Mapping manifestations of parametric uncertainty in projected pelagic oxygen concentrations back to contemporary local model fidelity

AbstractPelagic biogeochemical models (BGCMs) have matured into generic components of Earth System Models. BGCMs mimic the effects of marine biota on oceanic nutrient, carbon and oxygen cycles. They rely on parameters that are adjusted to match observed conditions. Such parameters are key to determining the models’ responses to changing environmental conditions. However, many of these parameters are difficult to constrain and constitute a major source of uncertainty in BGCM projections. Here we use, for the first time, variance-based sensitivity analyses to map BGCM parameter uncertainties onto their respective local manifestation in model entities (such as oceanic oxygen concentrations) for both contemporary climate and climate projections. The mapping effectively relates local uncertainties of projections to the uncertainty of specific parameters. Further, it identifies contemporary benchmarking regions, where the uncertainties of specific parameters manifest themselves, thereby facilitating an effective parameter refinement and a reduction of the associated uncertainty. Our results demonstrate that the parameters that are linked to uncertainties in projections may differ from those parameters that facilitate model conformity with present-day observations. In summary, we present a practical approach to the general question of where present-day model fidelity may be indicative for reliable projections.

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Die Kastanie im Engadin – oder was halten Baumarten von modellierten Potenzialgebieten? Chestnut in the Engadine – what do tree species think about model predictions?

Schweizerische Zeitschrift fur Forstwesen ◽

10.3188/szf.2008.0326 ◽

2008 ◽

Vol 159 (10) ◽

pp. 326-335 ◽

Cited By ~ 6

Author(s):

Niklaus E. Zimmermann ◽

Harald Bugmann

Keyword(s):

Tree Species ◽

Expert Knowledge ◽

Forest Succession ◽

Future Climate ◽

Sensitivity Analyses ◽

Climate Projections ◽

Distribution Models ◽

Modeling Approaches ◽

Model Predictions ◽

National Analysis

New IPCC climate projections suggest drastic changes in future climate. We discuss two commonly used modeling approaches, statistical distribution models and dynamic forest succession models, as they are suitable for assessing expected effects of climate change on the tree species distribution in Switzerland and for assisting management decisions in forestry. We discuss the basic assumptions and the strengths and weaknesses of the two approaches, without an understanding of which it is impossible to fully judge the outcome of modeling exercises. We give an overview of results from applying these two modeling approaches in Switzerland and in the Alps and discuss their appropriate use. We believe that these models are an important basis for decision making in the face of highly uncertain development of future climate. Nonetheless, models do not represent an exact copy of reality. Plausibility analyses are necessary in order to assess the results' usefulness and precision. Sensitivity analyses and a critical comparison of model results with expert knowledge of current forests, long measurement time series and other data are important. Also, dialog with practitioners and managers is not only important for checking the plausibility of model predictions under current conditions, but may also serve to improve the evaluation of future projections. We propose to apply models to the whole of Switzerland and to many tree species. Such a concerted national analysis may serve the adaptive management of forests and may strengthen dialog between researchers and practitioners.

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Decadal trends in the ocean carbon sink

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1900371116 ◽

2019 ◽

pp. 201900371 ◽

Cited By ~ 8

Author(s):

Tim DeVries ◽

Corinne Le Quéré ◽

Oliver Andrews ◽

Sarah Berthet ◽

Judith Hauck ◽

...

