa, Alex B. Guenther, Detlev Helmig, Danica L. Lombardozzi, J. William Munger, Edward G. Patton, Sally E. Pusede, Donna B. Schwede, Sam J. Silva, Matthias S?rgel, Allison L. Steiner, Amos P. K. Tai","doi":"10.1029/2019RG000670","DOIUrl":"https://doi.org/10.1029/2019RG000670","url":null,"abstract":"Dry deposition of ozone is an important sink of ozone in near‐surface air. When dry deposition occurs through plant stomata, ozone can injure the plant, altering water and carbon cycling and reducing crop yields. Quantifying both stomatal and nonstomatal uptake accurately is relevant for understanding ozone's impact on human health as an air pollutant and on climate as a potent short‐lived greenhouse gas and primary control on the removal of several reactive greenhouse gases and air pollutants. Robust ozone dry deposition estimates require knowledge of the relative importance of individual deposition pathways, but spatiotemporal variability in nonstomatal deposition is poorly understood. Here we integrate understanding of ozone deposition processes by synthesizing research from fields such as atmospheric chemistry, ecology, and meteorology. We critically review methods for measurements and modeling, highlighting the empiricism that underpins modeling and thus the interpretation of observations. Our unprecedented synthesis of knowledge on deposition pathways, particularly soil and leaf cuticles, reveals process understanding not yet included in widely used models. If coordinated with short‐term field intensives, laboratory studies, and mechanistic modeling, measurements from a few long‐term sites would bridge the molecular to ecosystem scales necessary to establish the relative importance of individual deposition pathways and the extent to which they vary in space and time. Our recommended approaches seek to close knowledge gaps that currently limit quantifying the impact of ozone dry deposition on air quality, ecosystems, and climate.","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000670","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5679847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lei Li, Jingqiang Tan, Benjamin Schwarz, Franti?ek Staněk, Natalia Poiata, Peidong Shi, Leon Diekmann, Leo Eisner, Dirk Gajewski
Source locations provide fundamental information on earthquakes and lay the foundation for seismic monitoring at all scales. Seismic source location as a classical inverse problem has experienced significant methodological progress during the past century. Unlike the conventional traveltime-based location methods that mainly utilize kinematic information, a new category of waveform-based methods, including partial waveform stacking, time reverse imaging, wavefront tomography, and full waveform inversion, adapted from migration or stacking techniques in exploration seismology has emerged. Waveform-based methods have shown promising results in characterizing weak seismic events at multiple scales, especially for abundant microearthquakes induced by hydraulic fracturing in unconventional and geothermal reservoirs or foreshock and aftershock activity potentially preceding tectonic earthquakes. This review presents a comprehensive summary of the current status of waveform-based location methods, through elaboration of the methodological principles, categorization, and connections, as well as illustration of the applications to natural and induced/triggered seismicity, ranging from laboratory acoustic emission to field hydraulic fracturing-induced seismicity, regional tectonic, and volcanic earthquakes. Taking into account recent developments in instrumentation and the increasing availability of more powerful computational resources, we highlight recent accomplishments and prevailing challenges of different waveform-based location methods and what they promise to offer in the near future.
