Extratropical shortwave cloud feedbacks in the context of the global circulation and hydrological cycle

Abstract Variability in the strength of low-cloud feedbacks across climate models is the primary contributor to the spread in their estimates of equilibrium climate sensitivity (ECS). This raises the question: What are the regional implications for key features of tropical climate of globally weak versus strong low-cloud feedbacks in response to greenhouse gas–induced warming? To address this question and formalize our understanding of cloud controls on tropical climate, we perform a suite of idealized fully coupled and slab-ocean climate simulations across which we systematically scale the strength of the low-cloud-cover feedback under abrupt 2 × CO2 forcing within a single model, thereby isolating the impact of low-cloud feedback strength. The feedback strength is varied by modifying the stratus cloud fraction so that it is a function of not only local conditions but also global temperature in a series of abrupt 2 × CO2 sensitivity experiments. The unperturbed decrease in low cloud cover (LCC) under 2 × CO2 is greatest in the mid- and high-latitude oceans, and the subtropical eastern Pacific and Atlantic, a pattern that is magnified as the feedback strength is scaled. Consequently, sea surface temperature (SST) increases more in these regions as well as the Pacific cold tongue. As the strength of the low-cloud feedback increases this results in not only increased ECS, but also an enhanced reduction of the large-scale zonal and meridional SST gradients (structural climate sensitivity), with implications for the atmospheric Hadley and Walker circulations, as well as the hydrological cycle. The relevance of our results to simulating past warm climate is also discussed.

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Planktonic foraminiferal spine versus shell carbonate Na incorporation in relation to salinity

10.5194/bg-2018-454 ◽

2018 ◽

Cited By ~ 1

Author(s):

Eveline M. Mezger ◽

Lennart J. de Nooijer ◽

Jacqueline Bertlich ◽

Jelle Bijma ◽

Dirk Nürnberg ◽

...

Keyword(s):

Hydrological Cycle ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Culture Studies ◽

Global Circulation ◽

Relative Contribution ◽

Icp Ms ◽

Shell Chemistry ◽

Shell Carbonate ◽

Micro Analysis

Abstract. Sea surface salinity is one of the most important parameters to reconstruct in paleoclimatology, reflecting amongst others the hydrological cycle, paleo-density, ice volume, and regional and global circulation of water masses. Recent culture studies and a Red Sea field study revealed a significant positive relation between salinity and Na incorporation within benthic and planktonic foraminiferal shells. However, these studies reported varying partitioning of Na between and within the same species. The latter could be associated with ontogenetic variations, most likely spine loss. Varying Na concentrations were observed in different parts of foraminiferal shells, with especially spines and regions close to the primary organic sheet being enriched in Na. In this study, we unravel the Na composition of different components of the planktonic foraminiferal shell wall using Electron Probe Micro Analysis (EPMA) and solution-ICP-MS. A model is presented to interpret EPMA data for spines and spine bases to quantitatively assess differences in composition and contribution to whole shell Na/Ca signals. The same model can also be applied to other spatial inhomogeneities observed in foraminiferal shell chemistry, like elemental (e.g. Mg, Na, S) banding and/or hotspots. The relative contribution of shell calcite, organic linings, spines and spine bases to whole shell Na chemistry is considered quantitatively. This study shows that whereas the high Na areas may be susceptible to taphonomy, the Na chemistry of the shell itself seems relatively robust. Comparing both shell and spine Na/Ca values with salinity shows that shell chemistry records salinity, albeit with a very modest slope.

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Planktonic foraminiferal spine versus shell carbonate Na incorporation in relation to salinity

Biogeosciences ◽

10.5194/bg-16-1147-2019 ◽

2019 ◽

Vol 16 (6) ◽

pp. 1147-1165 ◽

Cited By ~ 3

Author(s):

Eveline M. Mezger ◽

Lennart J. de Nooijer ◽

Jacqueline Bertlich ◽

Jelle Bijma ◽

Dirk Nürnberg ◽

...

Keyword(s):

Hydrological Cycle ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Culture Studies ◽

Global Circulation ◽

Relative Contribution ◽

Icp Ms ◽

Shell Chemistry ◽

Shell Carbonate ◽

Micro Analysis

Abstract. Sea surface salinity is one of the most important parameters to reconstruct in paleoclimatology, reflecting amongst other things the hydrological cycle, paleodensity, ice volume, and regional and global circulation of water masses. Recent culture studies and a Red Sea field study revealed a significant positive relation between salinity and Na incorporation within benthic and planktonic foraminiferal shells. However, these studies reported varying partitioning of Na between and within the same species. The latter could be associated with ontogenetic variations, most likely spine loss. Varying Na concentrations were observed in different parts of foraminiferal shells, with spines and regions close to the primary organic sheet being especially enriched in Na. In this study, we unravel the Na composition of different components of the planktonic foraminiferal shell wall using electron probe micro-analysis (EPMA) and solution ICP-MS. A model is presented to interpret EPMA data for spines and spine bases to quantitatively assess differences in composition and contribution to whole-shell Na∕Ca signals. The same model can also be applied to other spatial inhomogeneities observed in foraminiferal shell chemistry, like elemental (e.g., Mg, Na, S) banding and/or hotspots. The relative contribution of shell carbonate, organic linings, spines and spine bases to whole-shell Na chemistry is considered quantitatively. This study shows that whereas the high Na areas may be susceptible to taphonomic alterations, the Na chemistry of the shell itself seems relatively robust. Comparing both shell and spine Na∕Ca values with salinity shows that shell chemistry records salinity, albeit with a very modest slope.

