Shifting level modelling of hydrologic series     

Jose D. Salas  Duane C. Boes 《Advances in water resources》1980,3(2):59-63

The potential of applying shifting level (SL) models to hydrologic processes is discussed in light of observed statistical characteristics of hydrologic data. An SL model and an ARMA (1, 1) model are fitted to an actual hydrologic series. Computer simulation experiments with these models are carried out to compare maximum accumulated deficit and run properties. Results obtained indicate that the mean maximum accumulated deficit, mean longest negative run length, and mean largest negative run sum for both models are similar while there are differences in their corresponding variances.  相似文献   

Dating Early and Middle (Reid) Pleistocene Glaciations in Central Yukon by Tephrochronology     

John A. Westgate  Shari J. Preece  Duane G. Froese  Robert C. Walter  Amanjit S. Sandhu  Charles E. Schweger 《Quaternary Research》2001,56(3)

The late Cenozoic deposits of central Yukon contain numerous distal tephra beds, derived from vents in the Wrangell Mountains and Aleutian arc–Alaska Peninsula region. We use a few of these tephra beds to gain a better understanding on the timing of extensive Pleistocene glaciations that affected this area. Exposures at Fort Selkirk show that the Cordilleran Ice Sheet advanced close to the outer limit of glaciation about 1.5 myr ago. At the Midnight Dome Terrace, near Dawson City, exposed outwash gravel, aeolian sand, and loess, related to valley glaciers in the adjacent Ogilvie Mountains, are of the same age. Reid glacial deposits at Ash Bend on the Stewart River are older than oxygen isotope stage (OIS) 6 and likely of OIS 8 age, that is, about 250,000 yr B.P. Supporting evidence for this chronology comes from major peaks in the rates of terrigeneous sediment input into the Gulf of Alaska at 1.5 and 0.25 myr B.P.  相似文献   

Dispersion Modelling of the Kilauea Plume   总被引：1，自引：0，他引：1  

Annette T. Hollingshead  Steven Businger  Roland Draxler  John Porter  Duane Stevens 《Boundary-Layer Meteorology》2003,108(1):121-144

Emissions from the Kilauea volcano pose significant environmental and health risksto the Hawaiian community. This paper describes progress toward simulating theconcentration and dispersion of plumes of volcanic aerosol after they emanate from thePu'u O'o vent of the Kilauea volcano.In order to produce an accurate regional forecast of the concentration and dispersionof volcanic aerosol, the Hybrid Single-Particle Lagrangian Integrated Trajectory(HY-SPLIT) model was used. Wind fields and thermodynamic data from the non-hydrostatic Mesoscale Spectral Model (MSM) were employed as input for theHY-SPLIT model. A combination of satellite remote sensing, aircraft, and ground-based observations collected during a field experiment was used to validate the model simulation of aerosol distribution.The HY-SPLIT model shows skill in reproducing the plume shape, orientation, and concentration gradients as deduced from satellite images of aerosol optical depth.Comparison of the modelled and observed values suggests that the model was able to produce reasonable plume concentrations and spatial gradients downwind of the source. Model concentrations were generally less than those observed on the leeward side of the Island of Hawaii. This deficiency may be explained by a lack of (i) background concentrations, (ii) local sources of pollution and/or (iii) sea-breeze circulation in the prognostic input wind field. These results represent early progress toward the goal of future operational application of the HY-SPLIT model to predict volcanic aerosol concentrations in Hawaii. This may help mitigate their negative impacts of plumes respiratory health, agriculture, and general aviation.  相似文献   

Carbon Stores, Sinks, and Sources in Forests of Northwestern Russia: Can We Reconcile Forest Inventories with Remote Sensing Results?     

