Recent radar measurements of turbulence and microphysical parameters in marine boundary layer clouds     

A. B. White  C. W. Fairall  A. S. Frisch  B. W. Orr  J. B. Snider 《Atmospheric Research》1996,40(2-4)

We present a collection of research related to radar measurements of turbulence and microphysical properties in clouds. The radars used in these studies operate at frequencies ranging from 404 MHz to 34.6 GHz. We discuss the relative contributions made by the two primary radar scattering mechanisms to the measured values of radar reflectivity at the different frequencies. The desired turbulence and microphysical information is obtained from the radar reflectivity and other elements of the Doppler velocity spectra. Methods and examples are given with emphasis on liquid water clouds associated with the marine boundary layer.  相似文献   

Uptake and elimination of lindane and a phthalate ester in tropical corals and mussels     

J.E Solbakken  A.H Knap  P.L Orr 《Marine environmental research》1985,16(2):103-113

Phthalate esters and γ-hexachlorocyclohexane are among the organic xenobiotics which are most abundant in the atmospheric fallout over Bermuda. It was therefore of interest to study the uptake and elimination of these synthetic components in the most important reef building coral. Diploria strigosa and the mussel Arca zebra, from Bermudian waters. Radioactive labelled components (¹⁴C-γ-hexachlorocyclohexane, diisononyl [carboxyl-¹⁴C] phthalate) were used in the study and the samples were analyzed by liquid scintillation counting.The highest concentrations of radioactivity were found in hepatopancreas and more phthalate ester than lindane was taken up. In gill, muscle and coral tissues the uptake of lindane was higher than that of the phthalate ester. In all tissues analyzed the elimination rate of lindane was higher than that of the phthalate ester.The acute effects of phthalate esters on corals are probably less than those of lindane, due to the low uptake and low toxicity. However, the poor elimination of phthalate esters may lead to long-term effects.  相似文献   

Rootless shield and perched lava pond collapses at Kīlauea Volcano,Hawai'i     

Matthew R. Patrick  Tim R. Orr 《Bulletin of Volcanology》2012,74(1):67-78

Effusion rate is a primary measurement used to judge the expected advance rate, length, and hazard potential of lava flows. At basaltic volcanoes, the rapid draining of lava stored in rootless shields and perched ponds can produce lava flows with much higher local effusion rates and advance velocities than would be expected based on the effusion rate at the vent. For several months in 2007–2008, lava stored in a series of perched ponds and rootless shields on Kīlauea Volcano, Hawai'i, was released episodically to produce fast-moving 'a'ā lava flows. Several of these lava flows approached Royal Gardens subdivision and threatened the safety of remaining residents. Using time-lapse image measurements, we show that the initial time-averaged discharge rate for one collapse-triggered lava flow was approximately eight times greater than the effusion rate at the vent. Though short-lived, the collapse-triggered 'a'ā lava flows had average advance rates approximately 45 times greater than that of the pāhoehoe flow field from which they were sourced. The high advance rates of the collapse-triggered lava flows demonstrates that recognition of lava accumulating in ponds and shields, which may be stored in a cryptic manner, is vital for accurately assessing short-term hazards at basaltic volcanoes.  相似文献   

River temperature regimes of England and Wales: spatial patterns,inter‐annual variability and climatic sensitivity          下载免费PDF全文

Grace Garner  David M. Hannah  Jonathan P. Sadler  Harriet G. Orr 《水文研究》2014,28(22):5583-5598

