A Synthesis of Observations of Aerosol-cloud Interactions Over the Pristine, Biologically Active Southern Ocean and the Implications for Global Climate Model Predictions PDF Download
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Author: Isabel Louise McCoy
Publisher:
ISBN:
Category :
Languages : en
Pages : 121
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Book Description
The change in planetary albedo due to aerosol-cloud interactions (aci) during the industrial era is the leading source of uncertainty in inferring Earth's climate sensitivity to increased greenhouse gases from the historical record. Examining pristine environments such as the Southern Ocean (SO) helps us to understand the pre-industrial (PI) state and constrain radiative forcing associated with aci (RFaci). Cloud droplet number concentration (Nd) is a key aci indicator variable. Using global climate models (GCMs), this study finds that the hemispheric contrast in Nd of liquid clouds between the pristine SO and the polluted Northern Hemisphere observed in the present-day (PD) can be used as a proxy for the increase in Nd from the PI. The hemispheric difference constraint and MODIS satellite observations suggest that PI Nd may have been higher than previously thought and provide an estimate of RFaci between -1.2 and -0.6 Wm-2. Southern Ocean liquid clouds can reach Nd levels comparable to the polluted outflows of East Asia and the United States despite persistent precipitation depletion associated with mid-latitude storm systems. This high Nd in one of the most pristine regions on Earth motivates further investigation of the mechanisms driving Nd in the real world and better inclusion of the mechanisms in models. In this study, aerosol and cloud microphysical data from the 2018 Southern Ocean Cloud Radiation Aerosol Transport Experimental Study (SOCRATES) aircraft campaign are used to identify a novel and potentially important mechanism missing or poorly represented in models: production of new particles through synoptic uplift. The small, Aitken mode particles produced in this process dominate the free tropospheric atmosphere in the summertime SO. We find it is likely that entrainment of free tropospheric Aitken aerosols is a leading contributor to sub-cloud cloud condensation nuclei and thus may be a key control on Nd. The free tropospheric Aitken reservoir may maintain the persistently high Nd observed across the SO against precipitation depletion. Finally, our observational comparisons with nudged Community Atmosphere Model (CAM6) hindcasts highlight large aerosol number and composition discrepancies that may significantly and negatively impact the ability of current climate models to capture aci in pristine, PI environments.
Author: Isabel Louise McCoy
Publisher:
ISBN:
Category :
Languages : en
Pages : 121
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Book Description
The change in planetary albedo due to aerosol-cloud interactions (aci) during the industrial era is the leading source of uncertainty in inferring Earth's climate sensitivity to increased greenhouse gases from the historical record. Examining pristine environments such as the Southern Ocean (SO) helps us to understand the pre-industrial (PI) state and constrain radiative forcing associated with aci (RFaci). Cloud droplet number concentration (Nd) is a key aci indicator variable. Using global climate models (GCMs), this study finds that the hemispheric contrast in Nd of liquid clouds between the pristine SO and the polluted Northern Hemisphere observed in the present-day (PD) can be used as a proxy for the increase in Nd from the PI. The hemispheric difference constraint and MODIS satellite observations suggest that PI Nd may have been higher than previously thought and provide an estimate of RFaci between -1.2 and -0.6 Wm-2. Southern Ocean liquid clouds can reach Nd levels comparable to the polluted outflows of East Asia and the United States despite persistent precipitation depletion associated with mid-latitude storm systems. This high Nd in one of the most pristine regions on Earth motivates further investigation of the mechanisms driving Nd in the real world and better inclusion of the mechanisms in models. In this study, aerosol and cloud microphysical data from the 2018 Southern Ocean Cloud Radiation Aerosol Transport Experimental Study (SOCRATES) aircraft campaign are used to identify a novel and potentially important mechanism missing or poorly represented in models: production of new particles through synoptic uplift. The small, Aitken mode particles produced in this process dominate the free tropospheric atmosphere in the summertime SO. We find it is likely that entrainment of free tropospheric Aitken aerosols is a leading contributor to sub-cloud cloud condensation nuclei and thus may be a key control on Nd. The free tropospheric Aitken reservoir may maintain the persistently high Nd observed across the SO against precipitation depletion. Finally, our observational comparisons with nudged Community Atmosphere Model (CAM6) hindcasts highlight large aerosol number and composition discrepancies that may significantly and negatively impact the ability of current climate models to capture aci in pristine, PI environments.
