Incorporation of internal fluctuations in a meandering plume model of concentration fluctuations     

Eugene Yee  R. Chan  P. R. Kosteniuk  G. M. Chandler  C. A. Biltoft  J. F. Bowers 《Boundary-Layer Meteorology》1994,67(1-2):11-39

A meandering plume model that explicitly incorporates the effects of small-scale structure in the instantaneous plume has been formulated. The model requires the specification of two physically based input parameters; namely, the meander ratio,M, which is dependent on the ratio of the meandering plume dispersion to the instantaneous relative plume dispersion and, a relative in-plume fluctuation measure,k, that is related inversely to the fluctuation intensity in relative coordinates. Simple analytical expressions for crosswind profiles of the higher moments (including the important shape parameters such as fluctuation intensity, skewness, and kurtosis) and for the concentration pdf have been derived from the model. The model has been tested against some field data sets, indicating that it can reproduce many key aspects of the observed behavior of concentration fluctuations, particularly with respect to modeling the change in shape of the concentration pdf in the crosswind direction.List of Symbols C Mean concentration in absolute coordinates - C _r Mean concentration in relative coordinates - C₀ Centerline mean concentration in absolute coordinates - C _r,0 Centerline mean concentration in relative coordinates - f Probability density function of concentration in absolute coordinates - f _c Probability density function of plume centroid position - f _r Probability density function of concentration in relative coordinates - i Absolute concentration fluctuation intensity (standard deviation to mean ratio) - i _r Relative concentration fluctuation intensity (standard deviation to mean ratio) - k Relative in-plume fluctuation measure:k=1/i _r ² - K Concentration fluctuation kurtosis - M Meander ratio of meandering plume variance to relative plume variance - S Concentration fluctuation skewness - x Downwind distance from source - y Crosswind distance from mean-plume centerline - z Vertical distance above ground - Instantaneous (random) concentration - Crosswind dispersion ofnth concentration moment about zero - _ny Mean-plume crosswind (absolute) dispersion - _y Plume centroid (meandering) dispersion in crosswind direction - _y,c Instantaneous plume crosswind (relative) dispersion - Normalized mean concentration in absolute coordinates:C/C ₀ - Particular value taken on by instantaneous concentration,   相似文献   

A numerical study of the influence of an air temperature-inversion layer and a seawater density-jump layer on the structure of interacting boundary layers     

Le Ngoc Ly  Eugene S. Takle 《Boundary-Layer Meteorology》1994,67(4):327-343

The effects of an air-temperature inversion in the atmosphere and a seawater density jump in the ocean on the structure of the atmospheric and oceanic boundary layers are studied by use of a coupled model. The numerical model consists of a closed system of equations for velocities, turbulent kinetic energy, turbulent exchange coefficient, local turbulent length scale, and stratification expressions for both air and sea boundary layers. The effects of the temperature inversion and the density jump are incorporated into the equations of turbulent kinetic energy of the atmosphere and ocean by a parameterization. A series of numerical experiments was conducted to determine the effects of various strengths of the inversion layer and surface heat fluxes in the atmosphere and of the density-jump layer in the ocean on the structure of the interacting boundary layers.The numerical results show that the temperature inversion in the atmosphere and density jump in the ocean have strong influences on turbulent structure [especially on the turbulent exchange coefficient (TEC) and turbulent kinetic energy (TKE)] and on air-sea interaction characteristics. Maxima of TKE and TEC strongly decrease with increasing strength of the inversion layer, and they disappear for strong inversions in the atmosphere. Certain strengths (density differences between the upper and the lower layers) of the density-jump layer in the ocean (₂ 0.1 g/cm³) produce double maxima in TEC-profiles and TKE-profiles in the ocean. The magnitudes of air-sea interaction characteristics such as geostrophic drag coefficient, and surface drift current increase with increasing strength of the density-jump layer in the ocean. The density-jump layer plays the role of a barrier that limits vertical mixing in the ocean. The numerical results agree well with available observed data and accepted quantitive understanding of the influences of a temperature inversion layer and a density-jump layer on the interacting atmospheric and oceanic boundary layers.  相似文献   

On the moments approximation method for constructing a Lagrangian Stochastic model     

Shuming Du  John D. Wilson  Eugene Yee 《Boundary-Layer Meteorology》1994,70(3):273-292

The exact Eulerian velocity probability density function (pdf) of a turbulent field is generally unknown, and one normally has available only partial information in the form of low order moments. We compare two alternative Lagrangian Stochastic (LS) approaches formed from this partial information, (i) the moments approximation approach (Kaplan and Dinar, 1993); and (ii) the well-mixed model (Thomson, 1987) that corresponds to the maximum missing information pdf formed from the available information. We show that the moments approximation model does not in general satisfy the well-mixed constraint, and can give an inferior prediction of dispersion.  相似文献   

Probability Theory as Logic: Data Assimilation for Multiple Source Reconstruction     