Identification of the most sensitive hydrological regions to a changing climate is essential to target adaptive management strategies. This study presents a quantitative assessment of spatial patterns, inter‐annual variability and climatic sensitivity of the shape (form) and magnitude (size) of annual river/stream water temperature regimes across England and Wales. Classification of long‐term average (1989–2006) annual river (air) temperature regime dynamics at 88 (38) stations within England and Wales identified spatially differentiable regions. Emergent river temperature regions were used to structure detailed hydroclimatological analyses of a subset of 38 paired river and air temperature stations. The shape and magnitude of air and water temperature regimes were classified for individual station‐years; and a sensitivity index (SI, based on conditional probability) was used to quantify the strength of associations between river and air temperature regimes. The nature and strength of air–river temperature regime links differed between regions. River basin properties considered to be static over the timescale of the study were used to infer modification of air–river temperature links by basin hydrological processes. The strongest links were observed in regions where groundwater contributions to runoff (estimated by basin permeability) were smallest and water exposure time to the atmosphere (estimated by basin area) was greatest. These findings provide a new large‐scale perspective on the hydroclimatological controls driving river thermal dynamics and, thus, yield a scientific basis for informed management and regulatory decisions concerning river temperature within England and Wales. © 2013 The Authors. Hydrological Processes published by John Wiley & Sons, Ltd.  相似文献   

On the role of mesoscale eddies in the ventilation of Antarctic intermediate water     

Zouhair Lachkar  James C. Orr  Jean-Claude Dutay  Pascale Delecluse 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(6):909-925

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Skill assessment of three earth system models with common marine biogeochemistry   总被引：1，自引：0，他引：1  

Roland Séférian  Laurent Bopp  Marion Gehlen  James C. Orr  Christian Ethé  Patricia Cadule  Olivier Aumont  David Salas y Mélia  Aurore Voldoire  Gurvan Madec 《Climate Dynamics》2013,40(9-10):2549-2573

We have assessed the ability of a common ocean biogeochemical model, PISCES, to match relevant modern data fields across a range of ocean circulation fields from three distinct Earth system models: IPSL-CM4-LOOP, IPSL-CM5A-LR and CNRM-CM5.1. The first of these Earth system models has contributed to the IPCC 4th assessment report, while the latter two are contributing to the ongoing IPCC 5th assessment report. These models differ with respect to their atmospheric component, ocean subgrid-scale physics and resolution. The simulated vertical distribution of biogeochemical tracers suffer from biases in ocean circulation and a poor representation of the sinking fluxes of matter. Nevertheless, differences between upper and deep ocean model skills significantly point to changes in the underlying model representations of ocean circulation. IPSL-CM5A-LR and CNRM-CM5.1 poorly represent deep-ocean circulation compared to IPSL-CM4-LOOP degrading the vertical distribution of biogeochemical tracers. However, their representations of surface wind, wind stress, mixed-layer depth and geostrophic circulations (e.g., Antarctic Circumpolar Current) have been improved compared to IPSL-CM4-LOOP. These improvements result in a better representation of large-scale structure of biogeochemical fields in the upper ocean. In particular, a deepening of 20–40 m of the summer mixed-layer depth allows to capture the 0–0.5 μgChl L^?1 concentrations class of surface chlorophyll in the Southern Ocean. Further improvements in the representation of the ocean mixed-layer and deep-ocean ventilation are needed for the next generations of models development to better simulate marine biogeochemistry. In order to better constrain ocean dynamics, we suggest that biogeochemical or passive tracer modules should be used routinely for both model development and model intercomparisons.  相似文献   

Range finding of Alfvén oscillations and direction finding of ion-cyclotron waves by using the ground-based ULF finder     

A. Guglielmi  J. Kangas  D. Milling  D. Orr  O. Pokhotelov 《Annales Geophysicae》1997,15(4):424-429

A new approach to the problem of direction and distance finding of magnetospheric ULF oscillations is described. It is based on additional information about the structure of geoelectromagnetic field at the Earths surface which is contained in the known relations of the theory of magnetovariation and magnetotelluric sounding. This allows us to widen the range of diagnostic tools by using observations of Alfvén oscillations in the PC 3–5 frequency band and the ion-cyclotron waves in the PC 1 frequency band. Preliminary results of the remote sensing of the magnetosphere at low-latitudes using the MHD ranger technique are presented. The prospects for remote sensing of the plasmapause position are discussed.  相似文献   

Episodic Late Palaeozoic to Cenozoic denudation of the southeastern highlands of Australia: Evidence from the Bogong High Plains,Victoria     