Keyword(s):

Climate Variability ◽

Decadal Variability ◽

Carbon Sink ◽

Carbon Accumulation ◽

Climate Projections ◽

Biogeochemical Models ◽

Ocean Carbon ◽

Vegetation Models ◽

Decadal Climate ◽

Global Vegetation

Measurements show large decadal variability in the rate of CO2 accumulation in the atmosphere that is not driven by CO2 emissions. The decade of the 1990s experienced enhanced carbon accumulation in the atmosphere relative to emissions, while in the 2000s, the atmospheric growth rate slowed, even though emissions grew rapidly. These variations are driven by natural sources and sinks of CO2 due to the ocean and the terrestrial biosphere. In this study, we compare three independent methods for estimating oceanic CO2 uptake and find that the ocean carbon sink could be responsible for up to 40% of the observed decadal variability in atmospheric CO2 accumulation. Data-based estimates of the ocean carbon sink from pCO2 mapping methods and decadal ocean inverse models generally agree on the magnitude and sign of decadal variability in the ocean CO2 sink at both global and regional scales. Simulations with ocean biogeochemical models confirm that climate variability drove the observed decadal trends in ocean CO2 uptake, but also demonstrate that the sensitivity of ocean CO2 uptake to climate variability may be too weak in models. Furthermore, all estimates point toward coherent decadal variability in the oceanic and terrestrial CO2 sinks, and this variability is not well-matched by current global vegetation models. Reconciling these differences will help to constrain the sensitivity of oceanic and terrestrial CO2 uptake to climate variability and lead to improved climate projections and decadal climate predictions.

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Stability Analysis of Rotor-Bearing Systems under the Influence of Misalignment and Parameter Uncertainty

Applied Sciences ◽

10.3390/app11177918 ◽

2021 ◽

Vol 11 (17) ◽

pp. 7918

Author(s):

Xiaodong Sun ◽

Kian K. Sepahvand ◽

Steffen Marburg

Keyword(s):

Computation Time ◽

Parametric Uncertainty ◽

Parameter Uncertainties ◽

Misalignment Effect ◽

Stability Threshold ◽

Rotating Systems ◽

Rotor Bearing ◽

Run Up ◽

The Stability ◽

The Impact

Stability is a well-known challenge for rotating systems supported by hydrodynamic bearings (HDBs), particularly for the condition where the misalignment effect and the parametric uncertainty are considered. This study investigates the impact of misalignment and inherent uncertainties in bearings on the stability of a rotor-bearing system. The misalignment effect is approximately described by introducing two misaligned angles. The characteristics of an HDB, such as pressure distribution and dynamic coefficients, are calculated by the finite difference method (FDM). The stability threshold is evaluated as the intersection of run-up curve and borderline. Viscosity and clearance are considered as uncertain parameters. The generalized polynomial chaos (gPC) expansion is adopted to quantify the uncertainty in parameters by evaluating unknown coefficients. The unknown gPC coefficients are obtained by using the collocation method. The results obtained by the gPC expansion are compared with those of the Monte Carlo (MC) simulation. The results show that the characteristics of the HDB and the stability threshold are affected by misalignment and parameter uncertainties. As the uncertainty analysis using the gPC expansion is performed on a relatively small number of predefined collocation points compared with the large number of MC samples, the method is very efficient in terms of computation time.

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Changes in biogenic carbon flow in response to sea surface warming

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0812743106 ◽

2009 ◽

Vol 106 (17) ◽

pp. 7067-7072 ◽

Cited By ~ 167

Author(s):

Julia Wohlers ◽

Anja Engel ◽

Eckart Zöllner ◽

Petra Breithaupt ◽

Klaus Jürgens ◽

...

Keyword(s):

