The adjustment of the boundary layer immediately downstream froma coastline is examined based on two levels of eddy correlation data collected on a mast at the shore and six levels of eddy correlation data and profiles of mean variables collected from a mast 2 km offshore during the Risø Air-Sea Experiment. The characteristics of offshore flow are studied in terms of case studies and inter-variable relationships for the entire one-month data set. A turbulent kinetic energy budget is constructed for each case study.The buoyancy generation of turbulence is small compared to shear generation and dissipation. However, weakly stable and weakly unstable cases exhibit completely different vertical structure. With flow of warm air from land over cooler water, modest buoyancy destruction of turbulence and reduced shear generation of turbulence over the less rough sea surface cause the turbulence to rapidly weaken downstream from the coast. The reduction of downward mixing of momentum by the stratification leads to smaller roughness lengths compared to the unstable case. Shear generation at higher levels and advection of stronger turbulence from land often lead to an increase of stress and turbulence energy with height and downward transport of turbulence energy toward the surface.With flow of cool air over a warmer sea surface, a convective internal boundary layer develops downstream from the coast. An overlying relatively thick layer of downward buoyancy flux (virtual temperature flux) is sometimes maintained by shear generation in the accelerating offshore flow. 相似文献
The River Frome was sampled at sub-daily sampling interval, with additional storm sampling, through an annual cycle. Samples were analysed for total phosphorus (TP), soluble reactive phosphorus (SRP), total oxidisable nitrogen (TON) and dissolved reactive silicon (Si). The resulting data set was artificially decimated to mimic sampling frequencies from 12 h to monthly time interval. Monthly sampling interval resulted in significant errors in the estimated annual TP and SRP load of up to 35% and 28% respectively, and the resulting data sets were insufficient to observe peaks in P concentration in response to storm events. Weekly sampling reduced the maximum percentage errors in annual load estimate to 15.4% and 6.5%. TON and silicon concentrations were less variable with changing river flow, and monthly sampling was sufficient to predict annual load estimates to within 10%. However, to investigate within-river nutrient dynamics and behaviour, it is suggested that a weekly sampling interval would be the minimum frequency required for TON and Si studies, and daily sampling would be a minimum requirement to adequately investigate phosphorus dynamics. The loss in nutrient-concentration signal due to reduced sampling interval is presented. Hysteresis in the nutrient concentration/flow relationships for all 32 storm events during the study period were modelled and seasonal patterns discussed to infer nutrient sources and behaviour. The high-resolution monitoring in this study identified, for the first time, major peaks in phosphorus concentration in winter that coincide with sudden falls in air temperature, and was associated with biofilm breakdown. This study has shown that to understand complex catchment nutrient processes, accurately quantify nutrient exports from catchments, and observe changes in water quality as a result of nutrient mitigation efforts over time, it is vital that the newly emerging field-based automated sampler/analyzer technologies begin to be deployed, to allow for routine high-resolution monitoring of our rivers in the future. 相似文献
The world class Jabiluka unconformity-related uranium deposit in the Alligator Rivers Uranium Field, Australia, contains >163,000 tons
of contained U3O8. Mineralization is hosted by shallow-to-steeply dipping basement rocks comprising graphitic units of chlorite–biotite–muscovite
schist. These rocks are overlain by flat-lying coarse-grained sandstones belonging to the Kombolgie Subgroup. The deposit