P. B. O'Sullivan  M. Orr  A. J. O'Sullivan  A. J. W. Gleadow 《Australian Journal of Earth Sciences》2013,60(2):199-216

The Bogong High Plains of eastern Victoria occur as plateau remnants in a highly dissected region of the Australian Alps. Results from apatite fission track analyses indicate that the Bogong region experienced multiple episodes of rapid low‐temperature cooling, most of which can be tentatively linked to a tectonic cause. Early episodes of cooling occurred during the Middle to Late Devonian (ca 400–370 Ma) and Late Carboniferous to Early Permian (ca 310–290 Ma), presumably during different stages of deformation associated with the development of the Lachlan Fold Belt and glacial erosion. Rapid cooling occurred during the Late Permian to Early Triassic (ca 260–240 Ma), presumably in response to the Hunter‐Bowen orogenic event along the eastern Australian continental margin. Since the Triassic, two major episodes of fault reactivation have further displaced fission track ages between sample groups on different structural blocks. The first episode occurred during the middle Cretaceous at ca 110–90 Ma, probably in response to initial extension and denudation along the eastern Australian passive margin prior to breakup. Subsequently during the Early to mid‐Tertiary at ca 65–45 Ma, large‐scale fault reactivation occurred along the Kiewa Fault, possibly in response to changes in intraplate stresses which occurred during the middle Tertiary.  相似文献   

Groundwater levels,climate and anthropogenic factors affect the hydrology and water quality of an intermittent and a regulated subtropical stream     

Donghwan Kim  Jing Lu  Melanie E. Roberts  David T. Roberts  David N. Orr  David P. Hamilton 《水文研究》2024,38(1):e15074

Stream hydrology and water quality are highly interconnected and impacted by climate, land use and geology. We examined this connection using monitoring data from 2000 to 2019 for two streams with contrasting hydrological regimes—intermittent and regulated perennial—in subtropical Queensland, Australia. Our main objective was to evaluate relationships between groundwater levels, climate and flow regulation on the hydrology and water quality of an intermittent and a regulated subtropical stream. In intermittently flowing Lockyer Creek, flow was highly dependent on groundwater levels and occurred when the aquifer was recharged to elevations exceeding the upper 90-percentile value. With 9.4% of the catchment area in irrigated horticulture, flow in Lockyer Creek was also likely to be reduced by drawdown of the aquifer for irrigation, with no flow for 30% to 81% of days over the observation period for stations in Lockyer Creek. In contrast, flow in the mid-Brisbane River was continuous, regulated by discharge from a large upstream dam. Nutrient and suspended sediment concentrations in Lockyer Creek were generally higher than in the mid-Brisbane River, likely associated with runoff from agricultural areas adjacent to the stream, while the upstream dam likely reduced the concentration and variability of nutrients and suspended sediment in the mid-Brisbane River. During periods of low flow in the mid-Brisbane River, longitudinal changes in nutrient and suspended sediment concentrations occurred, notably a significant decrease in total and dissolved inorganic nitrogen concentrations downstream (p < 0.05), indicating a possible effect of in-stream algal uptake and denitrification. This study highlights the impact of human modifications on stream hydrology and water quality in the face of climate change. The findings can inform decision-making on groundwater irrigation or dam release control for water security.  相似文献   

Selection of characteristic values and partial factors in geotechnical designs to Eurocode 7   总被引：1，自引：0，他引：1  

Trevor L. L. Orr 《Computers and Geotechnics》2000,26(3-4):263-279

The means by which reliability is achieved in designs to ENV 1997-1, the new CEN limit state prestandard for geotechnical design, is presented. In particular, the selection of characteristic strength values and partial factors is examined. A rational method is described for selecting characteristic strength values from limited test results and experience. The reason for three cases, with different partial factors, is explained. The example of an eccentrically loaded foundation illustrates how the controlling case may depend on the loading condition. The importance of using a geometrical factor in the design of an embedded retaining wall is demonstrated.  相似文献