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Statistical analysis of factors driving surface ozone variability over continental South Africa

JOURNAL OF INTEGRATIVE ENVIRONMENTAL SCIENCES 2020年第3期17卷 1-28页

作者： Laban, Tracey Leah Van Zyl, Pieter Gideon Beukes, Johan Paul Mikkonen, Santtu Santana, Leonard Josipovic, Miroslav Vakkari, Ville Thompson, Anne M. Kulmala, Markku Laakso, Lauri North West Univ Chem Resource Beneficiat Potchefstroom South Africa Univ Eastern Finland Dept Appl Phys Kuopio Finland North West Univ Sch Math & Stat Sci Potchefstroom South Africa Finnish Meteorol Inst Helsinki Finland NASA Goddard Space Flight Ctr Earth Sci Div Greenbelt MD USA Univ Helsinki Dept Phys Helsinki Finland

Statistical relationships between surface ozone (O-3) concentration, precursor species and meteorological conditions in continental South Africa were examined from data obtained from measurement stations in north-eastern South Africa. Three multivariate statistical methods were applied in the investigation, i.e. multiple linear regression (MLR), principal component analysis (PCA) and -regression (PCR), and generalised additive model (GAM) analysis. The daily maximum 8-h moving average O-3 concentrations were considered in these statistical models (dependent variable). MLR models indicated that meteorology and precursor species concentrations are able to explain similar to 50% of the variability in daily maximum O-3 levels. MLR analysis revealed that atmospheric carbon monoxide (CO), temperature and relative humidity were the strongest factors affecting the daily O-3 variability. In summer, daily O-3 variances were mostly associated with relative humidity, while winter O-3 levels were mostly linked to temperature and CO. PCA indicated that CO, temperature and relative humidity were not strongly collinear. GAM also identified CO, temperature and relative humidity as the strongest factors affecting the daily variation of O-3. Partial residual plots found that temperature, radiation and nitrogen oxides most likely have a non-linear relationship with O-3,while the relationship with relative humidity and CO is probably linear. An inter-comparison between O-3 levels modelled with the three statistical models compared to measured O-3 concentrations showed that the GAM model offered a slight improvement over the MLR model. These findings emphasise the critical role of regional-scale O-3 precursors coupled with meteorological conditions in daily variances of O-3 levels in continental South Africa.

关键词： Tropospheric ozone (O-3) multiple linear regression principal component analysis generalized additive models Welgegund

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Twenty-eight years of vowels: Tracking phonetic variation through young to middle age adulthood

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JOURNAL OF PHONETICS 2019年 74卷 42-54页

作者： Gahl, Susanne Baayen, R. Harald Univ Calif Berkeley Dept Linguist Berkeley CA 94704 USA Eberhard Karls Univ Tubingen Tubingen Germany

Research on age-related changes in speech has primarily focused on comparing "young" vs. "elderly" adults. Yet, listeners are able to guess talker age more accurately than a binary distinction would imply, suggesting that acoustic characteristics of speech change continually and gradually throughout adulthood. We describe acoustic properties of vowels produced by eleven talkers based on naturalistic speech samples spanning a period of 28 years, from ages 21 to 49. We find that the position of vowels in F1/F2 space shifts towards the periphery with increasing talker age. eased on generalized additive Mixed Effects models, we show that this shift is not fully attributable to changes in vowel duration or to segmental context. We discuss the implications of our results for research on aging and speech, and for research in which durational shortening and spectral characteristics of vowels are assumed to reflect a unitary process of phonetic reduction. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Phonetic reduction Vowels Vowel duration Vowel formants Talker age generalized additive models

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Opportunistic shirking behaviour during unpaid overtime

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APPLIED ECONOMICS LETTERS 2019年第7期26卷 608-612页

作者： Lopez, Michael J. Mills, Brian M. Dept Math & Stat Saratoga Springs NY 12866 USA Univ Florida Coll Hlth & Human Performance Dept Tourism Recreat & Sport Management Gainesville FL USA

We identify the presence of shirking by Major League Baseball umpires during indefinite unpaid overtime, as defined by extra innings. In the presence of new information about expected game length, umpires exert biases in ball and strike calls consistent with opportunistically reducing the likelihood of working additional time. General implications with respect to the effectiveness of salaried workers during unpaid overtime hours are discussed.