Olga N. Krankina  Mark E. Harmon  Warren B. Cohen  Doug R. Oetter  Zyrina Olga  Maureen V. Duane 《Climatic change》2004,67(2):257-272

Forest inventories and remote sensing are the two principal data sources used to estimate carbon (C) stocks and fluxes for large forest regions. National governments have historically relied on forest inventories for assessments but developments in remote sensing technology provide additional opportunities for operational C monitoring. The estimate of total C stock in live forest biomass modeled from Landsat imagery for the St. Petersburg region was consistent with estimates derived from forest inventory data for the early 1990s (272 and 269 TgC, respectively). The estimates of mean C sink in live forest biomass also agreed well (0.36 and 0.34 Mg C ha^–1 yr^–1). Virtually all forest lands were accumulating C in live biomass, however when the net change in total ecosystem C stock was considered, 19% of the forest area were a net source of C. The average net C sink in total ecosystem biomass is quite weak (0.08 MgC ha^–1 yr^–1 and could be reversed by minor increases in harvest rates or a small decline in biomass growth rates.  相似文献   

Brine expulsion, fluid transport and metallization spanning 2.0 Gyr in basins of southern and central Africa   总被引：1，自引：0，他引：1  

M. J. Duane  E. P. Saggerson 《Basin Research》1995,7(1):97-108

Mineral provinces in southern and central Africa are strongly controlled by major structural trends, the alignment of sedimentary basins and metamorphically induced thermal regimes deep in the crust. Ore deposits are preferentially located on cooler margins of orogenic belts and are ultimately end-products of fluid expulsion out of the deeper parts of orogenic axes. Metamorphic and structural vectors within orogenic belts adjacent to major cratons show a trend of high-grade thermal overprinting in the cores of axes and lower metamorphic regimes acting on the distal margins of orogens (e.g. foreland basins). This apparent pattern is considered to have importance in the expulsion of at least three generations of mineralizing fluids beginning with exhalative migration during diagenesis and culminating much later in thrust-controlled expulsion onto adjacent craton margins. Fluids within the hydrosphere that accumulate initially through topographic gradients in the sediments mixed with components of the mantle (CO₂). After storage within the crust, migration, enforced by metamorphic processes, transferred fluids out of, and away from, high thermal regimes in the axes of belts, leading to their present preservation around the margins of the major cratonic nuclei.  相似文献   

Possibility of a layered moon     

Z.F. Danes̆Duane R. McNeely 《Icarus》1971

Recent lunar data can be interpreted as indicating the Moon has a hard “crust” a few km thick, an “asthenosphere” about a hundred km thick, and a high viscosity “lower mantle.”  相似文献   

Eruptive history and tectonic setting of Medicine Lake Volcano,a large rear-arc volcano in the southern Cascades     

Julie M. Donnelly-Nolan  Timothy L. Grove  Marvin A. Lanphere  Duane E. Champion  David W. Ramsey 《Journal of Volcanology and Geothermal Research》2008

Medicine Lake Volcano (MLV), located in the southern Cascades ∼ 55 km east-northeast of contemporaneous Mount Shasta, has been found by exploratory geothermal drilling to have a surprisingly silicic core mantled by mafic lavas. This unexpected result is very different from the long-held view derived from previous mapping of exposed geology that MLV is a dominantly basaltic shield volcano. Detailed mapping shows that < 6% of the ∼ 2000 km² of mapped MLV lavas on this southern Cascade Range shield-shaped edifice are rhyolitic and dacitic, but drill holes on the edifice penetrated more than 30% silicic lava. Argon dating yields ages in the range ∼ 475 to 300 ka for early rhyolites. Dates on the stratigraphically lowest mafic lavas at MLV fall into this time frame as well, indicating that volcanism at MLV began about half a million years ago. Mafic compositions apparently did not dominate until ∼ 300 ka. Rhyolite eruptions were scarce post-300 ka until late Holocene time. However, a dacite episode at ∼ 200 to ∼ 180 ka included the volcano's only ash-flow tuff, which was erupted from within the summit caldera. At ∼ 100 ka, compositionally distinctive high-Na andesite and minor dacite built most of the present caldera rim. Eruption of these lavas was followed soon after by several large basalt flows, such that the combined area covered by eruptions between 100 ka and postglacial time amounts to nearly two-thirds of the volcano's area. Postglacial eruptive activity was strongly episodic and also covered a disproportionate amount of area. The volcano has erupted 9 times in the past 5200 years, one of the highest rates of late Holocene eruptive activity in the Cascades. Estimated volume of MLV is ∼ 600 km³, giving an overall effusion rate of ∼ 1.2 km³ per thousand years, although the rate for the past 100 kyr may be only half that. During much of the volcano's history, both dry HAOT (high-alumina olivine tholeiite) and hydrous calcalkaline basalts erupted together in close temporal and spatial proximity. Petrologic studies indicate that the HAOT magmas were derived by dry melting of spinel peridotite mantle near the crust mantle boundary. Subduction-derived H₂O-rich fluids played an important role in the generation of calcalkaline magmas. Petrology, geochemistry and proximity indicate that MLV is part of the Cascades magmatic arc and not a Basin and Range volcano, although Basin and Range extension impinges on the volcano and strongly influences its eruptive style. MLV may be analogous to Mount Adams in southern Washington, but not, as sometimes proposed, to the older distributed back-arc Simcoe Mountains volcanic field.  相似文献   

