Multivariate Bayesian analysis of atmosphere–ocean general circulation models

Numerical experiments based on atmosphere–ocean general circulation models (AOGCMs) are one of the primary tools in deriving projections for future climate change. Although each AOGCM has the same underlying partial differential equations modeling large scale effects, they have different small scale parameterizations and different discretizations to solve the equations, resulting in different climate projections. This motivates climate projections synthesized from results of several AOGCMs’ output. We combine present day observations, present day and future climate projections in a single highdimensional hierarchical Bayes model. The challenging aspect is the modeling of the spatial processes on the sphere, the number of parameters and the amount of data involved. We pursue a Bayesian hierarchical model that separates the spatial response into a large scale climate change signal and an isotropic process representing small scale variability among AOGCMs. Samples from the posterior distributions are obtained with computer-intensive MCMC simulations. The novelty of our approach is that we use gridded, high resolution data covering the entire sphere within a spatial hierarchical framework. The primary data source is provided by the Coupled Model Intercomparison Project (CMIP) and consists of 9 AOGCMs on a 2.8 by 2.8 degree grid under several different emission scenarios. In this article we consider mean seasonal surface temperature and precipitation as climate variables. Extensions to our model are also discussed.     

Serum concentrations of perfluorooctanesulfonate and other fluorochemicals in an elderly population from Seattle, Washington

Perfluorooctanesulfonyl fluoride (POSF, C₈F₁₇SO₂F) related-materials have been used as surfactants, paper and packaging treatments, and surface (e.g., carpet, textile, upholstery) protectants. A metabolite, perfluorooctanesulfonate (PFOS, C₈F₁₇SO₃⁻), has been identified in the serum and liver of non-occupationally exposed humans and wildlife. Because of its persistence, an important question was whether elderly humans might have higher PFOS concentrations. From a prospective study designed to examine cognitive function in the Seattle (WA) metropolitan area, blood samples were collected from 238 dementia-free subjects (ages 65–96). High-pressure liquid chromatography-electrospray tandem mass spectrometry determined seven fluorochemicals: PFOS; N-ethyl perfluorooctanesulfonamidoacetate; N-methyl perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamide; perfluorooctanoate; and perfluorohexanesulfonate. Serum PFOS concentrations ranged from less than the lower limit of quantitation (3.4 ppb) to 175.0 ppb (geometric mean 31.0 ppb; 95% CI 28.8–33.4). An estimate of the 95% tolerance limit was 84.1 ppb (upper 95% confidence limit 104.0 ppb). Serum PFOS concentrations were slightly lower among the most elderly. There were no significant differences by sex or years residence in Seattle. The distributions of the other fluorochemicals were approximately an order of magnitude lower. Similar to other reported findings of younger adults, the geometric mean serum PFOS concentration in non-occupational adult populations likely approximates 30–40 ppb with 95% of the population’s serum PFOS concentrations below 100 ppb.     

Female choice for parasite-free male satin bowerbirds and the evolution of bright male plumage

Summary Hamilton and Zuk proposed that bright male plumage may have evolved in males of polygynous species as a result of female preferences for males that are able to demonstrate their resistance to disease. They predicted an inverse correlation between female mating preferences and the level of parasitic infection of males. We found such a correlation between the level of infection by a common ectoparasite (Myrsidea ptilonorhynchi: Menoponidae) and mating success of male satin bowerbirds (Ptilonorhynchus violaceus). In addition, we tested and were able to confirm three other predictions derived from their model: that (1) older males had fewer parasites than their younger counterparts, (2) levels of individual parasitic infection are highly correlated between years, and (3) that individuals resighted in successive years are less parasitized than those that fail to return. These results support the bright male model, but they are also consistent with two other hypotheses that may explain plumage dimorphism based on the level of parasitic infection. The correlated infection model suggests that females choose males with few ectoparasites because of a correlation between the level of ectoparasitic infection and heritable resistance to internal infections. In the parasite avoidance model, females favor parasitefree males because it lowers their own prospects for parasitic infection. Our data did not show the predicted relationship between parasite numbers with plumage quality that is needed to support the bright male hypothesis, nor did it show the inverse correlation between male condition and parasite numbers that is predicted by both the bright male and correlated infection hypotheses. Our results are most consistent with the parasite avoidance hypothesis.     

Environmentally stratified sampling design for the development of Great Lakes environmental indicators

Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for a population of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.     

