Heliophysics Event Knowledgebase for?the?Solar Dynamics Observatory (SDO) and Beyond     

N. Hurlburt  M. Cheung  C. Schrijver  L. Chang  S. Freeland  S. Green  C. Heck  A. Jaffey  A. Kobashi  D. Schiff  J. Serafin  R. Seguin  G. Slater  A. Somani  R. Timmons 《Solar physics》2012,275(1-2):67-78

The immense volume of data generated by the suite of instruments on the Solar Dynamics Observatory (SDO) requires new tools for efficient identifying and accessing data that is most relevant for research. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The HEK system combines automated data mining using feature-detection methods and high-performance visualization systems for data markup. In addition, web services and clients are provided for searching the resulting metadata, reviewing results, and efficiently accessing the data. We review these components and present examples of their use with SDO data.  相似文献   

To what extent have changes in channel capacity contributed to flood hazard trends in England and Wales?          下载免费PDF全文

Louise J. Slater 《地球表面变化过程与地形》2016,41(8):1115-1128

The frequency of floods has been projected to increase across Europe in the coming decades due to extreme weather events. However, our understanding of how flood frequency is affected by geomorphic changes in river channel capacity remains limited. This paper seeks to quantify the influence of trends in channel capacity on flood hazards. Measuring and predicting the effect of geomorphic changes on freshwater flooding is essential to mitigate the potential effects of major floods through informed planning and response. Hydrometric records from 41 stream gauging stations were used to measure trends in the flood stage (i.e. water surface elevation) frequency above the 1% annual exceedance threshold. The hydrologic and geomorphic components of flood hazard were quantified separately to determine their contribution to the total trend in flood stage frequency. Trends in cross‐sectional flow area and mean flow velocity were also investigated at the same flood stage threshold. Results showed that a 10% decrease (or increase) in the channel capacity would result in an increase (or decrease) in the flood frequency of approximately 1.5 days per year on average across these 41 sites. Widespread increases in the flood hazard frequency were amplified through both hydrologic and geomorphic effects. These findings suggest that overlooking the potential influence of changing channel capacity on flooding may be hazardous. Better understanding and quantifying the influence of geomorphic trends on flood hazard will provide key insight for managers and engineers into the driving mechanisms of fluvial flooding over relatively short timescales. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The effect of peat structure on the spatial distribution of biogenic gases within bogs          下载免费PDF全文

Xavier Comas  Nicholas Kettridge  Andrew Binley  Lee Slater  Andrew Parsekian  Andy J. Baird  Maria Strack  James M. Waddington 《水文研究》2014,28(22):5483-5494

Northern peatlands are a large source of atmospheric methane (CH₄) and both a source and a sink of atmospheric carbon dioxide (CO₂). The rate and temporal variability in gas exchanges with peat soils is directly related to the spatial distribution of these free‐phase gases within the peat column. In this paper, we present results from surface and borehole ground‐penetrating radar surveys – constrained with direct soil and gas sampling – that compare the spatial distribution of gas accumulations in two raised bogs: one in Wales (UK), the other in Maine (USA). Although the two peatlands have similar average thickness, physical properties of the peat matrix differ, particularly in terms of peat type and degree of humification. We hypothesize that these variations in physical properties are responsible for the differences in gas distribution between the two peatlands characterized by (1) gas content up to 10.8% associated with woody peat and presence of wood layers in Caribou Bog (Maine) and (2) a more homogenous distribution with gas content up to 5.7% at the surface (i.e. <0.5 m deep) in Cors Fochno (Wales). Our results highlight the variability in biogenic gas accumulation and distribution across peatlands and suggest that the nature of the peat matrix has a key role in defining how biogenic gas accumulates within and is released to the atmosphere from peat soils. © 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.  相似文献   

SWRI/LASP Sounding Rocket Inter-Calibration With The Eit Instrument On Board SOHO     

Auchère  Frédéric  Hassler  Donald M.  Slater  David C.  Woods  Thomas N. 《Solar physics》2001,202(2):269-280