关键词： Shirking personnel economics baseball generalized additive models

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generalized additive models and inflated type I error rates of smoother significance tests

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COMPUTATIONAL STATISTICS & DATA ANALYSIS 2011年第1期55卷 366-374页

作者： Young, Robin L. Weinberg, Janice Vieira, Veronica Al Ozonoff Webster, Thomas F. Boston Univ Dept Biostat Sch Publ Hlth Boston MA 02118 USA Boston Univ Dept Environm Hlth Sch Publ Hlth Boston MA 02118 USA

generalized additive models (GAMs) have distinct advantages over generalized linear models as they allow investigators to make inferences about associations between outcomes and predictors without placing parametric restrictions on the associations. The variable of interest is often smoothed using a locally weighted scatterplot smoothing (LOESS) and the optimal span (degree of smoothing) can be determined by minimizing the Akaike Information Criterion (AIC). A natural hypothesis when using GAMs is to test whether the smoothing term is necessary or if a simpler model would suffice. The statistic of interest is the difference in deviances between models including and excluding the smoothed term. As approximate chi-square tests of this hypothesis are known to be biased, permutation tests are a reasonable alternative. We compare the type I error rates of the chi-square test and of three permutation test methods using synthetic data generated under the null hypothesis. In each permutation method a distribution of differences in deviances is obtained from 999 permuted datasets and the null hypothesis is rejected if the observed statistic falls in the upper 5% of the distribution. One test is a conditional permutation test using the optimal span size for the observed data;this span size is held constant for all permutations. This test is shown to have an inflated type I error rate. Alternatively, the span size can be fixed a priori such that the span selection technique is not reliant on the observed data. This test is shown to be unbiased;however, the choice of span size is not clear. A third method is an unconditional permutation test where the optimal span size is selected for observed and permuted datasets. This test is unbiased though computationally intensive. (C) 2010 Elsevier B.V. All rights reserved.

关键词： generalized additive models Type I error Permutation test Span size selection

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Fish Communities on Natural and Artificial Reefs in the Eastern Gulf of Mexico

Fish Communities on Natural and Artificial Reefs in the East...

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作者： Viau, Elizabeth C. University of South Florida

学位级别：M.S.

Artificial reefs have been deployed throughout the world’s oceans to act as habitat and fishing enhancement tools. To expand current research on the role of artificial reefs in the marine community, ordination and multivariate regression methods were used here to analyze survey data of natural and artificial reefs. The reefs, located in the Northern Gulf of Mexico (NGOM) and on the West Florida Shelf (WFS), had been previously surveyed from 2004 to 2015 using remote operated vehicle and stationary video techniques. This study tested the hypothesis that similar functional roles are accounted for at both natural and artificial reef sites even if species composition varies. Secondly, it examines the role of environment and fisheries in determining the assemblages. Artificial reefs tended to host communities that were as biodiverse as natural reefs, although not necessarily composed of the same species. Results of an ordination confirmed that as the classification was broadened from the level of species, to family, to functional group, the assemblages on each reef type (natural vs. artificial and NGOM vs WFS) appeared more similar. Dominant groups were present at all levels of classification and included the families Lutjanidae and Carangidae, as well as functional groups Red Snapper and Small Reef Fish. Both natural and artificial reefs tended to be dominated by one of the following: Lutjanidae, Carangidae, or Small Reef Fish, although a continuous gradient was found across the extremes of natural versus artificial reefs. generalized additive models were developed to examine the influence of reef type, location, environment and fishing intensity covariates. Results indicated that for both natural and artificial reefs, the abundance of families and functional groups can be influenced by environmental factors. In both cases, there is strong spatial autocorrelation suggesting connectivity with neighboring reefs.