Eugene?YeeEmail author 《Pure and Applied Geophysics》2012,169(3):499-517

Probability theory as logic (or Bayesian probability theory) is a rational inferential methodology that provides a natural and logically consistent framework for source reconstruction. This methodology fully utilizes the information provided by a limited number of noisy concentration data obtained from a network of sensors and combines it in a consistent manner with the available prior knowledge (mathematical representation of relevant physical laws), hence providing a rigorous basis for the assimilation of this data into models of atmospheric dispersion for the purpose of contaminant source reconstruction. This paper addresses the application of this framework to the reconstruction of contaminant source distributions consisting of an unknown number of localized sources, using concentration measurements obtained from a sensor array. To this purpose, Bayesian probability theory is used to formulate the full joint posterior probability density function for the parameters of the unknown source distribution. A simulated annealing algorithm, applied in conjunction with a reversible-jump Markov chain Monte Carlo technique, is used to draw random samples of source distribution models from the posterior probability density function. The methodology is validated against a real (full-scale) atmospheric dispersion experiment involving a multiple point source release.  相似文献   

Stratigraphic relations of australites in the Port Campbell Embayment,Victoria     

Eugene M. SHOEMAKER  H. Ralph UHLHERR 《Meteoritics & planetary science》1999,34(3):369-384

Abstract— In the Port Campbell Embayment of Victoria, australites have been found in situ in channel deposits of the Hanson Plain Sand of Pliocene and Pleistocene age. The large majority of the australites, however, occur as a lag deposit at the basal contact of the Sturgess Sand of late Pleistocene and Holocene age and are spatially correlated with ferruginous sandstone clasts that are derived from the Hanson Plain Sand. Some of the tektites are imbedded in or bonded to the ferruginous sandstone clasts, but most are found as individual tektite fragments. A few percent of the tektites have nearly perfectly preserved, complete aerodynamically shaped forms. The sandstone clasts and associated tektites have been reworked from the much older underlying Hanson Plain and have been locally concentrated in the lag deposit. Some tektites also occur at higher levels in the Sturgess Sand, almost invariably in association with stone flakes, exotic stones transported by the aborigines and, locally, with middens of mollusc shells. Circumstantial evidence indicates that the aborigines transported the tektites found in the upper part of the Sturgess, particularly at Stanhope Bay. As Port Campbell australites unequivocally occur in strata much older than the late Pleistocene and Holocene Sturgess, there is no longer any conflict between the apparent stratigraphic age of the tektites and the middle Pleistocene ages obtained by various chronometric methods.  相似文献   

Variation in maturity-at-age and size in three populations of American plaice   总被引：7，自引：5，他引：2  

Morgan  M. J.; Colbourne  E. B. 《ICES Journal of Marine Science》1999,56(5):673-688

  相似文献   

Interactions Between the Atmospheric Sciences and Insurers in the United States   总被引：1，自引：0，他引：1  

Stanley A. Changnon  E. Ray Fosse  Eugene L. Lecomte 《Climatic change》1999,42(1):51-67

Insurance and insurers are directly affected and concerned about climate fluctuations in the United States. Growing losses in the 1990s awakened many in the insurance business to the enormity of weather-related problems they faced and a need for better information about climate and its fluctuations including a new potential problem, climate change. This paper presents the views of experts from the crop insurance sector, the property-casualty insurance sector, and from the atmospheric sciences sector based on atmospheric research accomplished for the insurance industry for decades. The paper addresses how climatologists and insurers can and need to work together to effectively bring understanding and wise consideration of climate conditions and their future fluctuations and extremes to insurers. Considerable climatological analyses have been employed in the past by the crop insurance industry, but less by property insurers. Insurers can adjust to a change in climate but to do so will require clear evidence, which does not exist now for the United States, and an understanding as well as wide acceptance of the on-going change by regulators and the buying public. Atmospheric scientists can help insurers to mitigate weather losses, to assess risks, to measure critical perils, to educate about risks, and to learn about critical issues like climate change and long-range forecasts.  相似文献   

Chronic light reduction reduces overall resilience to additional shading stress in the seagrass Halophila ovalis     

Siti M. Yaakub  Eugene Chen  Tjeerd J. Bouma  Paul L.A. Erftemeijer  Peter A. Todd 《Marine pollution bulletin》2014

Seagrasses have substantial capacity to survive long periods of light reduction, but how acclimation to chronic low light environments may influence their ability to cope with additional stress is poorly understood. This study examines the effect of temporal light reduction by adding two levels of shading to Halophila ovalis plants in two meadows with different light histories, one characterized by a low light (turbid) environment and the other by a relatively high light (clear) environment. Additional shading resulted in complete mortality for both shading treatments at the turbid site while the clear site showed a pattern of decreased shoot density and increased photochemical efficiency (F_v/F_m) with increased shading. These contrasting results for the same species in two different locations indicate that acclimation to chronic low light regimes can affect seagrass resilience and highlights the importance of light history in determining the outcome of exposure to further (short-term) stress.  相似文献   

Handbook of seafloor sonar imagery P. BLONDEL and B. J. MURTON Publisher John Wiley & Sons,Chichester/Praxis Publishing,Chichester 1997 (314 pp) £75.00 ISBN 0‐471‐96217‐1     

Eugene W. Domack 《第四纪科学杂志》2000,15(6):659-659

  相似文献   

Archaeoseismology     

Eugene S. Schweig 《Geoarchaeology》1998,13(5):528-530

  相似文献