{"title":"Recent Advances and Challenges of Waveform-Based Seismic Location Methods at Multiple Scales","authors":"Lei Li, Jingqiang Tan, Benjamin Schwarz, Franti?ek Staněk, Natalia Poiata, Peidong Shi, Leon Diekmann, Leo Eisner, Dirk Gajewski","doi":"10.1029/2019RG000667","DOIUrl":"https://doi.org/10.1029/2019RG000667","url":null,"abstract":"<p>Source locations provide fundamental information on earthquakes and lay the foundation for seismic monitoring at all scales. Seismic source location as a classical inverse problem has experienced significant methodological progress during the past century. Unlike the conventional traveltime-based location methods that mainly utilize kinematic information, a new category of waveform-based methods, including partial waveform stacking, time reverse imaging, wavefront tomography, and full waveform inversion, adapted from migration or stacking techniques in exploration seismology has emerged. Waveform-based methods have shown promising results in characterizing weak seismic events at multiple scales, especially for abundant microearthquakes induced by hydraulic fracturing in unconventional and geothermal reservoirs or foreshock and aftershock activity potentially preceding tectonic earthquakes. This review presents a comprehensive summary of the current status of waveform-based location methods, through elaboration of the methodological principles, categorization, and connections, as well as illustration of the applications to natural and induced/triggered seismicity, ranging from laboratory acoustic emission to field hydraulic fracturing-induced seismicity, regional tectonic, and volcanic earthquakes. Taking into account recent developments in instrumentation and the increasing availability of more powerful computational resources, we highlight recent accomplishments and prevailing challenges of different waveform-based location methods and what they promise to offer in the near future.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000667","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5862187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. G. Nisbet, R. E. Fisher, D. Lowry, J. L. France, G. Allen, S. Bakkaloglu, T. J. Broderick, M. Cain, M. Coleman, J. Fernandez, G. Forster, P. T. Griffiths, C. P. Iverach, B. F. J. Kelly, M. R. Manning, P. B. R. Nisbet-Jones, J. A. Pyle, A. Townsend-Small, A. al-Shalaan, N. Warwick, G. Zazzeri
The atmospheric methane burden is increasing rapidly, contrary to pathways compatible with the goals of the 2015 United Nations Framework Convention on Climate Change Paris Agreement. Urgent action is required to bring methane back to a pathway more in line with the Paris goals. Emission reduction from “tractable” (easier to mitigate) anthropogenic sources such as the fossil fuel industries and landfills is being much facilitated by technical advances in the past decade, which have radically improved our ability to locate, identify, quantify, and reduce emissions. Measures to reduce emissions from “intractable” (harder to mitigate) anthropogenic sources such as agriculture and biomass burning have received less attention and are also becoming more feasible, including removal from elevated-methane ambient air near to sources. The wider effort to use microbiological and dietary intervention to reduce emissions from cattle (and humans) is not addressed in detail in this essentially geophysical review. Though they cannot replace the need to reach “net-zero” emissions of CO2, significant reductions in the methane burden will ease the timescales needed to reach required CO2 reduction targets for any particular future temperature limit. There is no single magic bullet, but implementation of a wide array of mitigation and emission reduction strategies could substantially cut the global methane burden, at a cost that is relatively low compared to the parallel and necessary measures to reduce CO2, and thereby reduce the atmospheric methane burden back toward pathways consistent with the goals of the Paris Agreement.
{"title":"Methane Mitigation: Methods to Reduce Emissions, on the Path to the Paris Agreement","authors":"E. G. Nisbet, R. E. Fisher, D. Lowry, J. L. France, G. Allen, S. Bakkaloglu, T. J. Broderick, M. Cain, M. Coleman, J. Fernandez, G. Forster, P. T. Griffiths, C. P. Iverach, B. F. J. Kelly, M. R. Manning, P. B. R. Nisbet-Jones, J. A. Pyle, A. Townsend-Small, A. al-Shalaan, N. Warwick, G. Zazzeri","doi":"10.1029/2019RG000675","DOIUrl":"https://doi.org/10.1029/2019RG000675","url":null,"abstract":"<p>The atmospheric methane burden is increasing rapidly, contrary to pathways compatible with the goals of the 2015 United Nations Framework Convention on Climate Change Paris Agreement. Urgent action is required to bring methane back to a pathway more in line with the Paris goals. Emission reduction from “tractable” (easier to mitigate) anthropogenic sources such as the fossil fuel industries and landfills is being much facilitated by technical advances in the past decade, which have radically improved our ability to locate, identify, quantify, and