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Cloud Feedbacks in the Climate System: A Critical Review

Journal of Climate ◽

10.1175/jcli-3243.1 ◽

2005 ◽

Vol 18 (2) ◽

pp. 237-273 ◽

Cited By ~ 660

Author(s):

Graeme L. Stephens

Keyword(s):

Critical Review ◽

Hydrological Cycle ◽

Cloud Feedback ◽

Climate System ◽

Climate Forcing ◽

Alternative Methods ◽

Radiation Budget ◽

Climate Feedback ◽

Theoretical Argument ◽

Cloud Feedbacks

Abstract This paper offers a critical review of the topic of cloud–climate feedbacks and exposes some of the underlying reasons for the inherent lack of understanding of these feedbacks and why progress might be expected on this important climate problem in the coming decade. Although many processes and related parameters come under the influence of clouds, it is argued that atmospheric processes fundamentally govern the cloud feedbacks via the relationship between the atmospheric circulations, cloudiness, and the radiative and latent heating of the atmosphere. It is also shown how perturbations to the atmospheric radiation budget that are induced by cloud changes in response to climate forcing dictate the eventual response of the global-mean hydrological cycle of the climate model to climate forcing. This suggests that cloud feedbacks are likely to control the bulk precipitation efficiency and associated responses of the planet’s hydrological cycle to climate radiative forcings. The paper provides a brief overview of the effects of clouds on the radiation budget of the earth–atmosphere system and a review of cloud feedbacks as they have been defined in simple systems, one being a system in radiative–convective equilibrium (RCE) and others relating to simple feedback ideas that regulate tropical SSTs. The systems perspective is reviewed as it has served as the basis for most feedback analyses. What emerges is the importance of being clear about the definition of the system. It is shown how different assumptions about the system produce very different conclusions about the magnitude and sign of feedbacks. Much more diligence is called for in terms of defining the system and justifying assumptions. In principle, there is also neither any theoretical basis to justify the system that defines feedbacks in terms of global–time-mean changes in surface temperature nor is there any compelling empirical evidence to do so. The lack of maturity of feedback analysis methods also suggests that progress in understanding climate feedback will require development of alternative methods of analysis. It has been argued that, in view of the complex nature of the climate system, and the cumbersome problems encountered in diagnosing feedbacks, understanding cloud feedback will be gleaned neither from observations nor proved from simple theoretical argument alone. The blueprint for progress must follow a more arduous path that requires a carefully orchestrated and systematic combination of model and observations. Models provide the tool for diagnosing processes and quantifying feedbacks while observations provide the essential test of the model’s credibility in representing these processes. While GCM climate and NWP models represent the most complete description of all the interactions between the processes that presumably establish the main cloud feedbacks, the weak link in the use of these models lies in the cloud parameterization imbedded in them. Aspects of these parameterizations remain worrisome, containing levels of empiricism and assumptions that are hard to evaluate with current global observations. Clearly observationally based methods for evaluating cloud parameterizations are an important element in the road map to progress. Although progress in understanding the cloud feedback problem has been slow and confused by past analysis, there are legitimate reasons outlined in the paper that give hope for real progress in the future.

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"Linguistic heritage": From rags to riches, a Cinderella story of an idea in (limited) global circulation

PsycEXTRA Dataset ◽

10.1037/e678192011-001 ◽

2010 ◽

Author(s):

Fenigsen Janina

Keyword(s):

Global Circulation

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STUDY OF POND STATUS IN INDIA : A REVIEW

FLORA AND FAUNA ◽

10.33451/florafauna.v23i1pp99-104 ◽

2017 ◽

Vol 23 (1) ◽

Author(s):

V.K. YADAV ◽

SONAM SHARMA ◽

A.K. SRIVASTAVA ◽

P.K. KHARE

Keyword(s):

Fresh Water ◽

Land Surface ◽

Human Population ◽

Climate Changes ◽

Hydrological Cycle ◽

Habitat Destruction ◽

Conservation Strategy ◽

Goods And Services ◽

Human Use ◽

Over Exploitation

Ponds are an important fresh water critical ecosystem for plants and animals providing goods and services including food, fodder, fish, irrigation, hydrological cycle, shelter, medicine, culture, aesthetic and recreation. Ponds cover less than 2 percent of worlds land surface. Ponds are important source of fresh water for human use. These are threatened by urbanization, industrialization, over exploitation, fragmentation, habitat destruction, pollution, illegal capturing of land and climate changes. These above factors have been destroying ponds very rapidly putting them in danger of extinction of a great number of local biodiversity. It is necessary to formulate a correct conservation strategy for pond restoration in order to meet the growing needs of fresh water by increasing the human population. Some measures have been compiled and proposed in the present review.

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