Cloud condensation nuclei and cloud droplet measurements during ACE‐2     

Jefferson R. Snider  Jean&#;Louis Brenguier 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):828-842

During the 2nd Aerosol Characterization Experiment (ACE‐2), relationships between stratocumulus cloud properties and aerosols were examined. Here, the relevant measurements including the cloud condensation nuclei (CCN) activation spectrum, updraft velocity, cloud microphysical and aerosol properties are presented. It is shown that calculations of droplet concentration based on updraft velocity and the CCN activation spectrum are consistent with direct observations. Also discussed is an apparent disparity among measurements of the CCN activation spectrum, the accumulation mode size distribution, and the composition of the submicrometric aerosol. The observed consistency between CCN, updraft and cloud droplets is a necessary refinement; however, extended analyses of the ACE‐2 data set are needed to guide improvements in model simulations of the interaction between aerosols and cloud microphysics. In particular, there is need for an examination of aerosol size spectra and chemical composition measurements with a view towards validating droplet activation schemes which relate the aerosol and cloud dynamical properties to cloud albedo.  相似文献   

Ten guiding principles for the delineation of priority habitat for endangered small cetaceans     

Peter S. Ross  Jay Barlow  Thomas A. Jefferson  Brendan E. Hickie  Tatiana Lee  Christina MacFarquhar  E. Christien Parsons  Kimberly N. Riehl  Naomi A. Rose  Elisabeth Slooten  Chia-Yang Tsai  John Y. Wang  Andrew J. Wright  Shih Chu Yang 《Marine Policy》2011

The adoption of endangered species laws in various nations has intensified efforts to better understand, and protect, at-risk species or populations, and their habitats. In many countries, delineating a portion of a species' habitat as particularly worthy of protection has become a mantra of these laws. Unfortunately, the laws themselves often provide scientists and managers with few, if any, guidelines for how to define such habitat. Conservationists and scientists may view protecting part of the habitat of an endangered species as an ineffectual compromise, while managers may be under pressure to allow a range of human activities within the species' habitat. In the case of small cetaceans, establishing boundaries for such areas can also be complicated by their mobility, the fluid nature of their environment, and the often ephemeral nature of their habitat features. The convergence of multiple human impacts in coastal waters around the world is impacting many small cetaceans (and other species) that rely on these areas for feeding, reproducing, and resting. The ten guiding principles presented here provide a means to characterize the habitat needs of small, at-risk cetaceans, and serve as a basis for the delineation of ‘priority habitat’ boundaries. This conceptual approach should facilitate a constructive discourse between scientists and managers engaged in efforts to recover endangered species. The degree to which the recovery of an at-risk species can be reconciled with sustainable economic activity will depend in part on how well these principles are incorporated into the delineation of priority habitat.  相似文献   

Leaching evaluation of cement stabilisation / solidification treated kaolin clay     

U.E. John  I. Jefferson  D.I. Boardman  G.S. Ghataora  C.D. Hills 《Engineering Geology》2011,(4):315

Sustainable land management often requires redevelopment of existing and often contaminated Brownfield sites over use of Greenfield or agricultural land. Stabilisation / solidification (S/S) offer a viable remediation option with particular suitability in treating heavy metal contaminants. However, uncertainties over long-term durability and previously cheap landfill disposal costs resulted in limited use in many countries. There is a need to characterise treated material and assess components containment and release, to improve S/S confidence and inform remedial design, using the evaluation of the leaching controlling mechanisms. To improve understanding of key features that will enable improvements to such designs, this paper presents an evaluation of leaching for CEM II stabilised kaolin, using the leaching behaviour of 4 main components—aluminium, silicon, calcium and sulphur. Results show no detrimental implications on chemical durability due to kaolin degradation with hydration under induced alkalinity, with increased formation of stable cementitious minerals. Availabilities for components show that aluminium and silicon had minimal leachability compared to total content, whilst calcium and sulphur show almost total leaching availability. Decreasing calcium and silicon leachability under natural chemical conditions with increased hydration duration supports the increased formation of stable cementitious products with time, using the products of kaolin dissociation.  相似文献   

Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range,USA     

A. Jefferson  S.L. Lewis  S.T. Lancaster 《地球表面变化过程与地形》2010,35(7):803-816

Young basalt terrains offer an exceptional opportunity to study landscape and hydrologic evolution through time, since the age of the landscape itself can be determined by dating lava flows. These constructional terrains are also highly permeable, allowing one to examine timescales and process of geomorphic evolution as they relate to the partitioning of hydrologic flowpaths between surface and sub‐surface flow. The western slopes of the Cascade Range in Oregon, USA are composed of a thick sequence of lava flows ranging from Holocene to Oligocene in age, and the landscape receives abundant precipitation of between 2000 and 3500 mm per year. On Holocene and late Pleistocene lava landscapes, groundwater systems transmit most of the recharge to large springs (≥0·85 m³ s^?1) with very steady hydrographs. In watersheds >1 million years old, springs are absent, and well‐developed drainage networks fed by shallow subsurface stormflow produce flashy hydrographs. Drainage density slowly increases with time in this basalt landscape, requiring a million years to double in density. Progressive hillslope steepening and fluvial incision also occur on this timescale. Springs and groundwater‐fed streams transport little sediment and hence are largely ineffective in incising river valleys, so fluvial landscape dissection appears to occur only after springs are replaced by shallow subsurface stormflow as the dominant streamflow generation mechanism. It is proposed that landscape evolution in basalt terrains is constrained by the time required for permeability to be reduced sufficiently for surface flow to replace groundwater flow. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