reduce emissions. Measures to reduce emissions from “intractable” (harder to mitigate) anthropogenic sources such as agriculture and biomass burning have received less attention and are also becoming more feasible, including removal from elevated-methane ambient air near to sources. The wider effort to use microbiological and dietary intervention to reduce emissions from cattle (and humans) is not addressed in detail in this essentially geophysical review. Though they cannot replace the need to reach “net-zero” emissions of CO<sub>2</sub>, significant reductions in the methane burden will ease the timescales needed to reach required CO<sub>2</sub> reduction targets for any particular future temperature limit. There is no single magic bullet, but implementation of a wide array of mitigation and emission reduction strategies could substantially cut the global methane burden, at a cost that is relatively low compared to the parallel and necessary measures to reduce CO<sub>2</sub>, and thereby reduce the atmospheric methane burden back toward pathways consistent with the goals of the Paris Agreement.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000675","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6241168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thomas P?htz, Abram H. Clark, Manousos Valyrakis, Orencio Durán
Predicting the morphodynamics of sedimentary landscapes due to fluvial and aeolian flows requires answering the following questions: Is the flow strong enough to initiate sediment transport, is the flow strong enough to sustain sediment transport once initiated, and how much sediment is transported by the flow in the saturated state (i.e., what is the transport capacity)? In the geomorphological and related literature, the widespread consensus has been that the initiation, cessation, and capacity of fluvial transport, and the initiation of aeolian transport, are controlled by fluid entrainment of bed sediment caused by flow forces overcoming local resisting forces, whereas aeolian transport cessation and capacity are controlled by impact entrainment caused by the impacts of transported particles with the bed. Here the physics of sediment transport initiation, cessation, and capacity is reviewed with emphasis on recent consensus-challenging developments in sediment transport experiments, two-phase flow modeling, and the incorporation of granular physics' concepts. Highlighted are the similarities between dense granular flows and sediment transport, such as a superslow granular motion known as creeping (which occurs for arbitrarily weak driving flows) and system-spanning force networks that resist bed sediment entrainment; the roles of the magnitude and duration of turbulent fluctuation events in fluid entrainment; the traditionally overlooked role of particle-bed impacts in triggering entrainment events in fluvial transport; and the common physical underpinning of transport thresholds across aeolian and fluvial environments. This sheds a new light on the well-known Shields diagram, where measurements of fluid entrainment thresholds could actually correspond to entrainment-independent cessation thresholds.
{"title":"The Physics of Sediment Transport Initiation, Cessation, and Entrainment Across Aeolian and Fluvial Environments","authors":"Thomas P?htz, Abram H. Clark, Manousos Valyrakis, Orencio Durán","doi":"10.1029/2019RG000679","DOIUrl":"https://doi.org/10.1029/2019RG000679","url":null,"abstract":"<p>Predicting the morphodynamics of sedimentary landscapes due to fluvial and aeolian flows requires answering the following questions: Is the flow strong enough to initiate sediment transport, is the flow strong enough to sustain sediment transport once initiated, and how much sediment is transported by the flow in the saturated state (i.e., what is the transport capacity)? In the geomorphological and related literature, the widespread consensus has been that the initiation, cessation, and capacity of fluvial transport, and the initiation of aeolian transport, are controlled by fluid entrainment of bed sediment caused by flow forces overcoming local resisting forces, whereas aeolian transport cessation and capacity are controlled by impact entrainment caused by the impacts of transported particles with the bed. Here the physics of sediment transport initiation, cessation, and capacity is reviewed with emphasis on recent consensus-challenging developments in sediment transport experiments, two-phase flow modeling, and the incorporation of granular physics' concepts. Highlighted are the similarities between dense granular flows and sediment transport, such as a superslow granular motion known as creeping (which occurs for arbitrarily weak driving flows) and system-spanning force networks that resist bed sediment entrainment; the roles of the magnitude and duration of turbulent fluctuation events in fluid entrainment; the traditionally overlooked role of particle-bed impacts in triggering entrainment events in fluvial transport; and the common physical underpinning of transport thresholds across aeolian and fluvial environments. This sheds a new light on the well-known Shields diagram, where measurements of fluid entrainment thresholds could actually correspond to entrainment-independent cessation thresholds.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2020-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2019RG000679","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6088187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ivan D. Haigh, Mark D. Pickering, J. A. Mattias Green, Brian K. Arbic, Arne Arns, S?nke Dangendorf, David F. Hill, Kevin Horsburgh, Tom Howard, Déborah Idier, David A. Jay, Leon J?nicke, Serena B. Lee, Malte Müller, Michael Schindelegger, Stefan A. Talke, Sophie-Berenice Wilmes, Philip L. Woodworth