Organic Carbon ◽

Elevated Temperatures ◽

Dissolved Inorganic Carbon ◽

Marine Ecosystem ◽

Ocean Warming ◽

Carbon Flow ◽

Trophic Levels ◽

Marine Biota ◽

Biogeochemical Models ◽

Biogenic Carbon

The pelagic ocean harbors one of the largest ecosystems on Earth. It is responsible for approximately half of global primary production, sustains worldwide fisheries, and plays an important role in the global carbon cycle. Ocean warming caused by anthropogenic climate change is already starting to impact the marine biota, with possible consequences for ocean productivity and ecosystem services. Because temperature sensitivities of marine autotrophic and heterotrophic processes differ greatly, ocean warming is expected to cause major shifts in the flow of carbon and energy through the pelagic system. Attempts to integrate such biological responses into marine ecosystem and biogeochemical models suffer from a lack of empirical data. Here, we show, using an indoor-mesocosm approach, that rising temperature accelerates respiratory consumption of organic carbon relative to autotrophic production in a natural plankton community. Increasing temperature by 2–6 °C hence decreased the biological drawdown of dissolved inorganic carbon in the surface layer by up to 31%. Moreover, warming shifted the partitioning between particulate and dissolved organic carbon toward an enhanced accumulation of dissolved compounds. In line with these findings, the loss of organic carbon through sinking was significantly reduced at elevated temperatures. The observed changes in biogenic carbon flow have the potential to reduce the transfer of primary produced organic matter to higher trophic levels, weaken the ocean's biological carbon pump, and hence provide a positive feedback to rising atmospheric CO2.

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Dependency of Feedbacks on Forcing and Climate State in Physics Parameter Ensembles

Journal of Climate ◽

10.1175/2011jcli3954.1 ◽

2011 ◽

Vol 24 (24) ◽

pp. 6440-6455 ◽

Cited By ~ 46

Author(s):

Masakazu Yoshimori ◽

Julia C. Hargreaves ◽

James D. Annan ◽

Tokuta Yokohata ◽

Ayako Abe-Ouchi

Keyword(s):

Last Glacial Maximum ◽

Climate Sensitivity ◽

Glacial Maximum ◽

Lapse Rate ◽

Climate Projections ◽

Parameter Uncertainties ◽

State Dependency ◽

Last Glacial ◽

The Last Glacial Maximum ◽

The Last Glacial

Abstract Climate sensitivity is one of the most important metrics for future climate projections. In previous studies the climate of the last glacial maximum has been used to constrain the range of climate sensitivity, and similarities and differences of temperature response to the forcing of the last glacial maximum and to idealized future forcing have been investigated. The feedback processes behind the response have not, however, been fully explored in a large model parameter space. In this study, the authors first examine the performance of various feedback analysis methods that identify important feedbacks for a physics parameter ensemble in experiments simulating both past and future climates. The selected methods are then used to reveal the relationship between the different ensemble experiments in terms of individual feedback processes. For the first time, all of the major feedback processes for an ensemble of paleoclimate simulations are evaluated. It is shown that the feedback and climate sensitivity parameters depend on the nature of the forcing and background climate state. The forcing dependency arises through the shortwave cloud feedback while the state dependency arises through the combined water vapor and lapse-rate feedback. The forcing dependency is, however, weakened when the feedback is estimated from the forcing that includes tropospheric adjustments. Despite these dependencies, past climate can still be used to provide a useful constraint on climate sensitivity as long as the limitation is properly taken into account because the strength of each feedback correlates reasonably well between the ensembles. It is, however, shown that the physics parameter ensemble does not cover the range of results simulated by structurally different models, which suggests the need for further study exploring both structural and parameter uncertainties.

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Dynamic Neural Network-Based Adaptive Tracking Control for an Autonomous Underwater Vehicle Subject to Modeling and Parametric Uncertainties

Applied Sciences ◽

10.3390/app11062797 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2797

Author(s):

Filiberto Muñoz ◽

Jorge S. Cervantes-Rojas ◽

Jose M. Valdovinos ◽

Omar Sandre-Hernández ◽

Sergio Salazar ◽

...