Modeling the Effects of Air Quality Policy Changes on Water Quality in Urban Areas

This paper describes the development and application of an integrated modeling framework composed of an urban air chemistry model, an urban runoff model, and a water-quality model. The models were linked to simulate the fate and transport of air emissions of nitrogen compounds in the air, urban watershed, surface water runoff, and in a coastal receiving-water body. The model linkage is demonstrated by evaluating the potential water quality implications of reducing NO _x emissions by 32%, volatile organic compound emissions by 51%, and ammonia emissions by 30%, representing changes from 1987 levels to proposed 2000 target levels in Los Angeles, California, USA. Simulations of the Los Angeles dry season during the summer of 1987 (June 1 to August 31) indicated that by reducing emissions from 1987 to proposed year 2000 levels, the dry deposition nitrogen loads to Santa Monica Bay and the Ballona Creek watershed were reduced 21.4% and 15.0%, respectively. Water quality modeling results indicated that dry season atmospheric load reductions to the Ballona Creek Estuary did not reduce chlorophyll-a levels or significantly raise nighttime dissolved oxygen levels because the magnitude of the reductions was negligible compared to non-atmospheric inputs of nitrogen compounds. Simulations of the time period from November 18, 1987 to December 4, 1987 during the Los Angeles wet season indicated that air emissions reductions produced an 18.6% reduction in the dry deposition nitrogen load to Santa Monica Bay, a 15.5% reduction in the dry deposition nitrogen load to the Ballona Creek watershed, a 16.8% reduction in the wet deposition nitrogen load to the Ballona Creek watershed, and a 16.1% reduction in the stormwater discharge load from the Ballona Creek watershed. Although the wet season load reductions are significant, modeling results of the ultimate effect on the Ballona Creek Estuary water quality were inconclusive.     

Elemental Composition of Urban Aerosol Collected in Florence, Italy

An extensive investigation is in progress aiming at the characterisation of the air particulate composition in Florence. For our investigation, we use the external PIXE-PIGE beam facility of the I.N.F.N. Van de Graaff accelerator at the Physics Department of the Florence University. In order to gather information on both the longer- and shorter-time trends of the aerosol elemental composition, we are analysing both long temporal series (about 1 year) of 24-h Millipore filters collected by the health authorities in 3 different sites, and filters collected simultaneously in two of the above sites for about one month, by two streakers with one-hour resolution, providing size fractionation between particle size smaller than 2.5 µm and from 2.5 µm to 10 µm. The streakers sampling period includes two days during which the Municipality of Florence has banned the circulation of non-catalytic cars, due to the increase of NO₂ above the "recommended safety values". We present here the first obtained results for the sampling site located near a heavy traffic road.     

If Stationarity is Dead,What Do We Do Now?1

Galloway, Gerald E., 2011. If Stationarity Is Dead, What Do We Do Now? Journal of the American Water Resources Association (JAWRA) 47(3):563‐570. DOI: 10.1111/j.1752‐1688.2011.00550.x Abstract: In January 2010, hydrologists, climatologists, engineers, and scientists met in Boulder, Colorado, to discuss the report of the death of hydrologic stationarity and the implications this might have on water resources planning and operations in the United States and abroad. For decades planners have relied on design guidance from the Interagency Advisory Committee on Water Data Bulletin 17B that was based upon the concept of stationarity. After 2½ days of discussion it became clear that the assembled community had yet to reach an agreement on whether or not to replace the assumption of stationarity with an assumption of nonstationarity or something else. Hydrologists were skeptical that data gathered to this point in the 21st Century point to any significant change in river parameters. Climatologists, on the other hand, point to climate change and the predicted shift away from current conditions to a more turbulent flood and drought filled future. Both groups are challenged to provide immediate guidance to those individuals in and outside the water community who today must commit funds and efforts on projects that will require the best estimates of future conditions. The workshop surfaced many approaches to dealing with these challenges. While there is good reason to support additional study of the death of stationarity, its implications, and new approaches, there is also a great need to provide those in the field the information they require now to plan, design, and operate today’s projects.     

Design of Sampling Schedules

Concern with the statistical precision associated with certain pollutant sampling schedules led to comparison of two sampling schemes, designated as “modified random” and “systematic” sampling methods. A nearly uninterrupted body of data representing six years of sampling provided a basis from which to perform hypothetical “sampling” by the two methods. Comparison of results shows that the systematic method generally gave better results. The method is very simple; ft entails the selection of a sampling interval (other than 7 days or multiple of 7), the selection (randomly) of an initial sampling date, and regular sampling at the selected interval thereafter.     

Reference criteria for the identification of accident scenarios in the framework of land use planning

Land use planning (LUP) around industrial sites at risk of major accidents requires the application of sound approaches in the selection of credible accident scenarios. In fact, the ‘technical’ phase of LUP is based on the identification and assessment of relevant accident scenarios. An improper choice of scenarios may critically affect both the ‘technical’ phase of risk assessment and the following ‘policy’ phase concerning decision making on land-use restrictions and/or licensing. The present study introduces a procedure aimed at the systematic identification of reference accident scenarios to be used in the gathering of technical data on potential major accidents, which is a necessary step for LUP around Seveso sites. Possible accident scenarios are generated by an improved version of the MIMAH methodology (Methodology for the Identification of Major Accident Hazards). The accident scenarios are then assessed for LUP relevance considering severity, frequency and time scale criteria. The influence of prevention and mitigation barriers is also taken into account. Two applications are used to demonstrate the proposed procedure. In both case-studies, the proposed methodology proved successful in producing consistent sets of reference scenarios.