Present and future prolonged drought impacts on a large temperate embayment: Port Phillip Bay, Australia   总被引：1，自引：0，他引：1  

Randall S. Lee  Kerry P. Black  Cyprien Bosserel  Dougal Greer 《Ocean Dynamics》2012,62(6):907-922

Observations of a large temperate embayment in Victoria, Australia, reveal a sustained climatic shift that occurred in response to a prolonged drought in the region during 1997–2009. Historically, the bay is fresher than the ocean with fresh outflow to the sea. However, the drought has caused substantially elevated salinity and temperatures above adjacent oceanic waters. The bay's capacity to dilute and flush waste discharges to the ocean was also changed. Observed conditions have been numerically modelled with hydrodynamic and coupled lagrangian particle dispersion models to test differences in dispersion and exchange during historically fresher conditions and hypersaline bay scenarios. Further scenarios were tested for projected climate conditions which were similar to the recent drought responses in the bay. The models identified the effects on the circulation of the climatic shift including regions of increased vulnerability to extreme salinity in the bay, with some existing discharges concentrating in these regions of heightened vulnerability. Absolute salinity in the bay could reach critical levels of over 38?g?kg^?1, in places, which may compromise bay ecology.  相似文献   

The NOAA Goes-12 Solar X-Ray Imager (SXI) 1. Instrument, Operations, and Data     

S. M. Hill  V. J. Pizzo  C. C. Balch  D. A. Biesecker  P. Bornmann  E. Hildner  L. D. Lewis  R. N. Grubb  M. P. Husler  K. Prendergast  J. Vickroy  S. Greer  T. Defoor  D. C. Wilkinson  R. Hooker  P. Mulligan  E. Chipman  H. Bysal  J. P. Douglas  R. Reynolds  J. M. Davis  K. S. Wallace  K. Russell  K. Freestone  D. Bagdigian  T. Page  S. Kerns  R. Hoffman  S. A. Cauffman  M. A. Davis  R. Studer  F. E. Berthiaume  T. T. Saha  G. D. Berthiume  H. Farthing  F. Zimmermann 《Solar physics》2005,226(2):255-281

The Solar X-ray Imager (SXI) was launched 23 July 2001 on NOAAs GOES-12 satellite and completed post-launch testing 20 December 2001. Beginning 22 January 2003 it has provided nearly uninterrupted, full-disk, soft X-ray solar images, with a continuous frame rate significantly exceeding that for previous similar instruments. The SXI provides images with a 1 min cadence and a single-image (adjustable) dynamic range near 100. A set of metallic thin-film filters provides temperature discrimination in the 0.6 – 6.0 nm bandpass. The spatial resolution of approximately 10 arcsec FWHM is sampled with 5 arcsec pixels. Three instrument degradations have occurred since launch, two affecting entrance filters and one affecting the detector high-voltage system. This work presents the SXI instrument, its operations, and its data processing, including the impacts of the instrument degradations. A companion paper (Pizzo et al., this issue) presents SXI performance prior to an instrument degradation that occurred on 5 November 2003 and thus applies to more than 420000 soft X-ray images of the Sun.  相似文献   

MONITORING GEOMORPHOLOGICAL DISTURBANCE AND RECOVERY IN COMMERCIALLY LOGGED TROPICAL FOREST, SABAH, EAST MALAYSIA, AND IMPLICATIONS FOR MANAGEMENT     

Tony Greer  Ian Douglas  Kawi Bidin  Waidi Shun  Jadda Suhaimi 《Singapore journal of tropical geography》1996,16(1):1-21

Resource development in the form of cyclical commercial logging activities results in a short period of often severe land disturbance followed by a prolonged phase of recovery. The monitoring of catchment sediment yield gives some indication of the gross erosion processes within the catchment as a result of the disturbance and may also effectively measure any ameliorative processes. Studies in Ulu Segama, Sabah, East Malaysia, recorded significant increases in stream suspended sediment loads as a result of logging. Stream loads were derived from a combination of daily sample measurements and storm event sampling using automated liquid samplers. Measured loads were then compared to computed loads from sediment discharge rating sets derived from the actual samples. Application of these ratings in the disturbed catchment initially underestimated sediment loads; however, a progressive overestimation of loads occurred as the catchment vegetation recovered. When using sediment rating curves as a tool to measure catchment erosion rates in disturbed environments, considerable caution has to be used. Vegetation recovery is reflected in the rapid recovery of stream water quality, making it necessary to continually review the rating.  相似文献   