Scientists and engineers have observed for some time that tidal amplitudes at many locations are shifting considerably due to nonastronomical factors. Here we review comprehensively these important changes in tidal properties, many of which remain poorly understood. Over long geological time scales, tectonic processes drive variations in basin size, depth, and shape and hence the resonant properties of ocean basins. On shorter geological time scales, changes in oceanic tidal properties are dominated by variations in water depth. A growing number of studies have identified widespread, sometimes regionally coherent, positive, and negative trends in tidal constituents and levels during the 19th, 20th, and early 21st centuries. Determining the causes is challenging because a tide measured at a coastal gauge integrates the effects of local, regional, and oceanic changes. Here, we highlight six main factors that can cause changes in measured tidal statistics on local scales and a further eight possible regional/global driving mechanisms. Since only a few studies have combined observations and models, or modeled at a temporal/spatial resolution capable of resolving both ultralocal and large-scale global changes, the individual contributions from local and regional mechanisms remain uncertain. Nonetheless, modeling studies project that sea level rise and climate change will continue to alter tides over the next several centuries, with regionally coherent modes of change caused by alterations to coastal morphology and ice sheet extent. Hence, a better understanding of the causes and consequences of tidal variations is needed to help assess the implications for coastal defense, risk assessment, and ecological change.
{"title":"The Tides They Are A-Changin': A Comprehensive Review of Past and Future Nonastronomical Changes in Tides, Their Driving Mechanisms, and Future Implications","authors":"Ivan D. Haigh, Mark D. Pickering, J. A. Mattias Green, Brian K. Arbic, Arne Arns, S?nke Dangendorf, David F. Hill, Kevin Horsburgh, Tom Howard, Déborah Idier, David A. Jay, Leon J?nicke, Serena B. Lee, Malte Müller, Michael Schindelegger, Stefan A. Talke, Sophie-Berenice Wilmes, Philip L. Woodworth","doi":"10.1029/2018RG000636","DOIUrl":"https://doi.org/10.1029/2018RG000636","url":null,"abstract":"<p>Scientists and engineers have observed for some time that tidal amplitudes at many locations are shifting considerably due to nonastronomical factors. Here we review comprehensively these important changes in tidal properties, many of which remain poorly understood. Over long geological time scales, tectonic processes drive variations in basin size, depth, and shape and hence the resonant properties of ocean basins. On shorter geological time scales, changes in oceanic tidal properties are dominated by variations in water depth. A growing number of studies have identified widespread, sometimes regionally coherent, positive, and negative trends in tidal constituents and levels during the 19th, 20th, and early 21st centuries. Determining the causes is challenging because a tide measured at a coastal gauge integrates the effects of local, regional, and oceanic changes. Here, we highlight six main factors that can cause changes in measured tidal statistics on local scales and a further eight possible regional/global driving mechanisms. Since only a few studies have combined observations and models, or modeled at a temporal/spatial resolution capable of resolving both ultralocal and large-scale global changes, the individual contributions from local and regional mechanisms remain uncertain. Nonetheless, modeling studies project that sea level rise and climate change will continue to alter tides over the next several centuries, with regionally coherent modes of change caused by alterations to coastal morphology and ice sheet extent. Hence, a better understanding of the causes and consequences of tidal variations is needed to help assess the implications for coastal defense, risk assessment, and ecological change.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":null,"pages":null},"PeriodicalIF":25.2,"publicationDate":"2019-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1029/2018RG000636","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6219828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}