Simulation of daily precipitation in the Pacific Northwest using a weather classification scheme     

Larry L. Wilson  Dennis P. Lettenmaier  Eric F. Wood 《Surveys in Geophysics》1991,12(1-3):127-142

A weather classification scheme was coupled with a semi-Markov model to represent the coincident occurrence of rain/no rain states at a single rain gauge and classes representing regional atmospheric circulation patterns, as identified from National Meteorological Center gridded observations for a large area of the North Pacific. Weather classes were identified from daily observations of surface pressure and 850 mb pressure height at five selected ten degree latitude by ten degree longitude cells using a K-means clustering algorithm, which was applied on a month-by-month basis. The number of climate classes, K, for each month was chosen based on a preliminary analysis of the model's ability to describe statistics of observed precipitation occurrences at the Stampede Pass, Washington weather station. The length of stay distributions within each precipitation occurrence/weather class were assumed to be geometric, and the precipitation amounts for each class and season were fitted with a mixed exponential distribution. Parameters of the length of stay distributions, transition probabilities, and precipitation amounts were estimated from the period of record 1975–84.The fitted model was used to simulate a ten year sequence of daily precipitation. It was found that the semi-Markov model of climate class/wet-dry states preserved the length of wet and dry day runs reasonably well, with the exception of months with long average run lengths. Likewise, the occurrence frequencies of the climate classes were reasonably well preserved with a few exceptions. An exploratory analysis of the properties of wet and dry period runs for those classes and months whose run frequencies were poorly preserved showed that the log survivor functions and variance time curves were also poorly preserved, which suggests that more complex distributions may be required for some of the run length distributions.  相似文献   

Subsolidus physical and chemical mixing of granite and gabbro during mylonitization, South Victoria Land, Antarctica     

C. Rachel Walcott  Dave Craw 《Journal of Structural Geology》1993,15(12)

At Dromedary Massif, Southern Victoria Land, Antarctica, a suite of coarse-grained granite dykes cross-cuts a gabbro pluton which has been partially metamorphosed at amphibolite facies. During regional deformation, strain has been inhomogeneously distributed through the gabbro pluton and has been concentrated in granite dykes. In zones of relatively high strain, the granite dykes have developed a mylonitic fabric. A high strain gradient between granitic mylonite and metagabbroic host rock has induced isochemical mylonitization of the margin of the host. This grain size reduction allowed chemical diffusion between granitic and metagabbroic mylonites, resulting in a marginal zone of biotite-rich mylonite with intermediate composition. Biotite-rich mylonite decoupled from metagabbroic mylonite and flowed with granitic mylonite. Continued folding and transposition of granitic mylonite and biotite-rich mylonite has produced compositionally banded mylonite zones through thorough and irreversible mixing of the two lithologies.  相似文献   

Wind flows and forces in a model spruce forest   总被引：3，自引：1，他引：3  

G. R. Stacey  R. E. Belcher  C. J. Wood  B. A. Gardiner 《Boundary-Layer Meteorology》1994,69(3):311-334

Wind tunnel tests have been conducted on a 1:75 scale model of a Sitka spruce forest in a correctly scaled turbulent boundary-layer flow. 12000 tree models were manufactured with mass, flexibility and aerodynamic drag characteristics chosen to give dynamical similarity with typical 15 m trees in a 30ms^–1 gale. To measure the dynamic response of a sample tree, set within this model forest, a miniature, fast response strain-gauge balance was designed and built. Linked to a computer for on-line data sampling, this balance provided measurements of the fluctuating along-wind and acrosswind components of the overturning moment at ground level, leading to values of mean and extreme moments and the frequency spectrum of the sway motion. Associated measurements of local wind flow characteristics were made with hot-wire anemometers and a laser anemometer. The response of the tree has the characteristics of classical lightly damped vibration and there is evidence that resonant sway motion increases the extreme overturning moments significantly above the values produced by wind gust forces alone.  相似文献   

Magnetite activities across the MgAl2O4-Fe3O4 spinel join,with application to thermobarometric estimates of upper mantle oxygen fugacity     

Glen S. Mattioli  Bernard J. Wood 《Contributions to Mineralogy and Petrology》1988,98(2):148-162

