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  • 1
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    Bayesian parameter estimation and interpretation for an intermediate model of tree-ring width (2013)
    Copernicus Publications on behalf of the European Geosciences Union
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Climate of the Past 9 (2013): 1481-1493, doi:10.5194/cp-9-1481-2013.
    Description: We present a Bayesian model for estimating the parameters of the VS-Lite forward model of tree-ring width for a particular chronology and its local climatology. The scheme also provides information about the uncertainty of the parameter estimates, as well as the model error in representing the observed proxy time series. By inferring VS-Lite's parameters independently for synthetically generated ring-width series at several hundred sites across the United States, we show that the algorithm is skillful. We also infer optimal parameter values for modeling observed ring-width data at the same network of sites. The estimated parameter values covary in physical space, and their locations in multidimensional parameter space provide insight into the dominant climatic controls on modeled tree-ring growth at each site as well as the stability of those controls. The estimation procedure is useful for forward and inverse modeling studies using VS-Lite to quantify the full range of model uncertainty stemming from its parameterization.
    Description: This work was supported in part by an American Association of University Women Dissertation Fellowship and grants NSF ATM-0724802, NSF ATM-0902715, NSF DMS- 1204892, and NOAA NA060OAR4310115.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/zip
    Format: application/pdf
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  • 2
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    Applications of proxy system modeling in high resolution paleoclimatology (2013)
    Elsevier B.V.
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Quaternary Science Reviews 76 (2013): 16-28, doi:10.1016/j.quascirev.2013.05.024.
    Description: A proxy system model may be defined as the complete set of forward and mechanistic processes by which the response of a sensor to environmental forcing is recorded and subsequently observed in a material archive. Proxy system modeling complements and sharpens signal interpretations based solely on statistical analyses and transformations; provides the basis for observing network optimization, hypothesis testing, and data-model comparisons for uncertainty estimation; and may be incorporated as weak but mechanistically-plausible constraints into paleoclimatic reconstruction algorithms. Following a review illustrating these applications, we recommend future research pathways, including development of intermediate proxy system models for important sensors, archives, and observations; linking proxy system models to climate system models; hypothesis development and evaluation; more realistic multi-archive, multi-observation network design; examination of proxy system behavior under extreme conditions; and generalized modeling of the total uncertainty in paleoclimate reconstructions derived from paleo-observations.
    Description: MNE and DMT were funded by NOAA/C2D2 grant NA10OAR4310115; SETW gratefully acknowledges support from an American Association of UniversityWomen Dissertation Fellowship. Work cited in this review was supported by NSF grants 0349356, 0724802 and 0902715, NOAA grants NA06OAR4310115 and NA08OAR4310682, and the University of Arizona’s Department of Geosciences and Institute of the Environment.
    Keywords: Forward modeling ; Observational network optimization ; Data-model comparison ; Hypothesis evaluation ; Reconstruction ; Uncertainty modeling
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Predicting hygroscopic growth using single particle chemical composition estimates (2014)
    Wiley-Blackwell
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    Publication Date: 2014-07-25
    Description: Single particle mass spectral data, collected in Paris, France during the MEGAPOLI winter campaign, have been used to predict hygroscopic growth at the single particle level. The mass fractions of black carbon, organic aerosol, ammonium, nitrate and sulphate present in each particle were estimated using a combination of single particle mass spectrometer and bulk aerosol chemical composition measurements. The Zdanovskii-Stokes-Robinson (ZSR) approach was then applied to predict hygroscopic growth factors based on these mass fraction estimates. Smaller particles with high black carbon mass fractions and low inorganic ion mass fractions exhibited the lowest predicted growth factors, while larger particles with high inorganic ion mass fractions exhibited the highest growth factors. Growth factors were calculated for subsaturated relative humidity (90%) to enable comparison with hygroscopic tandem differential mobility analyser (HTDMA) measurements. Mean predicted and measured hygroscopic growth factors for 110, 165 and 265 nm particles were found to agree within 6%. Single particle-based ZSR hygroscopicity estimates offer an advantage over bulk aerosol composition-based hygroscopicity estimates by providing additional chemical mixing state information. External mixing can be determined for particles of a given diameter through examination of the predicted hygroscopic growth factor distributions. 110 nm and 265 nm particles were found to be predominantly internally mixed using this approach, however external mixing of 165 nm particles was observed periodically when thinly coated and thickly coated BC particles were simultaneously detected. Single particle-resolved chemical information will be useful for modelling efforts aimed at constraining cloud condensation nuclei activity and hygroscopic growth.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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  • 4
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    Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada (2013)
    BioMed Central
    Details
    Publication Date: 2013-04-05
    Description: Background: Herbivore coexistence on the Late Cretaceous island continent of Laramidia has been a topic of great interest, stemming from the paradoxically high diversity and biomass of these animals in relation to the relatively small landmass available to them. Various hypotheses have been advanced to account for these facts, of which niche partitioning is among the most frequently invoked. However, despite its wide acceptance, this hypothesis has not been rigorously tested. This study uses the fossil assemblage from the Dinosaur Park Formation of Alberta as a model to investigate whether niche partitioning facilitated herbivorous dinosaur coexistence on Laramidia. Specifically, the question of feeding height stratification is examined in light of the role it plays in facilitating modern ungulate coexistence. Results: Most herbivorous dinosaur species from the Dinosaur Park Formation were restricted to feeding no higher than approximately 1 m above the ground. There is minimal evidence for feeding height partitioning at this level, with ceratopsids capable of feeding slightly higher than ankylosaurs, but the ecological significance of this is ambiguous. Hadrosaurids were uniquely capable of feeding up to 2 m quadrupedally, or up to 5 m bipedally. There is no evidence for either feeding height stratification within any of these clades, or for change in these ecological relationships through the approximately 1.5 Ma record of the Dinosaur Park Formation. Conclusions: Although we cannot reject the possibility, we find no good evidence that feeding height stratification, as revealed by reconstructed maximum feeding heights, played an important role in facilitating niche partitioning among the herbivorous dinosaurs of Laramdia. Most browsing pressure was concentrated in the herb layer, although hadrosaurids were capable of reaching shrubs and low-growing trees that were out of reach from ceratopsids, ankylosaurs, and other small herbivores, effectively dividing the herbivores in terms of relative abundance. Sympatric hadrosaurids may have avoided competing with one another by feeding differentially using bipedal and quadrupedal postures. These ecological relationships evidently proved to be evolutionarily stable because they characterize the herbivore assemblage of the Dinosaur Park Formation through time. If niche partitioning served to facilitate the rich diversity of these animals, it may have been achieved by other means in addition to feeding height stratification. Consideration of other feeding height proxies, including dental microwear and skull morphology, may help to alleviate problems of underdetermination identified here.
    Electronic ISSN: 1472-6785
    Topics: Biology
    Published by BioMed Central
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  • 5
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    A Rheological and Chemical Investigation of Canadian Heavy Oils From the McMurray Formation (2012)
    American Chemical Society (ACS)
    Details
    Publication Date: 2012-06-28
    Description: Energy & Fuels DOI: 10.1021/ef300608w
    Print ISSN: 0887-0624
    Electronic ISSN: 1520-5029
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Process Engineering, Biotechnology, Nutrition Technology
    Published by American Chemical Society (ACS)
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