Two successful sounding rocket flights were launched on 15 May 1997 and 2 November 1998 with an objective of providing inter-calibration with several of the instruments on board SOHO and TRACE. We will discuss here the results of the inter-calibration between the SwRI/LASP rocket imaging instruments and the Extreme-ultraviolet Imaging Telescope (EIT) on SOHO. The Multiple XUV Imager (MXUVI) sounding rocket instrument is a multi-layer mirror telescope equipped with an internal occulter and light trap to provide full-disk images of Feix/x 17.1 nm and off-limb observations of Heii 30.4 nm. The SOHO/EIT instrument is also a full-disk multi-layer imager with four channels, Fe ix/x 17.1 nm, Fexii 19.5 nm, Fexv 28.4 nm and Heii 30.4 nm. By comparison with the EIT observations taken at the same time, we provide new flat-field determinations for EIT which help quantify the sensitivity degradation of the EIT detector, as well as provide a measure of the off-limb stray-light characteristics of the two instruments. We find that the EIT stray-light function is strongly asymmetric, with greater stray light in the 17.1 and 19.5 nm quadrants than the 30.4 and 28.4 nm quadrants. Two possible causes of this asymmetry are the polishing processes of the EIT mirrors and the asymmetric support grid pattern in the foil mesh at the EIT pupil.  相似文献   

Between a rock and a hard place: contested livelihoods in Qwaqwa National Park, South Africa     

Rachel Slater 《The Geographical journal》2002,168(2):116-129

This paper examines rural livelihoods and the prospects for participatory conservation through a case study of Qwaqwa National Park (QNP) in South Africa. The park was established in 1992 in the context of South Africa's transition to democracy, growing ecotourism in the country and global movements towards conservation involving and benefiting local people. The paper argues that the protracted conflict between park residents and management led to new patterns of livelihood activities and household formation, and resulted in material and social differentiation amongst park households. The goals of park management, with a commitment to nature conservation and ecotourism, were at odds with the livelihood practices of park residents. Conflicts arose over stocking levels, overgrazing, wood-cutting and deforestation and over the use of other natural resources, including water and medicinal plants. The park was the site of a Rand Water project that employed many residents. Residents found themselves between a rock and a hard place as they resisted attempts by the management to reduce stocking levels and yet relied on management to gain access to sources of paid employment.  相似文献   

Whitsuntide excursion to the Cromer and Norwich Districts: May 18th–23rd, 1923     

P.G.H. Boswell  G. Slater 《Proceedings of the Geologists' Association. Geologists' Association》1923,34(3):223-IN5

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Hydrological data assimilation with the ensemble Kalman filter: Use of streamflow observations to update states in a distributed hydrological model   总被引：1，自引：0，他引：1  

Martyn P. Clark  David E. Rupp  Ross A. Woods  Xiaogu Zheng  Richard P. Ibbitt  Andrew G. Slater  Jochen Schmidt  Michael J. Uddstrom 《Advances in water resources》2008

This paper describes an application of the ensemble Kalman filter (EnKF) in which streamflow observations are used to update states in a distributed hydrological model. We demonstrate that the standard implementation of the EnKF is inappropriate because of non-linear relationships between model states and observations. Transforming streamflow into log space before computing error covariances improves filter performance. We also demonstrate that model simulations improve when we use a variant of the EnKF that does not require perturbed observations. Our attempt to propagate information to neighbouring basins was unsuccessful, largely due to inadequacies in modelling the spatial variability of hydrological processes. New methods are needed to produce ensemble simulations that both reflect total model error and adequately simulate the spatial variability of hydrological states and fluxes.  相似文献   

Rosetta-Alice observations of exospheric hydrogen and oxygen on Mars     

Paul D. Feldman  Andrew J. Steffl  Michael F. A’Hearn  S. Alan Stern  David C. Slater  Henry B. Throop  Lori M. Feaga 《Icarus》2011,214(2):394-399

