ABSTRACT Spatial analyses involving binning often require that every bin have the same area, but this is impossible using a rectangular grid laid over the Earth or over any projection of the Earth. Discrete global grids use hexagons, triangles, and diamonds to overcome this issue, overlaying the Earth with equally-sized bins. Such discrete global grids are formed by tiling the faces of a polyhedron. Previously, the orientations of these polyhedra have been chosen to satisfy only simple criteria such as equatorial symmetry or minimizing the number of vertices intersecting landmasses. However, projection distortion and singularities in discrete global grids mean that such simple orientations may not be sufficient for all use cases. Here, I present an algorithm for finding suitable orientations; this involves solving a nonconvex optimization problem. As a side-effect of this study I show that Fuller's Dymaxion map corresponds closely to one of the optimal orientations I find. I also give new high-accuracy calculations of the Poles of Inaccessibility, which show that Point Nemo, the Oceanic Pole of Inaccessibility, is 15?km farther from land than previously recognized. 相似文献
Governmental climate change mitigation targets are typically developed with the aid of forecasts of greenhouse-gas (GHG) emissions. The robustness and credibility of such forecasts depends, among other issues, on the extent to which forecasting approaches can reflect prevailing uncertainties. We apply a transparent and replicable method to quantify the uncertainty associated with projections of gross domestic product growth rates for Mexico, a key driver of GHG emissions in the country. We use those projections to produce probabilistic forecasts of GHG emissions for Mexico. We contrast our probabilistic forecasts with Mexico’s governmental deterministic forecasts. We show that, because they fail to reflect such key uncertainty, deterministic forecasts are ill-suited for use in target-setting processes. We argue that (i) guidelines should be agreed upon, to ensure that governmental forecasts meet certain minimum transparency and quality standards, and (ii) governments should be held accountable for the appropriateness of the forecasting approach applied to prepare governmental forecasts, especially when those forecasts are used to derive climate change mitigation targets.
POLICY INSIGHTS
No minimum transparency and quality standards exist to guide the development of GHG emission scenario forecasts, not even when these forecasts are used to set national climate change mitigation targets.
No accountability mechanisms appear to be in place at the national level to ensure that national governments rely on scientifically sound processes to develop GHG emission scenarios.
Using probabilistic forecasts to underpin emission reduction targets represents a scientifically sound option for reflecting in the target the uncertainty to which those forecasts are subject, thus increasing the validity of the target.
Setting up minimum transparency and quality standards, and holding governments accountable for their choice of forecasting methods could lead to more robust emission reduction targets nationally and, by extension, internationally.
Volcanoes of the Mariana arc system produce magmas that belong to several liquid lines of descent and that originated from several different primary magmas. Despite differences in parental magmas, phenocryst assemblages are very similar throughout the arc. The different liquid lines of descent are attributed to differences in degree of silica saturation of the primary liquids and in the processes of magmatic evolution (fractional crystallization vs magma mixing). Pseudoternary projections of volcanic rocks from several arc volcanoes are used to show differences between different magmatic suites. In most of the arc, parental liquids were Ol- and Hy-normative basalts that crystallized olivine, augite, and plagioclase (± iron-titanium oxide) and then plagioclase and two pyroxenes, apparently at low pressure. Eruptive rocks follow subparallel liquid lines of descent on element–element diagrams and on pseudoternary projections. Magmas at North Hiyoshi are Ne-normative and have a liquid line of descent along the thermal divide due to precipitation of olivine, augite, and plagioclase. Derived liquids are large ion lithophile element (LILE)-rich. Magmas at other Hiyoshi seamounts included an alkaline component but had more complex evolution. Those at Central Hiyoshi formed by a process dominated by mixing alkaline and subalkaline magmas, whereas those at other Hiyoshi seamounts evolved by combined magma mixing and fractional crystallization. Influence of the alkaline component wanes as one goes south from North Hiyoshi. Alkaline and subalkaline magmas were also mixed to produce magmas erupted at the Kasuga seamounts that are behind the arc front. The alkaline magmas at both Hiyoshi and Kasuga seamounts had different sources from those of the subalkaline magmas at those sites as indicated by trace element ratios and by Nd. 相似文献
ABSTRACTMap projections are given by forward transformation equations. Inverse transformation is derived from forward transformation analytically or numerically. In this paper, a numerical approach for inverse transformation of map projections is proposed, which is based on numerical differentiation and Newton–Raphson root finding method. This approach can facilitate the program developments for map projections when inverse transformation is needed. Numerical differentiation is tested with three map projections. It is seen that seven-digit precision or more can be reached. Boundary conditions and initial guess problem in inverse transformation are discussed. In terms of initial guess, map projections are divided into three categories, and appropriate initial guess values for cylindrical, pseudocylindrical, azimuthal, and conical projections in normal aspect are suggested. Newton–Raphson method with numerical differentiation is tested with 20 different map projections by using test data sets. The results show that the proposed approach is applicable if appropriate initial guess is available. 相似文献
Two approaches can be distinguished in studies of climate change impacts on water resources when accounting for issues related to impact model performance: (1) using a multi-model ensemble disregarding model performance, and (2) using models after their evaluation and considering model performance. We discuss the implications of both approaches in terms of credibility of simulated hydrological indicators for climate change adaptation. For that, we discuss and confirm the hypothesis that a good performance of hydrological models in the historical period increases confidence in projected impacts under climate change, and decreases uncertainty of projections related to hydrological models. Based on this, we find the second approach more trustworthy and recommend using it for impact assessment, especially if results are intended to support adaptation strategies. Guidelines for evaluation of global- and basin-scale models in the historical period, as well as criteria for model rejection from an ensemble as an outlier, are also suggested. 相似文献
Climate change may affect ocean and ice conditions in coastal oceans and thus have significant impacts on coastal infrastructure, marine navigation, and marine ecosystems. In this study a three-dimensional ice–ocean model is developed to examine likely changes of ocean and ice conditions over the Newfoundland and Labrador Shelves in response to climate change. The model is configured with a horizontal grid of approximately 7?km and a vertical grid of 46 levels and is run from 1979 to 2069. The projection period is 2011 to 2069 under a median emission scenario A1B used by the Intergovernmental Panel on Climate Change. For the projection period, the surface atmospheric forcing fields used are from the Canadian Regional Climate Model over the North Atlantic. The open boundary conditions come from the Canadian Global Climate Model, Version 3 (CGCM3), adjusted for the 1981–2010 mean of the Simple Ocean Data Assimilation model output. The simulated fields over the 1981–2010 period have patterns consistent with observations. Over the Newfoundland and Labrador Shelves during the projection period, the model shows general trends of warming, freshening, and decreasing ice. From 2011 to 2069, the model projects that under A1B sea surface temperature will increase by 1.4°C; bottom temperature will increase by 1.6°C; sea surface salinity will decrease by 0.7; bottom salinity will decrease by 0.3; and sea-ice extent will decrease by 70%. The sea level will rise by 0.11?m at the St. John's tide-gauge station because of oceanographic change, and the freshwater transport of the Labrador Current will double as a result of freshening. The regional ice–ocean model reproduces more realistic present climate conditions and projects considerably different future climate conditions than CGCM3. 相似文献