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1.
A comparison of full-field and anomaly initialization for seasonal to decadal climate prediction 总被引:1,自引:1,他引:0
There are two main approaches for dealing with model biases in forecasts made with initialized climate models. In full-field initialization, model biases are removed during the assimilation process by constraining the model to be close to observations. Forecasts drift back towards the model’s preferred state, thereby re-establishing biases which are then removed with an a posterior lead-time dependent correction diagnosed from a set of historical tests (hindcasts). In anomaly initialization, the model is constrained by observed anomalies and deviates from its preferred climatology only by the observed variability. In theory, the forecasts do not drift, and biases may be removed based on the difference between observations and independent model simulations of a given period. Both approaches are currently in use, but their relative merits are unclear. Here we compare the skill of each approach in comprehensive decadal hindcasts starting each year from 1960 to 2009, made using the Met Office decadal prediction system. Both approaches are more skilful than climatology in most regions for temperature and some regions for precipitation. On seasonal timescales, full-field initialized hindcasts of regional temperature and precipitation are significantly more skilful on average than anomaly initialized hindcasts. Teleconnections associated with the El Niño Southern Oscillation are stronger with the full-field approach, providing a physical basis for the improved precipitation skill. Differences in skill on multi-year timescales are generally not significant. However, anomaly initialization provides a better estimate of forecast skill from a limited hindcast set. 相似文献
2.
Gabriel Grigorescu Paul Alexander Rosie C. Bolton Roshene McCool 《Experimental Astronomy》2009,27(1-2):95-107
The future Square Kilometre Array (SKA) radio telescope is an interferometer array that will use a variety of collector types, including approximately 2500 dishes distributed with separations up to a few thousand kilometres, and about 250 aperture array (AA) stations located within 200 km of the core. The data rates associated with each individual collector are vast: around 10 GBytes/s for each dish and 2 TBytes/s for an AA station. As each of these must be connected directly to a central correlator, designing a cost-effective cabling and trenching infrastructure presents a great engineering challenge. In this paper we discuss approaches to performing this optimisation. In graph theory, the concept of a minimum spanning tree (MST) is equivalent to finding the minimum total trench length joining a set of n arbitrary points in the plane. We have developed a set of algorithms which optimise the infrastructure of any given telescope layout iteratively, taking into consideration not only trenching but also cabling and jointing costs as well. Solutions for few example configurations of telescope layout are presented. We have found that these solutions depend significantly on the collectors’ output data rates. When compared to a “traditional” MST-based approach which minimises trenching costs only, our algorithms can further reduce total costs by up to 15–20%. This can influence greatly the SKA infrastructure related costs. 相似文献
3.
Matthew J. Genge Luke Alesbrook Natasha V. Almeida Helena C. Bates Phil A. Bland Mark R. Boyd Mark J. Burchell Gareth S. Collins Luke T. Cornwell Luke Daly Hadrien A. R. Devillepoix Matthias van Ginneken Ansgar Greshake Daniel Hallatt Christopher Hamann Lutz Hecht Laura E. Jenkins Diane Johnson Rosie Jones Ashley J. King Haithem Mansour Sarah McMullan Jennifer T. Mitchell Gavyn Rollinson Sara S. Russell Christian Schröder Natasha R. Stephen Martin D. Suttle Jon D. Tandy Patrick Trimby Eleanor K. Sansom Vassilia Spathis Francesca M. Willcocks Penelope J. Wozniakiewicz 《Meteoritics & planetary science》2024,59(5):948-972
Fusion crusts form during the atmospheric entry heating of meteorites and preserve a record of the conditions that occurred during deceleration in the atmosphere. The fusion crust of the Winchcombe meteorite closely resembles that of other stony meteorites, and in particular CM2 chondrites, since it is dominated by olivine phenocrysts set in a glassy mesostasis with magnetite, and is highly vesicular. Dehydration cracks are unusually abundant in Winchcombe. Failure of this weak layer is an additional ablation mechanism to produce large numbers of particles during deceleration, consistent with the observation of pulses of plasma in videos of the Winchcombe fireball. Calving events might provide an observable phenomenon related to meteorites that are particularly susceptible to dehydration. Oscillatory zoning is observed within olivine phenocrysts in the fusion crust, in contrast to other meteorites, perhaps owing to temperature fluctuations resulting from calving events. Magnetite monolayers are found in the crust, and have also not been previously reported, and form discontinuous strata. These features grade into magnetite rims formed on the external surface of the crust and suggest the trapping of surface magnetite by collapse of melt. Magnetite monolayers may be a feature of meteorites that undergo significant degassing. Silicate warts with dendritic textures were observed and are suggested to be droplets ablated from another stone in the shower. They, therefore, represent the first evidence for intershower transfer of ablation materials and are consistent with the other evidence in the Winchcombe meteorite for unusually intense gas loss and ablation, despite its low entry velocity. 相似文献
4.