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309466806
Category : Science
Languages : en
Pages : 151
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Book Description
The ocean is an integral component of the Earth's climate system. It covers about 70% of the Earth's surface and acts as its primary reservoir of heat and carbon, absorbing over 90% of the surplus heat and about 30% of the carbon dioxide associated with human activities, and receiving close to 100% of fresh water lost from land ice. With the accumulation of greenhouse gases in the atmosphere, notably carbon dioxide from fossil fuel combustion, the Earth's climate is now changing more rapidly than at any time since the advent of human societies. Society will increasingly face complex decisions about how to mitigate the adverse impacts of climate change such as droughts, sea-level rise, ocean acidification, species loss, changes to growing seasons, and stronger and possibly more frequent storms. Observations play a foundational role in documenting the state and variability of components of the climate system and facilitating climate prediction and scenario development. Regular and consistent collection of ocean observations over decades to centuries would monitor the Earth's main reservoirs of heat, carbon dioxide, and water and provides a critical record of long-term change and variability over multiple time scales. Sustained high-quality observations are also needed to test and improve climate models, which provide insights into the future climate system. Sustaining Ocean Observations to Understand Future Changes in Earth's Climate considers processes for identifying priority ocean observations that will improve understanding of the Earth's climate processes, and the challenges associated with sustaining these observations over long timeframes.
Author: Carlos R. Mechoso
Publisher: Cambridge University Press
ISBN: 1108650872
Category : Science
Languages : en
Pages : 359
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Book Description
Climate variability in different ocean basins can impact one another, for instance the El Niño/Southern Oscillation (ENSO) in the Pacific Ocean has remote effects on other tropical oceans around the world, which in turn modulate ENSO. With chapters by eminent researchers, this book provides a comprehensive review on how interactions among the climates in different ocean basins are key contributors to global climate variability. It discusses how interbasin interactions are mediated by oceanic and atmospheric bridges and explains exciting new possibilities for enhancing climate prediction globally. The first part of the book covers essential theory and introduces the basic mechanisms for remote connection and local amplification. The second presents outstanding examples. The latter part discusses applications to cases of societal interest such as impacts on monsoon systems and expectations after climate change. This comprehensive reference is a useful resource for graduate students and researchers in the atmospheric and ocean sciences.
Author: Chuyan Tan
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 0
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Book Description
Shifts in Southern Ocean (SO, 40 − 85oS) shortwave cloud feedback (SWF B) towards more positive values are the dominant contributor to higher effective climate sensitivity (ECS) in Coupled Model Intercomparison Project phase 6 (CMIP6) models. The positive shift in SW[subscript]F B from CMIP5 to CMIP6 global climate model (GCMs) can be traced back to the greater reduction in low cloud cover and the weaker cloud liquid water response to warming in the SO. To provide an observational constraint on the GCM SO SW[subscript]F B, we use a simplified physical model to connect the SO SW[subscript]F B to the change in column-integrated liquid water mass (LWP) and the susceptibility of albedo to LWP in 50 CMIP5/6 GCMs. In turn, we predict the responses of LWP to warming using a cloud-controlling factor (CCF) model. The combination of CCF model and radiative susceptibility explains about 50% of the variance in the GCM-simulated SW[subscript]F B in the SO. Observations of SW radiative fluxes, LWP, and CCFs are used to constrain the SO SW[subscript]F B. This yields a constrained response of SO LWP to warming of 2.76 − 4.19 g m−2K−1, relative to the total GCM range of 0.64 − 9.33 g m−2K−1. The susceptibility of albedo to LWP is constrained to be 0.42 − 0.85 (kg m−2)−1 , relative to the GCM range of 0.30 − 3.91 (kg m−2)−1 , where albedo is unitless. The constraint on the contribution of SO SW[subscript]F B to global cloud feedback is −0.17 − 0.04 Wm−2K−1, relative to GCM range of −0.28 − 0.27 Wm−2K−1. In summary, observations suggest a moderate negative to weak positive SO SW[subscript]F B.
