Adjusting wavelet‐based multiresolution analysis boundary conditions for long‐term streamflow forecasting          下载免费PDF全文

I. Maslova  A. M. Ticlavilca  M. McKee 《水文研究》2016,30(1):57-74

We propose a novel technique for improving a long‐term multi‐step‐ahead streamflow forecast. A model based on wavelet decomposition and a multivariate Bayesian machine learning approach is developed for forecasting the streamflow 3, 6, 9, and 12 months ahead simultaneously. The inputs of the model utilize only the past monthly streamflow records. They are decomposed into components formulated in terms of wavelet multiresolution analysis. It is shown that the model accuracy can be increased by using the wavelet boundary rule introduced in this study. A simulation study is performed to evaluate the effects of different wavelet boundary rules using synthetic and real streamflow data from the Yellowstone River in the Uinta Basin in Utah. The model based on the combination of wavelet and Bayesian machine learning regression techniques is compared with that of the wavelet and artificial neural networks‐based model. The robustness of the models is evaluated. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Tavui Volcano: neighbour of Rabaul and likely source of the Middle Holocene penultimate major eruption in the Rabaul area     

Chris O. McKee 《Bulletin of Volcanology》2015,77(9):1-21

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Evaporation and the subcanopy energy environment in a flooded forest          下载免费PDF全文

Scott T. Allen  Michele L. Reba  Brandon L. Edwards  Richard F. Keim 《水文研究》2017,31(16):2860-2871

The combination of tree canopy cover and a free water surface makes the subcanopy environment of flooded forested wetlands unlike other aquatic or terrestrial systems. Subcanopy vapour fluxes and energy budgets represent key controls on water level and understorey climate but are not well understood. In a permanently flooded forest in south‐eastern Louisiana, USA, an energy balance approach was used to address (a) whether evaporation from floodwater under a forest canopy is solely energy limited and (b) how energy availability was modulated by radiation and changes in floodwater heat storage. A 5‐month continuous measurement period (June–November) was used to sample across seasonal changes in canopy activity and temperature regimes. Over this period, the subcanopy airspace was humid, maintaining saturation vapour pressure for 28% of the total record. High humidity coupled with the thermal inertia of surface water altered both seasonal and diel energy exchanges, including atypical phenomena such as frequent day‐time vapour pressure gradients towards the water surface. Throughout the study period, nearly all available energy was partitioned to evaporation, with minimal sensible heat exchange. Monthly mean evaporation ranged from 0.7 to 1.7 mm/day, peaking in fall when canopy senescence allowed greater radiation transmission; contemporaneous seasonal temperature shifts and a net release of stored heat from the surface water resulted in energy availability exceeding net radiation by 30% in October and November. Relatively stable energy partitioning matches Priestley–Taylor assumptions for a general model of evaporation in this ecosystem.  相似文献   

Crack azimuths on Europa: time sequence in the southern leading face     

Alyssa Rose Sarid  Gregory V. Hoppa  Brandon Preblich 《Icarus》2004,168(1):144-157

The formation sequence of prominent ridges and other tectonic lineaments on the southern portion of the leading hemisphere of Europa is determined from cross-cutting relationships. These selected features formed fairly recently relative to most of the surface; older lineaments no longer retain clear evidence of cross-cutting. If we assume that this sequence represents the order of formation of cracks that underlie each lineament, and that the orientation of each crack was determined by tidal stress whose azimuth varies monotonically counter-clockwise with time, the azimuth must have rotated more than 740°, which would correspond to the change in tidal stress over two periods of nonsynchronous rotation (relative to the direction of Jupiter). However, that interpretation is not necessarily compelling, because the observed orientations of cross-cutting lineaments are not densely spaced over these cycles; in fact, the sequence would fit nearly as well into an arbitrary model with rotation in the opposite sense from that predicted by theory. This tectonic record may have formed over many more rotational cycles, such that typically only a few cracks form per cycle, which would be consistent with evidence from considerations of cycloidal crack patterns. Sets of cracks that cluster near certain azimuth orientations appear to be parts of globe-encircling lineament systems and may result from other effects, perhaps polar wander that occurred rapidly relative to nonsynchronous rotation.  相似文献   

The shape of galaxy cluster dark matter haloes: systematics of its imprint on cluster gas and comparison to observations     

Ricardo A. Flores  Brandon Allgood  rey V. Kravtsov  Joel R. Primack  David A. Buote  James S. Bullock 《Monthly notices of the Royal Astronomical Society》2007,377(2):883-896

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Small‐scale variability in surface moisture on a fine‐grained beach: implications for modeling aeolian transport     