The sea surface temperature anomalies(SSTAs) in the tropical Indian Ocean(TIO) show two dominant modes at interannual time scales,referred to as the Indian Ocean basin mode(IOBM) and dipole mode(IOD).Recent studies have shown that the IOBM and IOD not only affect the local climate,but also induce remarkable influences in East Asia via teleconnections.In this study,we assess simulations of the IOBM and IOD,as well as their teleconnections,using the operational seasonal prediction models from the Met Office(Had GEM3) and Beijing Climate Center [BCC CSM1.1(m)].It is demonstrated that the spatial patterns and seasonal cycles are generally reproduced by the control simulations of BCC CSM1.1(m) and Had GEM3,although spectra biases exist.The relationship between the TIO SSTA and El Nio is successfully simulated by both models,including the persistent IOBM warming following El Nio and the IOD–El Nio interactions.BCC CSM1.1(m) and Had GEM3 are capable of simulating the observed local impact of the IOBM,such as the strengthening of the South Asian high.The influences of the IOBM on Yangtze River rainfall are also captured well by both models,although this teleconnection is slightly weaker in BCC CSM1.1(m) due to the underestimation of the northwestern Pacific subtropical high.The local effect of the IOD on East African rainfall is reproduced by both models.However,the remote control of the IOD on rainfall over southwestern China is not clear in either model.It is shown that the realistic simulations of TIO SST modes and their teleconnections give rise to the source of skillful seasonal predictions over China. 相似文献
5.
The divergent city: unequal and uneven development in St. Louis 总被引:1,自引:1,他引:0
In St. Louis, as in many other cities, decline and displacement occurred when key policies, prejudices, and plans interacted with broad economic restructuring to devastate poor and minority communities, while leaving White and middle-class communities largely intact. Amidst overall population loss and neighborhood decline are pockets of prosperity and gentrification within the central city. In this article, we analyze three significant planning interventions in St. Louis, Missouri, that spurred displacement of populations—urban renewal, triage, and the foreclosure crisis. We argue that the differential experiences of Black and White during each of these periods represent two faces of development: one in the north of the city that is largely Black, experiencing vacant land, high crime, and crumbling infrastructure; another in the south of the city that is largely White, enjoying pockets of vibrant commercial development, larger homes, and stable real estate markets. We analyze each period through a framework of uneven and unequal development and displacement, which we call the Divergent City Theory. Based on this theory, planners face an ethical obligation to plan for the future of their cities in a way that seeks to reconcile the structured race and class inequalities of the divergent city. 相似文献
6.
Ultra‐large rift basins, which may represent palaeo‐propagating rift tips ahead of continental rupture, provide an opportunity to study the processes that cause continental lithosphere thinning and rupture at an intermediate stage. One such rift basin is the Faroe‐Shetland Basin (FSB) on the north‐east Atlantic margin. To determine the mode and timing of thinning of the FSB, we have quantified apparent upper crustal β‐factors (stretching factors) from fault heaves and apparent whole‐lithosphere β‐factors by flexural backstripping and decompaction. These observations are compared with models of rift basin formation to determine the mode and timing of thinning of the FSB. We find that the Late Jurassic to Late Palaeocene (pre‐Atlantic) history of the FSB can be explained by a Jurassic to Cretaceous depth‐uniform lithosphere thinning event with a β‐factor of ~1.3 followed by a Late Palaeocene transient regional uplift of 450–550 m. However, post‐Palaeocene subsidence in the FSB of more than 1.9 km indicates that a Palaeocene rift with a β‐factor of more than 1.4 occurred, but there is only minor Palaeocene or post‐Palaeocene faulting (upper crustal β‐factors of less than 1.1). The subsidence is too localized within the FSB to be caused by a regional mantle anomaly. To resolve the β‐factor discrepancy, we propose that the lithospheric mantle and lower crust experienced a greater degree of thinning than the upper crust. Syn‐breakup volcanism within the FSB suggests that depth‐dependent thinning was synchronous with continental breakup at the adjacent Faroes and Møre margins. We suggest that depth‐dependent continental lithospheric thinning can result from small‐scale convection that thins the lithosphere along multiple offset axes prior to continental rupture, leaving a failed breakup basin once seafloor spreading begins. This study provides insight into the structure and formation of a generic global class of ultra‐large rift basins formed by failed continental breakup. 相似文献
7.