Author: Panel on Aerosol Radiative Forcing and Climate Change
Publisher: National Academies Press
ISBN: 0309588871
Category : Science
Languages : en
Pages : 180
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Book Description
This book recommends the initiation of an "integrated" research program to study the role of aerosols in the predicted global climate change. Current understanding suggest that, even now, aerosols, primarily from anthropogenic sources, may be reducing the rate of warming caused by greenhouse gas emissions. In addition to specific research recommendations, this book forcefully argues for two kinds of research program integration: integration of the individual laboratory, field, and theoretical research activities and an integrated management structure that involves all of the concerned federal agencies.
Author: Srishti Dasarathy
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Tropospheric marine aerosol presence in the western Antarctic is coupled to physical and biological processes. These aerosols may be biogenic, formed from the activity of primary producers, and can be associated with seasonal dynamics of sea ice melt and phytoplankton blooms. These aerosols may also influence local environments of polar regions by absorbing and scattering solar radiation and by initiating cloud formation. To study tropospheric marine aerosol in the remote marine Bellingshausen Sea environment, we used a specialized instrument onboard the NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) capable of detecting the presence of aerosols at altitudes close to the sea surface. We termed this measurement marine aerosol optical depth (MAOD). To further support these observations, we also examined coarse-mode aerosol optical depth (AODC), often used as a proxy for sea spray aerosol (SSA). We used MAOD and AODC to examine trends in marine tropospheric aerosol and undertook a multi-year remote sensing analysis in the Bellingshausen Sea from 2006-2018. Across open ocean to coastal regions, daily fluctuations in nighttime and daytime winds, respectively, drove increasing MAOD and AODC. MAOD depicted strong correlations with wind speed across the open ocean and weak correlations in coastal regions, suggesting that daily fluxes in wind speed drive the production of SSA. In the open ocean, we further observed that warmer SST enhanced AODC and the associated production of SSA, supporting prior studies. We also observed seasonal increases in MAOD alongside a seasonal increase in chl-a and the melt of sea ice; these patterns suggest that biological activity of primary producers likely contributed towards magnitudes of marine tropospheric aerosol. This work is also the first to distinguish a late winter to early spring temporal MAOD signal, likely tied to an aerosol source from either venting of biogenic aerosol from breaks in sea ice or to the production of SSA resulting from pulses in wind speed. Our work extends upon previous findings of marine aerosol in polar environments and more fully characterizes interactions during polar winter.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309314852
Category : Science
Languages : en
Pages : 276
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Book Description
The growing problem of changing environmental conditions caused by climate destabilization is well recognized as one of the defining issues of our time. The root problem is greenhouse gas emissions, and the fundamental solution is curbing those emissions. Climate geoengineering has often been considered to be a "last-ditch" response to climate change, to be used only if climate change damage should produce extreme hardship. Although the likelihood of eventually needing to resort to these efforts grows with every year of inaction on emissions control, there is a lack of information on these ways of potentially intervening in the climate system. As one of a two-book report, this volume of Climate Intervention discusses albedo modification - changing the fraction of incoming solar radiation that reaches the surface. This approach would deliberately modify the energy budget of Earth to produce a cooling designed to compensate for some of the effects of warming associated with greenhouse gas increases. The prospect of large-scale albedo modification raises political and governance issues at national and global levels, as well as ethical concerns. Climate Intervention: Reflecting Sunlight to Cool Earth discusses some of the social, political, and legal issues surrounding these proposed techniques. It is far easier to modify Earth's albedo than to determine whether it should be done or what the consequences might be of such an action. One serious concern is that such an action could be unilaterally undertaken by a small nation or smaller entity for its own benefit without international sanction and regardless of international consequences. Transparency in discussing this subject is critical. In the spirit of that transparency, Climate Intervention: Reflecting Sunlight to Cool Earth was based on peer-reviewed literature and the judgments of the authoring committee; no new research was done as part of this study and all data and information used are from entirely open sources. By helping to bring light to this topic area, this book will help leaders to be far more knowledgeable about the consequences of albedo modification approaches before they face a decision whether or not to use them.
