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1.
Climate change is likely to manifest in river flow changes across the globe, which could have wide-ranging consequences for society and the natural environment. A number of previous studies used the UK Climate Projections 2009 (UKCP09) to investigate the potential impacts on river flows in Britain, but these projections were recently updated by the release of UKCP18, thus there is a need to update flow studies. Here, the UKCP18 Regional (12 km) projections are applied using a national-scale grid-based hydrological model, to investigate potential future changes in seasonal mean river flows across Great Britain. Analysis of hydrological model performance using baseline climate model data (1980–2010) shows relatively good agreement with use of observation-based data, particularly after application of a monthly precipitation bias-correction. Analysis of seasonal mean flow changes for two future time-slices (2020–2050 and 2050–2080) suggests large decreases in summer flows across the country (median −45% by 2050–2080), but possible increases in winter flows (median 9% by 2050–2080), especially in the north and west. Information on the potential range of flow changes using the latest projections is necessary to develop appropriate adaptation strategies, and comparisons with previous projections can help update existing plans, although such comparisons are often not straightforward.  相似文献   
2.
The 2018 typhoon season in the western North Pacific(WNP) was highly active, with 26 named tropical cyclones(TCs) from June to November, which exceeded the climatological mean(22) and was the second busiest season over the past twenty years. More TCs formed in the eastern region of the WNP and the northern region of the South China Sea(SCS). More TCs took the northeast quadrant in the WNP, recurving from northwestward to northward and causing heavy damages in China's Mainland(69.73 billion yuan) in 2018. Multiscale climate variability is conducive to an active season via an enhanced monsoon trough and a weakened subtropical high in the WNP. The large-scale backgrounds in 2018 showed a favorable environment for TCs established by a developing central Pacific(CP) El Ni?o and positive Pacific meridional mode(PMM)episode on interannual timescales. The tropical central Pacific(TCP) SST forcing exhibits primary control on TCs in the WNP and large-scale circulations, which are insensitive to the PMM. During CP El Ni?o years, anomalous convection associated with the TCP warming leads to significantly increased anomalous cyclonic circulation in the WNP because of a Gill-type Rossby wave response. As a result, the weakened subtropical high and enhanced monsoon trough shift eastward and northward, which favor TC genesis and development. Although such increased TC activity in 2018 might be slightly suppressed by interdecadal climate variability, it was mostly attributed to the favorable interannual background. In addition, high-frequency climate signals,such as intraseasonal oscillations(ISOs) and synoptic-scale disturbances(SSDs), interacted with the enhanced monsoon trough and strongly modulated regional TC genesis and development in 2018.  相似文献   
3.
Although electron probe microanalysis and secondary ion mass spectrometry are widely used analytical techniques for geochemical and mineralogical applications, metrologically rigorous quantification remains a major challenge for these methods. Secondary ion mass spectrometry (SIMS) in particular is a matrix‐sensitive method, and the use of matrix‐matched reference materials (RMs) is essential to avoid significant analytical bias. A major problem is that the number of available RMs for SIMS is extremely small compared with the needs of analysts. One approach for the production of matrix‐specific RMs is the use of high‐energy ion implantation that introduces a known amount of a selected isotope into a material. We chose the more elaborate way of implanting a so‐called ‘box‐profile’ to generate a quasi‐homogeneous concentration of the implanted isotope in three dimensions, which allows RMs not only to be used for ion beam analysis but also makes them suitable for EPMA. For proof of concept, we used the thoroughly studied mineralogically and chemically ‘simple’ SiO2 system. We implanted either 47Ti or 48Ti into synthetic, ultra‐high‐purity silica glass. Several ‘box‐profiles’ with mass fractions between 10 and 1000 μg g?1 Ti and maximum depths of homogeneous Ti distribution between 200 nm and 3 μm were produced at the Institute of Ion Beam Physics and Materials Research of Helmholtz‐Zentrum Dresden‐Rossendorf. Multiple implantation steps using varying ion energies and ion doses were simulated with Stopping and Range of Ions in Matter (SRIM) software, optimising for the target concentrations, implantation depths and technical limits of the implanter. We characterised several implant test samples having different concentrations and maximum implantation depths by means of SIMS and other analytical techniques. The results show that the implant samples are suitable for use as reference materials for SIMS measurements. The multi‐energy ion implantation technique also appears to be a promising procedure for the production of EPMA‐suitable reference materials.  相似文献   
4.