Crying No Wolf: Why Economists Don't Worry about Climate Change, andShould     

Duane Chapman  Neha Khanna 《Climatic change》2000,47(3):225-232

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Pre-glacial and interglacial pollen records over the last 3 Ma from northwest Canada: Why do Holocene forests differ from those of previous interglaciations?     

Charles Schweger  Duane Froese  James M. White  John A. Westgate 《Quaternary Science Reviews》2011,30(17-18):2124-2133

We synthesize pollen spectra from eleven dated stratigraphic sections from central and northern Yukon. Palaeomagnetic and tephra dating indicates the earliest assemblages, representing closed canopy Pinus and Picea forest, are middle-late Pliocene age. More open forest conditions, indicated by increased Poaceae and with evidence of permafrost, are dated at ca 3 Ma. While Pinus pollen is abundant at 3 Ma, it is reduced in records after 2.6 Ma, and subsequent Pleistocene interglacial forest records are repeatedly dominated by Picea, along with Alnus and small but significant amounts of Abies. Surface sample comparisons indicate that Abies was more widespread and abundant in past interglaciations than at present and that Middle-Pleistocene Picea–Abies forest grew in the northern Yukon Porcupine Basin, 500 km beyond modern Abies limits. In contrast, Pinus, which occurs today in southern and central Yukon, was not a significant component of these Pleistocene interglacial forests. Late-Holocene pollen assemblages with rare Abies and high Pinus are the most distinct in the past 2.6 Ma. Possible factors driving Holocene difference are paleoclimate, paludification, changes in megafaunal herbivory and an unusual fire regime. Anthropogenic burning is a factor unique to the Holocene, and if it is shown to be important in this case, it would challenge our notion of what constitutes boreal wilderness.  相似文献   

Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region   总被引：3，自引：0，他引：3  

June-Yi Lee  Bin Wang  Matthew C. Wheeler  Xiouhua Fu  Duane E. Waliser  In-Sik Kang 《Climate Dynamics》2013,40(1-2):493-509

The boreal summer intraseasonal oscillation (BSISO) of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system. Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator. In order to facilitate detection, monitoring and prediction of the BSISO we suggest two real-time indices: BSISO1 and BSISO2, based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S–40°N, 40°–160°E, for the extended boreal summer (May–October) season over the 30-year period 1981–2010. BSISO1 is defined by the first two principal components (PCs) of the MV-EOF analysis, which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward MJO with quasi-oscillating periods of 30–60 days. BSISO2 is defined by the third and fourth PCs, which together mainly capture the northward/northwestward propagating variability with periods of 10–30 days during primarily the pre-monsoon and monsoon-onset season. The BSISO1 circulation cells are more Rossby wave like with a northwest to southeast slope, whereas the circulation associated with BSISO2 is more elongated and front-like with a southwest to northeast slope. BSISO2 is shown to modulate the timing of the onset of Indian and South China Sea monsoons. Together, the two BSISO indices are capable of describing a large fraction of the total intraseasonal variability in the ASM region, and better represent the northward and northwestward propagation than the real-time multivariate MJO (RMM) index of Wheeler and Hendon.  相似文献