Keyword(s):

Degrees Of Freedom ◽

Neural Control ◽

Autonomous Underwater Vehicle ◽

Parametric Uncertainty ◽

Underwater Vehicle ◽

Added Mass ◽

Parametric Estimation ◽

Parameter Uncertainties ◽

External Disturbances ◽

Adaptive Tracking Control

This research presents a way to improve the autonomous maneuvering capability of a four-degrees-of-freedom (4DOF) autonomous underwater vehicle (AUV) to perform trajectory tracking tasks in a disturbed underwater environment. This study considers four second-order input-affine nonlinear equations for the translational (x,y,z) and rotational (heading) dynamics of a real AUV subject to hydrodynamic parameter uncertainties (added mass and damping coefficients), unknown damping dynamics, and external disturbances. We proposed an identification-control scheme for each dynamic named Dynamic Neural Control System (DNCS) as a combination of an adaptive neural controller based on nonparametric identification of the effect of unknown dynamics and external disturbances, and on parametric estimation of the added mass dependent input gain. Several numerical simulations validate the satisfactory performance of the proposed DNCS tracking reference trajectories in comparison with a conventional feedback controller with no adaptive compensation. Some graphics showing dynamic approximation of the lumped disturbance as well as estimation of the parametric uncertainty are depicted, validating effective operation of the proposed DNCS when the system is almost completely unknown.

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Quantifying the Impact of Parametric Uncertainty on Automatic Mechanism Generation for CO2 Hydrogenation on Ni(111)

10.26434/chemrxiv.14376899.v1 ◽

2021 ◽

Author(s):

Bjarne Kreitz ◽

C. Franklin Goldsmith ◽

Richard West ◽

Emily Mazeau ◽

Katrin Blondal ◽

...

Keyword(s):

Rate Control ◽

Parametric Uncertainty ◽

Co2 Hydrogenation ◽

Sensitivity Analyses ◽

Control Analysis ◽

Co2 Methanation ◽

Model Predictions ◽

Automatic Mechanism ◽

Global Uncertainty ◽

The Impact

Automatic mechanism generation is used to determine mechanisms for the CO2 hydrogenation on Ni(111) in a two-stage process, while considering the uncertainty in energetic parameters systematically. In a coarse stage, all the possible chemistry is explored with gas-phase products down to the ppb level, while a refined stage discovers the core methanation submechanism. 5,000 unique mechanisms were generated, which contain minor perturbations in all parameters. Global uncertainty assessment, global sensitivity analysis, and degree of rate control analysis are performed to study the effect 1 of this parametric uncertainty on the microkinetic model predictions. Comparison of the model predictions with experimental data on a Ni/SiO2 catalyst find a feasible set of microkinetic mechanisms that are in quantitative agreement with the measured data, without relying on explicit parameter optimization. Global uncertainty and sensitivity analyses provide tools to determine the pathways and key factors that control the methanation activity within the parameter space. Together, these methods reveal that the degree of rate control approach can be misleading if parametric uncertainty is not considered. The procedure of considering uncertainties in the automated mechanism generation is not unique to CO2 methanation and can be easily extended to other challenging heterogeneously catalyzed reactions<br>

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Ideas and perspectives: climate-relevant marine biologically driven mechanisms in Earth system models

Biogeosciences ◽

10.5194/bg-14-403-2017 ◽

2017 ◽

Vol 14 (2) ◽

pp. 403-413 ◽

Cited By ~ 11

Author(s):

Inga Hense ◽

Irene Stemmler ◽

Sebastian Sonntag

Keyword(s):

Atmospheric Composition ◽

Climate Projections ◽

Marine Biota ◽

Earth System ◽

System Models ◽

The Earth ◽

Optical And Mechanical Properties ◽

System 1 ◽

Earth System Models

Abstract. The current generation of marine biogeochemical modules in Earth system models (ESMs) considers mainly the effect of marine biota on the carbon cycle. We propose to also implement other biologically driven mechanisms in ESMs so that more climate-relevant feedbacks are captured. We classify these mechanisms in three categories according to their functional role in the Earth system: (1) biogeochemical pumps, which affect the carbon cycling; (2) biological gas and particle shuttles, which affect the atmospheric composition; and (3) biogeophysical mechanisms, which affect the thermal, optical, and mechanical properties of the ocean. To resolve mechanisms from all three classes, we find it sufficient to include five functional groups: bulk phyto- and zooplankton, calcifiers, and coastal gas and surface mat producers. We strongly suggest to account for a larger mechanism diversity in ESMs in the future to improve the quality of climate projections.

