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A. Gabàs A. Macau B. Benjumea F. Bellmunt S. Figueras M. Vilà 《Surveys in Geophysics》2014,35(4):983-1002
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Climate model ensembles are used to estimate uncertainty in future projections, typically by interpreting the ensemble distribution for a particular variable probabilistically. There are, however, different ways to produce climate model ensembles that yield different results, and therefore different probabilities for a future change in a variable. Perhaps equally importantly, there are different approaches to interpreting the ensemble distribution that lead to different conclusions. Here we use a reduced-resolution climate system model to compare three common ways to generate ensembles: initial conditions perturbation, physical parameter perturbation, and structural changes. Despite these three approaches conceptually representing very different categories of uncertainty within a modelling system, when comparing simulations to observations of surface air temperature they can be very difficult to separate. Using the twentieth century CMIP5 ensemble for comparison, we show that initial conditions ensembles, in theory representing internal variability, significantly underestimate observed variance. Structural ensembles, perhaps less surprisingly, exhibit over-dispersion in simulated variance. We argue that future climate model ensembles may need to include parameter or structural perturbation members in addition to perturbed initial conditions members to ensure that they sample uncertainty due to internal variability more completely. We note that where ensembles are over- or under-dispersive, such as for the CMIP5 ensemble, estimates of uncertainty need to be treated with care. 相似文献
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Global and regional coupled climate sensitivity to the parameterization of rainfall interception 总被引：1，自引：0，他引：1
Jiafu Mao Andrew J. Pitman Steven J. Phipps Gab Abramowitz YingPing Wang 《Climate Dynamics》2011,37(1-2):171-186
A coupled land?Catmosphere model is used to explore the impact of seven commonly used canopy rainfall interception schemes on the simulated climate. Multiple 30-year simulations are conducted for each of the seven methods and results are analyzed in terms of the mean climatology and the probability density functions (PDFs) of key variables based on daily data. Results show that the method used for canopy interception strongly affects how rainfall is partitioned between canopy evaporation and throughfall. However, the impact on total evaporation is much smaller, and the impact on rainfall and air temperature is negligible. Similarly, the PDFs of canopy evaporation and transpiration for six selected regions are strongly affected by the method used for canopy interception, but the impact on total evaporation, temperature and precipitation is negligible. Our results show that the parameterization of rainfall interception is important to the surface hydrometeorology, but the seven interception parameterizations examined here do not cause a statistically significant impact on the climate of the coupled model. We suggest that broad scale climatological differences between coupled climate models are not likely the result of how interception is parameterized. This conclusion is inconsistent with inferences derived from earlier uncoupled simulations, or simulations using very simplified climate models. 相似文献
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Natural Hazards - This paper examines methods for quantitatively identifying communities that have high social vulnerability to environmental hazards. We first provide an overview of the existing... 相似文献
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A. Gabàs A. Macau B. Benjumea P. Queralt J. Ledo S. Figueras A. Marcuello 《Surveys in Geophysics》2016,37(5):897-921
The structure of Cerdanya Basin (north-east of Iberian Peninsula) is partly known from geological cross sections, geological maps and vintage geophysical data. However, these data do not have the necessary resolution to characterize some parts of Cerdanya Basin such as the thickness of soft soil, geometry of bedrock or geometry of geological units and associated faults. For all these reasons, the main objective of this work is to improve this deficiency carrying out a detailed study in this Neogene basin applying jointly the combination of passive seismic methods (H/V spectral ratio and seismic array) and electromagnetic methods (audio-magnetotelluric and magnetotelluric method). The passive seismic techniques provide valuable information of geometry of basement along the profile. The maximum depth is located near Alp village with a bedrock depth of 500 m. The bedrock is located in surface at both sites of profile. The Neogene sediments present a shear-wave velocity between 400 and 1000 m/s, and the bedrock basement presents a shear-wave velocity values between 1700 and 2200 m/s. These results are used as a priori information to create a 2D resistivity initial model which constraints the inversion process of electromagnetic data. We have obtained a 2D resistivity model which is characterized by (1) a heterogeneous conductivity zone (<40 Ohm m) that corresponds to shallow part of the model up to 500 m depth in the centre of the profile. These values have been associated with Quaternary and Neogene sediments formed by silts, clays, conglomerates, sandstones and gravels, and (2) a deeper resistive zone (1000–3000 Ohm m) interpreted as Palaeozoic basement (sandstones, limestones and slates at NW and conglomerates and microconglomerates at SE). The resistive zone is truncated by a discontinuity at the south-east of the profile which is interpreted as the Alp-La Tet Fault. This discontinuity is represented by a more conductive zone (600 Ohm m approx.) and is explained as a combination of fractured rock and a fluid network. The result highlights that the support between different geophysical methods is essential in producing geophysical meaningful models. 相似文献
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Stable isotope and trace element contents of Cyprideis torosa valves from the Lower Pleistocene marginal lacustrine sequence of Barranco León, Baza Basin (Southern Spain), allow us to
reconstruct the geochemical record of environmental change in this marginal area of the basin and to compare these data with
the environmental changes inferred from the faunal associations. Hydrochemical features of the Baza Lake system have been
influenced by changes in water source, solute composition, and water level during the past. Three water types may have been
involved in a complex mixing in the marginal area during the studied intervals (1) waters of the Baza lacustrine system that
underwent large P/E changes, (2) dilute, meteoric water inputs (surface and shallow groundwaters), (3) saline groundwater
inputs of meteoric origin that acquired their salinity by halite and gypsum dissolution. Four stages in the Pleistocene paleoenvironmental
evolution of the Barranco León area have been differentiated: stage I records a high lake level (highstand) of the saline
closed-lake system. Stage II corresponds to very shallow, palustrine conditions. Stage III records the varying influence of
the three water types under changing water level in a closed-lake. Stage IV corresponds to a through-flowing, open lacustrine
environment mainly fed by meteoric saline groundwaters with minor inputs of stream waters. This small through-flowing lake
was connected to a larger, inner saline closed-lake system. The BL 5 mammal site with lithic tools of an early human occupation
phase in Western Europe corresponds to a particular episode within this stage of the environmental evolution in the marginal
zone of the Baza Lake.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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Climate model dependence and the replicate Earth paradigm 总被引：1，自引：1，他引：0
Multi-model ensembles are commonly used in climate prediction to create a set of independent estimates, and so better gauge the likelihood of particular outcomes and better quantify prediction uncertainty. Yet researchers share literature, datasets and model code—to what extent do different simulations constitute independent estimates? What is the relationship between model performance and independence? We show that error correlation provides a natural empirical basis for defining model dependence and derive a weighting strategy that accounts for dependence in experiments where the multi-model mean would otherwise be used. We introduce the “replicate Earth” ensemble interpretation framework, based on theoretically derived statistical relationships between ensembles of perfect models (replicate Earths) and observations. We transform an ensemble of (imperfect) climate projections into an ensemble whose mean and variance have the same statistical relationship to observations as an ensemble of replicate Earths. The approach can be used with multi-model ensembles that have varying numbers of simulations from different models, accounting for model dependence. We use HadCRUT3 data and the CMIP3 models to show that in out of sample tests, the transformed ensemble has an ensemble mean with significantly lower error and much flatter rank frequency histograms than the original ensemble. 相似文献
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