Laura Venn Moya Kneafsey Lewis Holloway Rosie Cox Elizabeth Dowler Helena Tuomainen 《Area》2006,38(3):248-258
Recent European literature on 'alternative' food networks (AFNs) draws heavily upon an apparently accessible and diverse body of non-conventional food networks in the agro-food sector and whilst researchers frequently refer to individual examples of farmers markets, box schemes, producer cooperatives and community-supported agriculture projects, less attention is given to the methodological processes that facilitate the identification and examination of these networks. From the preliminary stages of a research project focusing on examples of AFNs, 2 this paper examines the process of operationalizing AFNs research and reviews the difficulties associated with identifying, comparing and characterizing AFNs. 相似文献
8.
Rosie Chance Alex R. Baker Frithjof C. Küpper Claire Hughes Bernard Kloareg Gill Malin 《Estuarine, Coastal and Shelf Science》2009
A number of field and laboratory studies on the impact of marine macroalgae on dissolved inorganic iodine speciation are presented. Within tidally isolated rock pools, the brown macroalga Fucus serratus was found to both release stored iodide and to facilitate the reduction of iodate to iodide. In contrast, no discernible changes in iodine speciation were observed in rock pools containing green macroalgae of the genus Ulva. Incubation experiments confirmed that the macroalgae Laminaria digitata, F. serratus and Kallymenia antarctica release iodide, though the rate of release varied between species and between specimens of the same species. Application of oxidative stress by treatment with cell wall derived oligoguluronate elicitors increased the efflux of iodide by L. digitata approximately 20-fold. The release of iodide by macroalgae may impact upon the formation of volatile iodine species (molecular iodine and iodocarbons) that are of importance in the coastal atmosphere. 相似文献
9.
Interaction between a river and its wetland: evidence from the Murray River for spatial variability in diatom and radioisotope records 总被引:1,自引:1,他引:0
Sinclair Flat is small wetland, located within the gorge section of the Murray River floodplain. situated near Blanchetown,
South Australia, the wetland is closely linked to the River and, since regulation, has become permanently inundated. High
summer evaporation rates deplete the volume of water within the wetland. However, this is compensated by perennial inflow
via a permanent inlet from the River. This site provides an opportunity to explore the relative contribution of river and
wetland diatom flora to the sediment record, and the fluvial and aerial contribution of radiometric isotopes to the system.
The geochronological and biostratigraphic data provide an insight into the history of the water quality of Sinclair Flat.
Evidence exists for the River being a source of sediments and isotopes and of diatom species typical of the main river channel.
Prior to 1950, Sinclair Flat was an oligotrophic, oligosaline, clear-water wetland. The wetland shifted gradually to an environment
that favoured clear-water benthic species, most likely as a consequence of changes following river regulation in the 1920s,
although the capacity to date these sediments is limited. During the 1950s, the wetland became plankton dominated. Peaks in
epiphytic diatoms during the 1960s suggest increased emergent macrophyte cover. The contemporary condition is of a connected,
turbid, eutrophic and mesosaline lagoon. The ecological condition of Sinclair Flat has diverged considerably from its historical
range of condition. This record supports evidence from upstream of widespread state switches in the Murray–Darling Basin floodplain
wetlands. This record also lends considerable weight to modern studies attesting to the degraded state of the waterways of
the Murray–Darling Basin and the impact of river regulation practices on the water quality of these ecosystems. 相似文献
10.
LaForce Tara Ebeida Mohamed Jordan Spencer Miller Terry A. Stauffer Philip H. Park Heeho Leone Rosie Hammond Glenn 《Mathematical Geosciences》2023,55(2):129-161
Mathematical Geosciences - Mesh generation lies at the interface of geological modeling and reservoir simulation. Highly skewed or very small grid cells may be necessary to accurately capture the... 相似文献