THE COMPILATION OF A DTM AND A NEW SATELLITE IMAGE MAP FOR KING GEORGE ISLAND,ANTARCTICA     

Matthias Braun  Jefferson Cardia Sim“非汉字符号”es  N.Blindow  Steffen Vogt  U.F.Bremer  M.Pfender  H.Saurer  F.E.Aquino  F.A.Ferron 《地球空间信息科学学报》2001,4(2):47-51

1　ＩｎｔｒｏｄｕｃｔｉｏｎＡｔｐｒｅｓｅｎｔ,ＫｉｎｇＧｅｏｒｇｅＩｓｌａｎｄ (ＫＧＩ)ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｆｒｅｑｕｅｎｔｅｄｓｉｔｅｓｉｎＡｎｔａｒｃｔｉｃａ .Ｉｎｔｏｔａｌ,9ｐｅｒｍａｎｅｎｔｒｅｓｅａｒｃｈｓｔａｔｉｏｎｓａｒｅｉｎｏｐｅｒａｔｉｏｎａｎｄｓｅｖｅｒａｌｒｅｓｅａｒｃｈｃａｂｉｎｓｈａｖｅｂｅｅｎｃｏｎｓｔｒｕｃｔｅｄ .ＤｕｅｔｏｔｈｅｅａｓｙａｃｃｅｓｓｖｉａｔｈｅＣｈｉｌｅａｎａｉｒｓｔｒｉｐｔｈｅｎｕｍ ｂｅｒｏｆｔｈｅｉｓｌａｎｄ’ｓｉｎｈａｂｉｔａｎｔｓｒ…  相似文献   

Holocene ethnobotanical and paleoecological record of human impact on vegetation in the Little Tennessee River Valley, Tennessee     

Paul A. Delcourt  Hazel R. Delcourt  Patricia A. Cridlebaugh  Jefferson Chapman 《Quaternary Research》1986,25(3)

Human occupation and utilization of plant resources have affected vegetation in the lower Little Tennessee River Valley of East Tennessee for 10,000 yr. Changes in Indian cultures and land use are documented by radiocarbon chronologies, lithic artifacts, ceramics, settlement patterns, and ethnobotanical remains from 25 stratified archaeological sites within the Holocene alluvial terrace. The ethnobotanical record consists of 31,500 fragments (13.7 kg) of wood charcoal identified to species and 7.7 kg of carbonized fruits, seeds, nutshells, and cultigens from 956 features. Pollen and plant macrofossils from small ponds both in the uplands and on lower stream terraces record local vegetational changes through the last 1500 to 3000 yr. Human impact increased after cultigens, including squash and gourd, were introduced ca. 4000 yr B.P. during the Archaic cultural period. Forest clearance and cultivation disturbed vegetation on both the floodplain and lower terraces after 2800 yr B.P., during the Woodland period. Permanent Indian settlements and maize and bean agriculture extended to higher terraces 1.5 km from the floodplain by the Mississippian period (1000 to 300 yr B.P.). After 300 yr B.P., extensive land clearance and cultivation by Historic Overhill Cherokee and Euro-Americans spread into the uplands beyond the river valley.  相似文献   

Multiple-chain and other unusual faults in amphiboles   总被引：1，自引：0，他引：1  

D. A. Jefferson  L. G. Mallinson  J. L. Hutchison  J. M. Thomas 《Contributions to Mineralogy and Petrology》1978,66(1):1-4

A combination of high resolution transmission electron microscopy and computer simulation has revealed the existence of multiple-chain and other faults in nephrite jade. Attention is drawn to the subunit cell reorganization involved with many of these faults, which generally appear to be free from severe structural strain.  相似文献   

Production patterns in Massachusetts Bay with outfall relocation     

Candace A. Oviatt  Kimberly J. W. Hyde  Aimee A. Keller  Jefferson T. Turner 《Estuaries and Coasts》2007,30(1):35-46

On September 6, 2000, the sewage outfall at the mouth of Boston Harbor was relocated 15 km offshore to alleviate pollution in Boston Harbor. The expected responses for nutrients and water column productivity parameters were for values to decrease at Boston Harbor, to increase at the outfall location, and to remain unchanged at the boundary of the near field region within 5 km of the outfall. Average values ofr water column measurements from 1992 to 2004 indicated these general responses with some exceptions. At the Harbor, nutrients decreased and chlorophyll increased but¹⁴C primary productivity remained statistically unchanged. At the new outfall location and at the boundary of the near field, nutrients increased and chlorophyll increased but primary productivity remained unchanged. Physical factors affecting primary production, such as pring water temperature, stratification, and wind, had more affects on productivity patters than nutrients from outfall relocation in the near field. A decrease in summer zooplankton after outfall relocation appeared to be due to a region-wide rather than outfall effluents.  相似文献   

Anisotropic Mesh Adaptivity and Control Volume Finite Element Methods for Numerical Simulation of Multiphase Flow in Porous Media   总被引：1，自引：1，他引：0  

Peyman Mostaghimi  James R. Percival  Dimitrios Pavlidis  Richard J. Ferrier  Jefferson L. M. A. Gomes  Gerard J. Gorman  Matthew D. Jackson  Stephen J. Neethling  Christopher C. Pain 《Mathematical Geosciences》2015,47(4):417-440

  相似文献   

Crustal Thermal Structure of the Brazilian Equatorial Margin Using Fourier and Continuous Wavelet Transforms: A Comparative Analysis Based on Different Magnetic Datasets     

Herrera  Duvan Ricardo Herrera  de Castro  David Lopes  Oliveira  Jefferson Tavares Cruz  de Oliveira  Di&#;genes Cust&#;dio 《Surveys in Geophysics》2022,43(3):883-912

Surveys in Geophysics - In this work, we calculated the Curie Point Depth (CPD) for the Brazilian Equatorial Margin using the Fourier and continuous wavelet (CWT) transforms considering a linear...  相似文献