was discovered in 1971, but has never been mined. The construction of an 1,150 m decline into the upper eastern sector of
the Jabiluka II deposit combined with closely spaced underground drilling in 1998 and 1999 allowed mapping and sampling from
underground for the first time. Structural mapping, drill core logging and petrographic studies on polished thin sections
established a detailed paragenesis that provided the framework for subsequent electron microprobe and X-ray diffraction, fluid
inclusion, and O–H, U–Pb and 40Ar/39Ar isotope analysis. Uranium mineralization is structurally controlled within semi-brittle shears that are sub-conformable
to the basement stratigraphy, and breccias that are developed within the hinge zone of fault-related folds adjacent to the
shears. Uraninite is intimately associated with chlorite, sericite, hematite ± quartz. Electron microprobe and X-ray diffraction
analysis of syn-ore illite and chlorite indicates a mineralization temperature of 200°C. Pre- and syn-ore minerals extracted
from the Kombolgie Subgroup overlying the deposit and syn-ore alteration minerals in the Cahill Formation have δ18Ofluid and δDfluid values of 4.0±3.7 and −27±17‰, respectively. These values are indistinguishable from illite separates extracted from diagenetic
aquifers in the Kombolgie Subgroup up to 70 km to the south and east of the deposit and believed to be the source of the uraniferous
fluid. New fluid inclusion microthermometry data reveal that the mineralising brine was saline, but not saturated. U–Pb and
207Pb/206Pb ratios of uraninite by laser-ablation ICP-MS suggest that massive uraninite first precipitated at ca. 1,680 Ma, which is
coincident with the timing of brine migration out from the Kombolgie Subgroup as indicated by 40Ar/39Ar ages of 1,683±11 Ma from sandstone-hosted illite. Unmineralized breccias cemeted by chlorite, quartz and sericite cross-cut
the mineralized breccias and are in turn cut by straight-sided, high-angle veins of drusy quartz, sulphide and dolomite. U–Pb
and 207Pb/206Pb ratios combined with fluid inclusion and stable isotope data indicate that these post-ore minerals formed when mixing between
two fluids occurred sometime between ca. 1,450 and 550 Ma. Distinct 207Pb/206Pb age populations occur at ca. 1,302±37, 1,191±27 and 802±57 Ma, which respectively correlate with the intrusion of the Maningkorrirr/Mudginberri
phonolitic dykes and the Derim Derim Dolerite between 1,370 and 1,316 Ma, the amalgamation of Australia and Laurentia during
the Grenville Orogen at ca. 1,140 Ma, and the break-up of Rodinia between 1,000 and 750 Ma. 相似文献
THE CAPITALIST SPACE ECONOMY: Geographical Analysis after Ricardo, Marx and Sraffa by E. Sheppard and T. J. Barnes. 15 × 22 cm, xviii and 328 pages. Unwin Hyman: London 1990 (ISBN 004 330401 X) £40.00 hard; (ISBN 004 330402 8) £14.95 (soft).
THE INTERNATIONAL STEEL INDUSTRY: Restructuring, State Policies and Localities by R. Hudson and D. Sadler. 14 × 22 cm, xii and 163 pages. Routledge: London 1989 (ISBN 0 415 02186 3) $A89.95 (hard).
INDUSTRIAL TRANSFORMATION AND CHALLENGE IN AUSTRALIA AND CANADA (Carleton Library No. 164) edited by R. Hayter and P. D. White. 15 × 23 cm, x and 340 pages. Carleton University Press: Ottawa 1990 (ISBN 0 88629 129 1) $A34.95 (hard); (ISBN 0 88629 128 3) $A 19.95 (soft).
LABOUR MIGRATION. The Internal Geographical Mobility of Labour in the Developed World edited by J. H. Johnson and J. Salt. 15 × 24 cm, viii and 215 pages. David Fulton: London 1990 (ISBN 1 85346 120 2) £30.00 (hard).
CITIES IN SPACE: CITY AS PLACE by D. Herbert and C. Thomas. 15 × 23 cm, xi and 340 pages. David Fulton: London 1990 (ISBN 1 85346 138 5) £35.00 (hard); (ISBN 1 85346 109 1) £14.95 (soft).
THE NEW URBAN FRONTIER. Urbanisation and City Building in Australasia and the American West by L. Frost. 15 × 23 cm, xvii and 226 pages. New South Wales University Press: Sydney (ISBN 0 86840 268 0) $A24.95 (soft).
SYDNEY: A Social Atlas by R. Horvath, G. E. Harrison and R. M. Dowling. 19 × 28 cm, 110 pages. Sydney University Press: Sydney 1989 (ISBN 0 424 00144 6) $A19.95 (soft).