关键词： Lutjanidae Carangidae generalized additive models West Florida Shelf Northern Gulf of Mexico Artificial Reefs

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Addressing spatio-temporal resolution constraints in Landsat and MODIS-based mapping of large-scale floodplain inundation dynamics

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REMOTE SENSING OF ENVIRONMENT 2018年 211卷 307-320页

作者： Heimhuber, V. Tulbure, M. G. Broich, M. Univ New South Wales Sch Biol Earth & Environm Sci Sydney NSW Australia

Recent studies have developed novel long-term records of surface water (SW) maps on continental and global scales but due to the spatial and temporal resolution constraints of available satellite sensors, they are either of high spatial and low temporal resolution or vice versa. In this study, we address this limitation by exploring two approaches for generating an 8-day series of Landsat resolution (30 m) SW maps for three floodplain sites in south-eastern Australia during the 2010 La Nina Floods. Firstly, we applied a generalized additive regression model (GAM) that empirically relates Landsat-based SW extent to in-situ river flow to then predict additional time steps. Secondly, we used the STARFM and ESTARFM blending algorithms for predicting the Open Water Likelihood at 8-daily intervals and 30 m resolution from Landsat and MODIS imagery. ESTARFM outperformed STARFM and best blending accuracies were achieved in the floodplain site with the slowest changes in inundation extent through time. There was good agreement between the blended and statistically-modeled 8-day SW series and both series provided new and temporally consistent information about changes in inundation extent throughout the flooding cycles. After careful consideration of accuracy limitations and model assumptions, these SW records hold great potential for assimilation into hydrodynamic and hydrological models as well as improved management of terrestrial freshwater ecosystems.

关键词： Surface water mapping Landsat-MODIS blending STARFM ESTARFM generalized additive models

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Using a trait-based approach to optimize mixotrophic growth of the red microalga Porphyridium purpureum towards fatty acid production

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BIOTECHNOLOGY FOR BIOFUELS 2018年第1期11卷 1-11页

作者： Jiao, Kailin Xiao, Wupeng Xu, Yuanchao Zeng, Xianhai Ho, Shih-Hsin Laws, Edward A. Lu, Yinghua Ling, Xueping Shi, Tuo Sun, Yong Tang, Xing Lin, Lu Xiamen Univ Coll Energy Xiamen 361102 Peoples R China Xiamen Univ Fujian Prov Key Lab Coastal Ecol & Environm Studi State Key Lab Marine Environm Sci Xiamen 361102 Peoples R China Qilu Univ Technol Shandong Acad Sci Shangdong Prov Key Lab Microbial Engn Jinan 250353 Shandong Peoples R China Xiamen Univ Fujian Engn & Res Ctr Clean & High Valued Convers Xiamen Key Lab Clean & High Valued Convers Techno Xiamen 361102 Peoples R China Harbin Inst Technol Sch Environm State Key Lab Urban Water Resource & Environm Harbin 150006 Heilongjiang Peoples R China Louisiana State Univ Sch Coast & Environm Dept Environm Sci Baton Rouge LA 70803 USA Xiamen Univ Coll Chem & Chem Engn Dept Chem & Biochem Engn Xiamen 361005 Peoples R China