Author: Constantin Andronache
Publisher: Elsevier
ISBN: 012810550X
Category : Science
Languages : en
Pages : 302
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Book Description
Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. - Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate - Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry - Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
Author: Victoriya P. Yurchnik
Publisher: Cambridge Scholars Publishing
ISBN: 1443830887
Category : Science
Languages : en
Pages : 115
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Book Description
Atmosphere Aerosol, Phytoplankton and its Influence on Climate Forming in the Pacific Ocean: Measurement New Methods is a collection of new articles by young academics, students and PhD students who participated in the 1st International Sailing Conference of Climate Forcing, held on the board the Sailing Training Ship Nadezhda in the Sea of Japan and the Okhtosk Sea in August 2010. The collection presents a vivid overview of current problems in the research fields of atmosphere aerosol, phytoplankton communities, volcanic activities and hydroacoastics in order to investigate climate change’s influence on phytoplankton communities. This collection of articles will be of interest to researchers and specialists in the fields of atmosphere and ocean monitoring, and climate forcing.
Author: Christopher Charles Chapman
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The Southern Ocean, which lies south of approximately 35 degrees S and completely encircles the Antarctic continent, is considered to be a unique and important component of the Earth's climate system. The Southern Ocean is home to the world's strongest current system, the Antarctic Circumpolar Current (ACC), which connects the Earth's major ocean basins, mediates the southward transfer of heat, and strongly influences climate on both short and millennial time scales. However, due primarily to lack of observations and insufficient computing power, the dynamics of the Antarctic Circumpolar Current are poorly understood. Modern ocean observing technology and advanced numerical modelling have revealed that the ACC is composed of numerous fine-scale features: strong, narrow currents called "jets" and ring shaped, turbulent features known as "eddies". Although it is widely acknowledged that the nature of the Southern Ocean's flow field has a dramatic influence on the dynamics of the ACC and its interaction with the global climate system, exactly how and why are still questions that perplex oceanographers. The work conducted in this thesis investigates how the fine scale nature of the Southern Ocean flow affects the system as a whole. A particular focus is the interaction of these small scale features with bathymetry. Using a combination of in-situ observations, data collected from satellites and the output of high-resolution numerical models, a newly discovered mode of low-frequency variability, dubbed ̀̀jet--jumping", whereby two jets that pass close to each other near a particular topographic feature show strongly anti-correlated behaviour: one jet strengthening while the other weakens. A dynamical explanation of this behaviour is proposed: variability in the jets arises due to their interaction with a vortex generated through eddy-topography interaction. The predictions of this framework are tested in an idealised numerical model of the Southern Ocean as well as several case studies conducted using sea-surface height altimetry. By adapting methods from signal processing, improvements to an existing method for the detection of jets in the Southern Ocean are proposed. This new method is compared with several existing methods for jet detection, both quantitatively and qualitatively. The new method is found to have superior error performance when compared to with several existing methods. Qualitative comparisons are undertaken using output from an eddy-resolving numerical simulation. It is found that in a global sense, all methods compared are in broad agreement in the placement of jets. However, it is shown that the nature of detected jet field differs depending on the method used. In particular, the new method reveals a finer-scale, more complex jet field than popular contour methods. Finally, the dynamics of s̀̀torm tracks", regions of anomalously high eddy kinetic energy, are explored using a primitive equation model with idealised bottom topography. Using the output of this model, a dynamical mechanism for the formation and downstream development of storm tracks is developed. In this mechanism, it is large scale, topographically forced stationary meanders that initiate the storm track, while eddy-eddy interactions cause the storm track to develop downstream.