The European Space Agency’s Rosetta spacecraft, en route to a 2014 encounter with comet 67P/Churyumov-Gerasimenko, made a gravity assist swing-by of Mars on 25 February 2007, closest approach being at 01:54 UT. The Alice instrument on board Rosetta, a lightweight far-ultraviolet imaging spectrograph optimized for in situ cometary spectroscopy in the 750-2000 Å spectral band, was used to study the daytime Mars upper atmosphere including emissions from exospheric hydrogen and oxygen. Offset pointing, obtained five hours before closest approach, enabled us to detect and map the H i Lyman-α and Lyman-β emissions from exospheric hydrogen out beyond 30,000 km from the planet’s center. These data are fit with a Chamberlain exospheric model from which we derive the hydrogen density at the 200 km exobase and the H escape flux. The results are comparable to those found from the Ultraviolet Spectrometer experiment on the Mariner 6 and 7 fly-bys of Mars in 1969. Atomic oxygen emission at 1304 Å is detected at altitudes of 400-1000 km above the limb during limb scans shortly after closest approach. However, the derived oxygen scale height is not consistent with recent models of oxygen escape based on the production of suprathermal oxygen atoms by the dissociative recombination of .  相似文献   

Highly localised distribution patterns of juvenile sea cucumber Australostichopus mollis     

MJ Slater  AG Carton  AG Jeffs 《新西兰海洋与淡水研究杂志》2013,47(4):201-216

Information on the environmental characteristics of the juvenile habitat of many deposit-feeding sea cucumber species is limited, despite most fished species exhibiting rapid localised depletion. The current study combined large and small scale surveying techniques within a New Zealand harbour to identify areas with high densities of juvenile Australostichopus mollis, a commercially valuable aspidochirote holothurian. Data from detailed surveys were used to relate densities of juveniles and adults with measures of physical habitat characteristics including depth, sediment facies type, grain size range, as well as measures of chlorophyll-a, phaeopigment, carbon and nitrogen content of surface sediment. Results revealed a highly localised distribution of juvenile A. mollis focused on one site associated with an area of high adult density. Sites of high juvenile A. mollis density were characterised by sediment qualities favouring epibenthic detritivorous deposit feeding, including high nitrogen content, high phaeopigment:chlorophyll-a ratio and small grain size. The high-density juvenile site had facies that were further characterised by the presence of large shell fragments (>10 cm length) of the horse mussel (Atrina zelandica), which may provide a unique settlement microhabitat for early juveniles. Unlike some other sea cucumber species, juvenile A. mollis shows no distinct spatial separation from adult sea cucumbers, no association with dense macroalgae and no clear preference for shallower depths than adults. Overall, the results illustrate the highly localised pattern of recruitment of this species to a widely distributed adult population, which may help to explain the lack of previous observations of juveniles in this species. These results indicate the importance of identifying and protecting what appear to be very specific juvenile habitats in deposit-feeding sea cucumbers to ensure continuing recruitment to exploited populations.  相似文献   

Expansion rate and geometry of floating vegetation mats on the margins of thermokarst lakes,northern Seward Peninsula,Alaska, USA     

Andrew D. Parsekian  Benjamin M. Jones  Miriam Jones  Guido Grosse  Katey M. Walter Anthony  Lee Slater 《地球表面变化过程与地形》2011,36(14):1889-1897

Investigations on the northern Seward Peninsula in Alaska identified zones of recent (<50 years) permafrost collapse that led to the formation of floating vegetation mats along thermokarst lake margins. The occurrence of floating vegetation mat features indicates rapid degradation of near‐surface permafrost and lake expansion. This paper reports on the recent expansion of these collapse features and their geometry is determined using geophysical and remote sensing measurements. The vegetation mats were observed to have an average thickness of 0.57 m and petrophysical modeling indicated that gas content of 1.5–5% enabled floatation above the lake surface. Furthermore, geophysical investigation provides evidence that the mats form by thaw and subsidence of the underlying permafrost rather than terrestrialization. The temperature of the water below a vegetation mat was observed to remain above freezing late in the winter. Analysis of satellite and aerial imagery indicates that these features have expanded at maximum rates of 1–2 m yr^‐1 over a 56 year period. Including the spatial coverage of floating ‘thermokarst mats’ increases estimates of lake area by as much as 4% in some lakes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献