CHANGE AND ADJUSTMENT IN NORTHERN NEW SOUTH WALES edited by D. J. Walmsley. 17 × 23 cm. 118 pages. Department of Geography and Planning, University of New England: Armidale 1990 (ISBN 0 85834 887 X) $A10.00 (soft).
ANNOTATED BIBLIOGRAPHY OF URANIUM IN AUSTRALIA (Cover Title: URANIUM IN AUSTRALIA 1970–1987: An Annotated Bibliography) by C. O'Faircheallaigh, A. Webb and D. Wade‐Marshall. 18 × 25 cm, xi and 306 pages. North Australia Research Unit, Australian National University: Darwin 1989 (ISBN 07315 05433). 相似文献
On November 28, 2003, at about 00:30 PST, 35 km east of Prince Rupert in northwestern British Columbia, an extremely rapid, retrogressive liquefaction earth flow, or a clay flow-slide, severed the natural gas pipeline. As a result, Prince Rupert residents were without natural gas heat for 10 days. The landslide has a steep main scarp that is 45 m high by 345 m wide. It consists of glaciomarine sediments mantled by rubbly colluvium lying on, and against smooth bedrock of the valley wall. It covers an area of 32 ha, and displaced about 4.7 M m3 of material. This displaced material flowed up and down river over a distance of 1.7 km, blocked the river, and caused flooding upstream for a distance of 10 km. This landslide is the most recent of four large landslides that have occurred over the last four decades in glaciomarine sediments in northwestern British Columbia. 相似文献
The impact of relative sea-level rise (RSLR), damage to and possible responses in the Ebro Delta (NW Mediterranean) has been analyzed. Impact was determined by delineating delta areas prone to flooding under different RSLR scenarios. The surface areas of the different habitats were then quantified for flooding impact and affected ecosystems were assessed. The obtained results enabled us to characterize the Ebro Delta as a coastal environment that is highly sensitive to changes in sea level, with affected flooded areas likely to range between about 45 and 60 % for different RSLR scenarios, from which about 26 % would be inundated by subsidence only. In absolute terms, the habitat most likely to be affected by flooding was cropland. In relative terms, the most affected habitats were those typical of the lowest areas: saltwater wetlands, riparian buffer and areas of saline vegetation. Under present deltaic evolution with no sediment supply, adaptation is considered a plausible option for managing the Ebro delta under a RSLR scenario. This implies permitting surface area losses or land use changes in the lower parts of the delta, where natural values will be reinforced, and concentrating agriculture in the higher parts of the deltaic plain. 相似文献
Driven by a need for increased accuracy in real-time Earth orientation parameters (EOPs), the Bulletin A (Rapid Servce and
Predictions) of the International Earth Rotation Service (IERS) has recently made several major changes to its combination
and prediction procedures. Changes to the process ob combining multi-technique results include creation of a daily Bulletin
A updata, inclusion of several new data sets, and use of polar motion rantes for the latest epoch. Notably, the contributions
from GPS observations have grown steadily in significance, both for polar motion and Universal Time (UT1). The prediction
procedure has, in turn, benefited from these changes as well as improvements to the polar motion prediction model. As a result,
demanding real-time applications, such as for satellite orbit extrapolations should observe a major improvement in the accuracy
of our real-time EOP products. All results, together with supporting and diagnostic information, are available at the website
http://maia.usno.navy.mil.
The maximum EOP errors (root-mean-squared sense) that a real-time user would experience using the latest available update
of Bulletin A are currently estimated to be ∼0.9 milliarcseconds (mas) for polar motion and ∼0.15 milliseconds (ms) for UT1-UTC.
The data latency (the lag since the most recent observations) for EOP predictions need not exceed ∼41 hours for users who
avail themselves of the daily updates. Over the past four years, the accuracy for real-time applications has improved by nearly
a factor of 4 in polar motion and a factor of 10 in UT1. This is primarily due to the large reduction in data latency, which
in turn is mostly possible due to the Rapid product delivery of the International GPS Service (IGS) (see Mireault et al, 1999).
? 2001 John Wiley & Sons, Inc. 相似文献