Brandon L. Edwards  Steven L. Namikas 《地球表面变化过程与地形》2009,34(10):1333-1338

Small‐scale variations in surface moisture content were measured on a fine‐grained beach using a Delta‐T Theta probe. The resulting data set was used to examine the implications of small‐scale variability for estimating aeolian transport potential. Surface moisture measurements were collected on a 40 cm × 40 cm grid at 10 cm intervals, providing a total of 25 measurements for each grid data set. A total of 44 grid data sets were obtained from a representative set of beach sub‐environments. Measured moisture contents ranged from about 0% (dry) to 25% (saturated), by weight. The moisture content range within a grid data set was found to vary from less than 1% to almost 15%. The magnitude of within‐grid variability varied consistently with the mean moisture content of the grid sets, following an approximately normal distribution. Both very wet and very dry grid data sets exhibited little internal variability in moisture content, while intermediate moisture contents were associated with higher levels of variability. Thus, at intermediate moisture contents it was apparent that some portions of the beach surface could be dry enough to allow aeolian transport (i.e. moisture content is below the critical threshold), while adjacent portions are too wet for transport to occur. To examine the implications of this finding, cumulative distribution functions were calculated to model the relative proportions of beach surface area expected to be above or below specified threshold moisture levels (4%, 7%, and 14%). It was found that the implicit inclusion of small‐scale variability in surface moisture levels typically resulted in changes of less than 1% in the beach area available for transport, suggesting that this parameter can be ignored at larger spatial scales. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Exhuming the Alps through time: clues from detrital zircon fission-track thermochronology     

M. Bernet  M. Brandon  J. Garver†  M. L. Balestieri‡  B. Ventura§  M. Zattin¶ 《Basin Research》2009,21(6):781-798

The European Alps are a mountain belt that is characterized by a series of discrete orogenic events, which have long been recognized. Despite the inherent episodic nature of orogenic evolution, the Alps have been continuously exhumed, mainly by erosion, but also by normal faulting. Since continental collision started in the late Eocene/Early Oligocene evidence for ongoing erosional exhumation has been preserved in synorogenic sediments that accumulated in basins adjacent to the pro- and retro-side of this double-vergent mountain belt. This long-term erosion record can be used to determine exhumation rates. Lag-times calculated from fission-track (FT) ages of detrital zircon from synorogenic sediments are fairly constant for the European Alps since the Oligocene–Late Miocene. Although the fast exhuming areas were unroofed at rates of 0.4–0.7 km Myr⁻¹, the overall average exhumation rate is between 0.2 and 0.3 km Myr⁻¹ on a regional scale. The detrital and bedrock zircon FT data of the Alps do not detect the increase in erosion rates since the Pliocene over the past ∼5 Myr, as shown elsewhere. This increase cannot be detected yet with the detrital zircon FT method because not enough rock has been removed to widely expose zircons with Pliocene or younger cooling ages in the Alps. Long term (30 Myr) exhumation rates appear to have been approximately constant when averaged over a sliding time window of about 8 Myr, or depth window of 5 to 10 km (ZFT closure depths); shorter-term fluctuations are not identified using this method.  相似文献   

Test of the climatological dispersion model in the strait of canso area,Nova Scotia     

R.W. Shaw  E.W. Brandon 《大气与海洋》2013,51(4):265-276

Abstract

The Climatological Dispersion Mode1 is used to estimate mean annual and mean monthly concentrations of sulphur dioxide in the Strait of Canso area of Noua Scotia. It is found that the wind distribution at the southern end of the Strait is more likely to produce a reliable estimate of the concentration of pollutants from the taller stacks, whereas the surface wind distribution from a central location in the Strait can be used, because of low‐level channelling, to estimate concentrations of pollutants from the lower sources. Data on winds aloft over the Strait, are utilized in support of this thesis. The procedure does not apply well to the summer months; otherwise the resulting patterns of predicted concentrations of sulphur dioxide are generally consistent with observed values. More accurate and sensitive instruments are needed in future studies of long‐term average conditions.  相似文献   

Direct Fourier transform mass spectral analysis of natural waters with low dissolved organic matter     

Rachel L. Sleighter  Georgina A. McKee  Patrick G. Hatcher 《Organic Geochemistry》2009,40(1):119-125

A major obstacle for characterizing dissolved organic matter (DOM) with ultrahigh resolution mass spectrometry has been its low concentrations in natural waters. Many previous mass spectrometric studies of both terrestrial and marine DOM typically have isolated and concentrated the DOM using solid phase C₁₈ extraction disks, ultrafiltration, or XAD resins, all of which are known to discriminate against many different classes of compounds. We have, for the first time, developed an approach to directly analyze natural water samples with less than 6 mg/l DOC (dissolved organic carbon), using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). We demonstrate the sensitivity and ability of sequential selective ion accumulation (SSIA) to detect the thousands of components in a single freshwater DOM sample without any significant pretreatment. By utilizing SSIA, the baseline noise decreases while signal to noise ratios of the peaks increase, allowing for approximately 40% more formulas to be assigned to peaks in the mass spectra.  相似文献   

Direct shear testing of polished slickensided surfaces     

Christopher L. Meehan  Thomas L. Brandon  J. Michael Duncan  Binod Tiwari 《Landslides》2010,7(2):157-167

A series of ring shear and direct shear tests were performed to measure the drained residual strength of three clay soils. For each of the soils, slickensided direct shear specimens were prepared by wire-cutting intact specimens, and polishing the resulting shear plane on a variety of surfaces to align the clay particles in the direction of shear. Drained direct shear tests were then conducted on each of the polished specimens. The resulting shear strengths were compared with the residual strengths measured in the ring shear device to evaluate the effectiveness of the different polishing techniques for creating slickensided surfaces. Test results indicated that the measurement of residual strengths along preformed slickensided surfaces is extremely sensitive to both the soil type and the slickenside preparation technique that is used. Consequently, this approach does not appear to be a viable alternative to conventional repeated direct shear or ring shear tests to measure residual shear strengths.  相似文献