The activity of Fe₃O₄ component in MgAl₂O₄-Fe₃O₄ spinels has been measured at 900° and 1000° C and 1 atm total pressure using a zirconia oxygen electrolyte. As previously reported for the dilute Fe₃O₄ concentration region (Mattioli and Wood 1986a), magnetite activity at 1000° C is greater than at 900° C at constant Fe₃O₄ mole fraction, for compositions across the MgAl₂O₄-Fe₃O₄ join between 20 and 80 mol% Fe₃O₄ component. The 1-atm solvus crest lies between 900° and 1000° C and, at 900° C the limbs are at Fe₃O₄ mole fractions of 0.2 and 0.6 approximately.Application of the O'Neill and Navrotsky (1983, 1984) cation distribution model indicates that the unusual activity — composition behavior of Fe₃O₄ is caused by changes in the equilibrium state of disorder of mixed MgAl₂O₄-Fe₃O₄ spinels relative to the disordered Fe₃O₄ standard state. In addition, both stoichiometric volumes (Mattioli et al. 1987) and activities across the MgAl₂O₄-Fe₃O₄ join suggest that short range order is significant for this binary. Excess free energy terms must be added to ideal Fe₃O₄ activities formulated from equilibrium cation distributions in complex MgAl₂O₄-Fe₃O₄ spinels in order to increase Fe₃O₄ activities to values consistent with observation and to generate the apparent region of immiscibility at 900° C.We have applied our activity data to the estimation of upper mantle spinel-lherzolite oxygen fugacities. We calculated that minimum 's are about 2 log units below the synthetic QFM buffer at 15 kbar total pressure for Fe₃O₄ concentration of 2 mol%, in a Cr-free spinel phase. If a preliminary calibration of an additional 25 mol% Fe²⁺-substitution as FeCr₂O₄ or FeAl₂O₄ component is incorporated into Fe₃O₄ activity, then olivine-orthopyroxene-spinel assemblages of depleted-Type 1-spinel-lherzolite xenoliths indicate 's close to QFM at 15 kbar. This is in good agreement with previous thermobarometric estimates and in sharp contrast to 1 atm intrinsic measurements near IW.  相似文献   

Sorting and identification techniques for clupeoid larvae     

Nichols  J. H.; Wood  R. J. 《ICES Journal of Marine Science》1978,38(1):48-53

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Modelling of high amplitude internal waves integrating the primitive (Navier–Stokes) equations     

D. J. Wood  J. Grue 《Applied Ocean Research》2002,24(6):331-340

In this paper we use an industrial Navier–Stokes (NS) solver to model high amplitude internal waves. The model simulates a fluid with a shallow upper layer with linear stratification and a deep lower layer with constant density, relevant to conditions in the ocean at several locations. Waves are generated by trapping a volume of light water behind a gate in one end of the numerical wave tank. The velocity and vorticity fields predicted by the model agree well with experiment. The high amplitude waves produced by the NS solver experience an upper bound on the velocity and a broadening in agreement with experiment. These effects have not previously been captured by theoretical models.  相似文献   

Sporormiella as a proxy for non-mammalian herbivores in island ecosystems     

Jamie R. Wood  Janet M. Wilmshurst  Trevor H. Worthy  Alan Cooper 《Quaternary Science Reviews》2011,30(7-8):915-920

Spores of the dung-fungi Sporormiella are routinely used as a proxy for past megaherbivore biomass and to pinpoint the timing of extinctions. Further ecological insight can also be gained into the impacts that followed initial human arrival in a region through correlation of spore abundance with other proxies (e.g. pollen, charcoal). Currently, the use of Sporormiella as a palaeoecological proxy has been restricted to landmasses where large-herbivore guilds are dominated by mammals. Here, we use New Zealand as a case study to show that the method can also be applied effectively to islands dominated by large avian herbivores. We examine 44 dung samples from 7 localities to show that Sporormiella spores were widely distributed in the dung of endemic avian herbivores (South Island takahe (Porphyrio hochstetteri), kakapo (Strigops habroptilus), and several species of extinct moa, identified by ancient DNA analysis). In addition, we show that Sporormiella spores in a forest soil core from the Murchison Mountains, South Island, accurately trace the post-settlement decline of native avian herbivores, and combined with high-resolution radiocarbon dating reveal severely reduced local herbivore populations by the late 17th Century AD. The spores also trace the subsequent spread of Red deer (Cervus elaphus) introduced to the area in the early 20th Century AD. Our results suggest Sporormiella spores may provide a useful new tool for examining extinctions on numerous islands where terrestrial herbivore guilds were dominated by birds or reptiles. Our findings also highlight the need to consider entire herbivore communities (including birds and reptiles) when examining Late Pleistocene continental Sporormiella records, where the focus has often been tracing the decline of populations of large mammals.  相似文献   

An overview of the Lagrangian experiments undertaken during the North Atlantic regional Aerosol Characterisation Experiment (ACE‐2)     

Doug W. Johnson  Simon Osborne  Robert Wood  Karsten Suhre  Randy Johnson  Steven Businger  Patricia K. Quinn  Alfred Wiedensohler  Philip A. Durkee  Lynn M. Russell  Meinrat O. Andreae  Colin O'Dowd  Kevin J. Noone  Brian Bandy  J. Rudolph  Spyros Rapsomanikis 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):290-320

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Experimental quantification of hydrothermal solubility of platinum-group elements with special reference to porphyry copper environments   总被引：4，自引：0，他引：4  

Y. Xiong  S. A. Wood 《Mineralogy and Petrology》2000,68(1-3):1-28

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Evolution of the aerosol, cloud and boundary‐layer dynamic and thermodynamic characteristics during the 2nd Lagrangian experiment of ACE‐2     

Simon R. Osborne  Douglas W. Johnson  Robert Wood  Brian J. Bandy  Meinrat O. Andreae  Colin D. O'Dowd  Paul Glantz  Kevin J. Noone  Christoph Gerbig  Jochen Rudolph  Timothy S. Bates  Patricia Quinn 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):375-400

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