Background: Organic carbon sources have been reported to simultaneously increase the growth and lipid accumulation in microalgae. However, there have been no studies of the mixotrophic growth of Porphyridium purpureum in organic carbon media. In this study, three organic carbon sources, glucose, sodium acetate, and glycerol were used as substrates for the mixotrophic growth of P. purpureum. Moreover, a novel trait-based approach combined with generalized additive Modeling was conducted to determine the dosage of each organic carbon source that optimized the concentration of cell biomass or fatty acid. Results: A 0.50% (w/v) dosage of glucose was optimum for the enhancement of the cell growth of P. purpureum, whereas sodium acetate performed well in enhancing cell growth, arachidonic acid (ARA) and eicosapentaenoic acid (EPA) content, and glycerol was characterized by its best performance in promoting both cell growth and ARA/EPA ratio. The optimum dosages of sodium acetate and glycerol for the ARA concentration were 0.25% (w/v) and 0.38% (v/v), respectively. An ARA concentration of 211.47 mg L-1 was obtained at the optimum dosage of glycerol, which is the highest ever reported. Conclusions: The results suggested that a comprehensive consider of several traits offers an effective strategy to select an optimum dosage for economic and safe microalgae cultivation. This study represents the first attempt of mixotrophic growth of P. purpureum and proved that both biomass and ARA accumulation could be enhanced under supplements of organic carbon sources, which brightens the commercial cultivation of microalgae for ARA production.

关键词： Porphyridium purpureum Arachidonic acid Organic carbon generalized additive models Trait-based approach

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Analyzing fine-scale spatiotemporal drivers of wildfire in a forest landscape model

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ECOLOGICAL MODELLING 2018年 384卷 87-102页

作者： Ager, Alan A. Barros, Ana M. G. Day, Michelle A. Preisler, Haiganoush K. Spies, Thomas A. Bolte, John US Forest Serv USDA Rocky Mt Res Stn Missoula Fire Sci Lab 5775 US Highway 10W Missoula MT 59808 USA Oregon State Univ Coll Forestry Forest Ecosyst & Soc 321 Richardson Hall Corvallis OR 97331 USA Oregon State Univ Coll Forestry Forest Engn Resources & Management 280 Peavey Hall Corvallis OR 97331 USA US Forest Serv USDA Pacific Southwest Res Stn 800 Buchanan St Albany CA 94710 USA US Forest Serv USDA Pacific Northwest Res Stn 3200 SW Jefferson Way Corvallis OR 97331 USA Oregon State Univ Dept Biol Engn Corvallis OR 97331 USA

We developed and applied a wildfire simulation package in the Envision agent-based landscape modelling system. The wildfire package combines statistical modelling of fire occurrence with a high-resolution, mechanistic wildfire spread model that can capture fine scale effects of fire feedbacks and fuel management, and replicate restoration strategies at scales that are meaningful to forest managers. We applied the model to a landscape covering 1.2 million ha of fire prone area in central Oregon, USA where wildland fires are increasingly impacting conservation, amenity values and developed areas. We conducted simulations to examine the effect of human versus natural ignitions on future fire regimes under current restoration programs, and whether contemporary fire regimes observed in the past 20 years are likely to change as result of fire feedbacks and management activities. The ignition prediction model revealed non-linear effects of location and time of year, and distinct spatiotemporal patterns for human versus natural ignitions. Fire rotation interval among replicate simulations varied from 78 to 170 years and changed little over the 50-yr simulation, suggesting a stable but highly variable and uncertain future fire regime. Interestingly, the potential for fire-on-fire feedbacks was higher for human versus natural ignitions due to human ignition hotspots within the study area. We compare the methods and findings with other forest landscape simulation model (FLSM) studies and discuss future application of FLSMs to address emerging wildfire management and policy issues on fire frequent forests in the western US.

关键词： Agent-Based modelling Envision Landscape modelling Forest management modelling Wildfire modelling generalized additive models

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Association of ground-level ozone, meteorological factors and weather types with daily myocardial infarction frequencies in Augsburg, Southern Germany

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ATMOSPHERIC ENVIRONMENT 2019年 217卷

作者： Hertig, Elke Schneider, Alexandra Peters, Annette von Scheidt, Wolfgang Kuch, Bernhard Meisinger, Christa Univ Augsburg Inst Geog Alter Postweg 118 D-86135 Augsburg Germany Univ Augsburg Fac Med Alter Postweg 118 D-86135 Augsburg Germany Helmholtz Zentrum Munchen Inst Epidemiol German Res Ctr Environm Hlth GmbH Neuherberg Germany Ludwig Maximilian Univ Munchen Inst Med Informat Proc Biometry & Epidemiol Munich Germany German Res Ctr Cardiovasc Res DZHK Partner Site Munich Munich Germany Univ Hosp Augsburg Dept Internal Med 1 Cardiol Augsburg Germany Hosp Nordlingen Nordlingen Germany Ludwig Maximilian Univ Munchen Chair Epidemiol UNIKA T Munich Germany Helmholtz Zentrum Munchen Independent Res Grp Clin Epidemiol Munich Germany