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Economic evaluation of carbetocin as prophylaxis for postpartum hemorrhage in the Philippines

BMC Health Services Research ◽

10.1186/s12913-020-05834-x ◽

2020 ◽

Vol 20 (1) ◽

Author(s):

Jamaica Roanne Briones ◽

Pattarawalai Talungchit ◽

Montarat Thavorncharoensap ◽

Usa Chaikledkaew

Keyword(s):

Cost Effectiveness ◽

Societal Perspective ◽

Postpartum Hemorrhage ◽

Budget Impact ◽

Cost Effective ◽

The Philippines ◽

World Health ◽

Sensitivity Analyses ◽

Parameter Uncertainties ◽

Effective Choice

Abstract Background The World Health Organization (WHO) recommends oxytocin as the drug of choice for postpartum hemorrhage (PPH) prevention. However, the WHO has also recently considered carbetocin for PPH prevention, but only if carbetocin were a cost-effective choice in the country. Consequently, we determined the cost-effectiveness and budgetary impact of carbetocin against oxytocin in the Philippines. Methods A cost-utility analysis using a decision tree was done to compare the costs and outcomes of carbetocin with oxytocin for PPH prophylaxis among women undergoing either vaginal delivery (VD) or cesarean section (CS) in a six-week time horizon using a societal perspective. One-way and probabilistic sensitivity analyses were applied to investigate parameter uncertainties. Additionally, budget impact analysis was conducted using a governmental perspective. Results were presented as incremental cost-effectiveness ratio (ICER) using a 2895 United States dollar (USD) per quality adjusted life year (QALY) gained as the ceiling threshold in the Philippines. Results Carbetocin was not cost-effective given the listed price of carbetocin at 18 USD. Given a societal perspective, the ICER values of 13,187 USD and over 40,000 USD per QALY gained were derived for CS and VD, respectively. Moreover, the ICER values were sensitive to the risk ratio of carbetocin versus oxytocin and carbetocin price. On budget impact, the five-year total budget impact of a drug mix of carbetocin and oxytocin was 25.54 million USD (4.23 million USD for CS and 21.31 million USD for VD) compared with ‘only oxytocin’ scenario. Conclusion Carbetocin is not a cost-effective choice in PPH prevention for both modes of delivery in the Philippines, unless price reduction is made. Our findings can be used for evidence-informed policies to guide coverage decisions on carbetocin not only in the Philippines but also in other low and middle-income countries.

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Coupled physical/biogeochemical modeling including O<sub>2</sub>-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

Biogeosciences ◽

10.5194/bg-10-3559-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 3559-3591 ◽

Cited By ~ 33

Author(s):

E. Gutknecht ◽

I. Dadou ◽

B. Le Vu ◽

G. Cambon ◽

J. Sudre ◽

...

Keyword(s):

Sensitivity Analyses ◽

Global Ocean ◽

Biogeochemical Model ◽

Ammonium Oxidation ◽

N Loss ◽

Total N ◽

Eastern Boundary ◽

Parameter Values ◽

The Impact ◽

Oxygen Concentrations

Abstract. The Eastern Boundary Upwelling Systems (EBUS) contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs), EBUS represent key regions for the oceanic nitrogen (N) cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O) occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS) taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela) using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2− oxidation, NO3− reduction, and anammox) as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen concentrations are driven by the poleward meridional advection of oxygen-depleted waters offshore of a 300 m isobath and by the biogeochemical activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia. In the OMZ off Namibia, the magnitude of N2O outgassing and of N loss is comparable. Anammox contributes to about 20% of total N loss, an estimate lower than currently assumed (up to 50%) for the global ocean.

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