缪阿丽  李锋  王俊  祝涛  叶碧文 《地震》2021,41(4):192-202
2018年4月6日无为ML4.1地震前的地下流体前兆异常特征以及该地震的震源机制解进行了分析, 结果表明, 无为地震前的异常分布在距震中64~233 km范围内, 这些异常在时间进程上, 可分为中期趋势背景异常和短临异常, 主要以中期趋势背景异常为主。 这些中期趋势背景异常均表现为水位的破年变变化。 从空间演化上看, 2018年安徽无为ML4.1地震前出现的中期趋势背景异常沿着长江破碎带有序分布。 这种比较明显的异常群体性特征为地震预测提供了较好的依据。 震源机制解结果显示, 节面I的走向为NE向, 节面Ⅱ的走向NW向。 反演的震源机制的P轴(主压轴)方向为NE向(70°), 倾角近水平(7°)。 无为地震震源机制解所得主压应力作用方向与无为地震前异常展布方向相同。 这说明地震孕育过程中区域应力加载作用和流体前兆响应具有密切关系。  相似文献   
5.
Experimentally determined spatial patterns of soil redistribution across a break in slope derived using 10 rare earth element (REE) oxides as sediment tracers are presented. An erosion experiment was conducted using simulated rainfall within a laboratory slope model measuring 2·5 m wide by 6 m long with a gradient of 15° declining to 2°. Soil was tagged with multiple REE and placed in different locations over the slope and at the end of the experiment REE concentrations were measured in samples collected spatially. A new method was developed to quantify the erosion and deposition depths spatially, the relative source contributions to deposited sediment and the sediment transport distances. Particle‐size selectivity over an area of net deposition was also investigated, by combining downslope changes in particle‐size distributions with changes in sediment REE composition within a flow pathway. During the experiment, the surface morphology evolved through upslope propagation of rill headcuts, which gradually incised the different REE‐tagged zones and led to sediment deposition at the break in slope and the development of a fan extending over the shallow slope segment. The spatial patterns in REE concentrations, the derived erosion and deposition depths, the relative source contributions to deposition zones and the sediment transport distances, corroborate the morphological observations and demonstrate the potential of using REE for quantifying sediment transport processes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
6.
Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north‐western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the ‘Sidestrand Unio‐bed’, here defined as the Sidestrand Hall Member of the Cromer Forest‐bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio‐bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomys savini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the ‘Cromerian Complex’ and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial – probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the ‘new glacial stratigraphy’ during MIS 16, 12, 10 and 6. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
7.
When viewed from the air, Scottish ‘hummocky moraine’ can be resolved into a series of linear ridges that resemble those found at the margins of actively retreating glaciers today. Recent work has supported the interpretation of these linear ridges as ice-marginal landforms and the authors believe that the majority of ‘hummocky moraine’ deposits can be interpreted in this way. Consequently the pattern of deglaciation can be established fairly precisely from the pattern of linear ridges. This approach is applied to the landforms of the northern part of the Loch Lomond Stadial ice-field in order to reconstruct the regional pattern of deglaciation. This leads to important inferences about the significance of topographic control during deglaciation and more importantly it provides fresh insight into the environment of the British Isles during the Loch Lomond Stadial.  相似文献   
8.
Moss and grass remains associated with a well-developed in situ palaeosol buried beneath a moraine ridge in front of Nigardsbreen (Jostedalsbreen ice cap, southern Norway) have been 14C-dated. Pollen preserved with the plant remains suggests the existence of an agricultural landscape prior to the deposition of the moraine. The calibrated dates and the pollen spectra are in close accord with historically-documented evidence for the timing and palaeoenvironment of the ‘Little Ice Age’ advance of the glacier. Considerable potential is indicated for estimating the maximum ages of moraine ridges and for palaeoenvironmental reconstruction where such documentary evidence does not exist.  相似文献   
9.
This paper is about conditions and processes during the accumulation of the Upper Pleniglacial Middle and Upper Silt Loam complexes at Nagelbeek, Limbourg, a Weichselian stratigraphical type locality. The complexes correlate with Hesbayan and Brabantian loesses in Belgium, formed between 28,000 and 12,400 yrs BP. They are characterized by sediment features (cracks, mass deformations, and cut-and-fill features) that are ascribed to a cryogenic regimen. The main Middle Silt Loam subunit contains contraction cracks deformed and further modified by masswasting. Intra-Upper-Pleniglacial pedogenic intervals are inferred from three greyish bands, from a truncated weathered zone surmounting the Middle Silt Loam, and from an aeolian-cumulic palaeosol at the base of the Upper Silt Loam. Latter two zones and an intervening erosional unconformity were cryogenically reworked, less than 22,000 yrs BP, to form a complex stratigraphical marker-zone: the ‘Horizon à Langues de Nagelbeek’. Morphological variants of the marker-zone are described. The geomorphic evolution of the Nagelbeek upland, from Saalian to Holocene times, is summarized in unconformity maps and a time diagram.  相似文献   
10.
In the traditional incremental analysis update(IAU) process, all analysis increments are treated as constant forcing in a model’s prognostic equations over a certain time window. This approach effectively reduces high-frequency oscillations introduced by data assimilation. However, as different scales of increments have unique evolutionary speeds and life histories in a numerical model, the traditional IAU scheme cannot fully meet the requirements of short-term forecasting for the damping of hig...  相似文献   
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