The first part of the present study addresses meteorological and synoptic factors governing daily maximum 1-hour ozone (O-3) concentrations in the city of Augsburg in the months from March to September. In the second part statistical models are applied to assess the association between daily myocardial infarction (MI) frequencies and ozone exposure, under the additional consideration of climatic and synoptic factors. Daily maximum 1-hour ozone concentrations were increased with high air temperatures, low values of specific humidity and high ozone concentrations of the previous day. Besides, four weather types were connected with ozone, the weather type "U", which describes mainly low-flow conditions, being of particular importance. The daily maximum 1-hour ozone concentrations showed a notable non-linear relationship with MI frequencies in Augsburg. An enhanced MI risk occurred mainly at median to moderately high ozone concentrations. A piecewise linear regression up to the maximum relative risk at approximately the 75%-ozone percentile (116 mu g/m(3)) yielded a significant increase of 3.41% (95% confidence interval: [1.33%, 5.53%]) of the MI frequency per 10 pg/m 3 increase in ozone. At higher ozone concentrations a decrease of the MI risk occurred. Three weather types were selected as additional predictors in the statistical models. Most notable was the frequent weather type Anticyclonic (A), which is related to a reduction in MI frequencies.

关键词： Ground-level ozone Meteorology Weather types Myocardial infarction Lasso regression generalized additive models

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Realized niches explain spatial gradients in seasonal abundance of phytoplankton groups in the South China Sea

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PROGRESS IN OCEANOGRAPHY 2018年 162卷 223-239页

作者： Xiao, Wupeng Wang, Lei Laws, Edward Xie, Yuyuan Chen, Jixin Liu, Xin Chen, Bingzhang Huang, Bangqin Xiamen Univ Fujian Prov Key Lab Coastal Ecol & Environm Studi State Key Lab Marine Environm Sci Xiamen Peoples R China State Ocean Adm Inst Oceanog 3 Lab Marine Biol & Ecol Xiamen Peoples R China Louisiana State Univ Sch Coast & Environm Dept Environm Sci Baton Rouge LA 70803 USA Japan Agcy Marine Earth Sci & Technol Res & Dev Ctr Global Change Ecosyst Dynam Res Grp Yokohama Kanagawa Japan

A basic albeit elusive goal of ocean science is to predict the structure of biological communities from the multitude of environmental conditions they experience. Estimates of the realized niche-based traits (realized traits) of phytoplankton species or functional groups in temperate seas have shown that response traits can help reveal the mechanisms responsible for structuring phytoplankton communities, but such approaches have not been tested in tropical and subtropical marginal seas. Here, we used decadal-scale studies of pigment-based phytoplankton groups and environmental conditions in the South China Sea to test whether realized traits could explain the biogeographic patterns of phytoplankton variability. We estimated the mean and breadth of the phytoplankton realized niches based on responses of the group-specific phytoplankton composition to key environmental factors, and we showed that variations of major phytoplankton groups in this system can be explained by different adaptive trade-offs to constraints imposed by temperature, irradiance, and nutrient concentrations. Differences in the patterns of trade-offs clearly separated the dominant groups from one another and generated four sets of realized traits that mirrored the observed biogeographic distribution patterns. The phytoplankton realized niches and their associated traits that we characterized in the present study could help to predict responses of phytoplankton to changes in environmental conditions in the South China Sea and could be incorporated into global biogeochemical models to anticipate shifts in community structure under future climate scenarios.

关键词： Phytoplankton Realized niches Realized traits generalized additive models MaxEnt modelling South China Sea

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