The excitation of the 557.7 nm line and Herzberg bands in the nightglow     

L. Thomas  R.G.H. Greer  P.H.G. Dickinson 《Planetary and Space Science》1979,27(7):925-931

Measurements of the emission intensities of the 557.7 nm line and Herzberg bands and of O(³P) concentrations carried out on two coordinated rocket flights at South Uist during the night of 8/9 September 1975 are presented. An examination of the 557.7 nm emission and $\text{O}\text{(}{}^3\text{P}\text{)}$ data on the basis of recent data on relevant rate coefficients has shown that the results can be interpreted on the basis of the Barth mechanism for the production of $\text{O}\text{(}{}^1\text{S}\text{)}$ atoms but not the Chapman mechanism. Evidence is provided that the A³Σ⁺_u state of O₂ could be responsible for the $\text{O}\text{(}{}^1\text{S}\text{)}$ production in the Barth mechanism. Values of the rate coefficients involved are deduced from a comparison of the 557.7 nm and Herzberg emission rates.  相似文献   

The movements of plaice (Pleuronectes platessa L.) tracked in the open sea     

Walker  M. Greer; Jones  F. R. Harden; Arnold  G. P. 《ICES Journal of Marine Science》1978,38(1):58-86

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Effect of Starvation and Exercise on the Skeletal Muscle Fibres of the Cod (Gadus Morhua L.) and the Coalfish (Gadus Virens L.) Respectively     

Walker  M. Greer 《ICES Journal of Marine Science》1971,33(3):421-427

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A rocket-borne photometric investigation of the oxygen lines at 5577 Å and 6300 Å, the sodium D-lines and the continuum at 5300 Å in the night airglow     

R. G. H. Greer  G. T. Best 《Planetary and Space Science》1967,15(12):1857-1881

The relative variations between 82 km and 205 km in the emission rates of nightglow radiation features at 5300 Å, 5577 Å, 5893 Å and 6300 Å have been photometrically measured from a Skylark rocket flown from Woomera, S. Australia at 2053 hours CST (1123 hours GMT) on 18 October, 1965.

Emission profiles obtained for the first three features show that these layers have their centre of intensity at, respectively, 94.0 ± 1 km, 94.5 ± 0.5, and 98.0 ± 2 km. The results further indicate that not more than 10% of the 6300 Å radiation was emitted below apogee at 205 km.

By virtue of a rather complicated vehicle motion—almost a slow tumble in the vertical plane—evidence is adduced which suggests that differences between these profiles and those of previous flights could be explained by insufficient or incorrect account being then taken of the contamination from extra-atmospheric sources such as starlight and galactic light.

Regarding the continuum, it is found that, depending on the particular region of sky background, up to 80% of the 5300 Å emission observed from the Earth may be extra-atmospheric in origin. Furthermore, of the extra-atmospheric component, again depending on the viewing direction in the sky, the emission intensity at 5577 Å may be from 10% to 50% greater than that at 5300 Å.

While it is to be expected that, before penetrating the layer, the zenithal emission intensity as registered by the photometers should remain constant, this constancy was not generally observed and the 5300 Å and 5577 Å photometers, both of which were independently duplicated, indicate an initial increasing emission intensity. Marked differences in the variation of each pair of photometers suggest that interpretation by means of aerosol absorption of the radiation in the 80 to 100-km region is incorrect and that the effect is probably instrumental in origin and of a temporary nature.  相似文献   

Interpreting luminescence data from a portable OSL reader: three case studies in fluvial settings     

Esperanza Muñoz‐Salinas  Paul Bishop  David CW Sanderson  Jose‐Juan Zamorano 《地球表面变化过程与地形》2011,36(5):651-660

Optically stimulated luminescence (OSL) is a technique that has been applied from the mid‐1980s, mainly for sediment dating. The OSL technique is based on sample stimulation by light to determine the luminescence signal that is stored in the crystal lattices of sediment grains after deposition, burial by later sediment and subsequent exposure to ionizing radiation from radioactive elements in the surrounding sediment. In such sediment dating, two parameters are required: the equivalent dose (i.e. the luminescence signal stored in the grains), and the dose rate (i.e. the ionizing energy from α, β and γ radiation emitted by naturally occurring radioisotopes in the deposit, plus the effects of cosmic radiation). In this research, the OSL technique is not used for dating. The study goal is to analyse only the luminescence signals (the total photon counts) in polymineral samples obtained after light stimulation in the blue (BLSL) and infrared (IRSL) wavelengths using a portable OSL reader designed and built at the Scottish Universities Environmental Research Centre (SUERC). Three fluvial case studies – from Cambodia, Australia and Mexico – are used to illustrate the geomorphological interpretations possible with the portable OSL reader data from sediments resulting from a range of different depositional processes. The case studies show that aspects of sediment's transport and depositional processes can be inferred from the portable OSL reader data, providing valuable insights into geomorphological history. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Specific conductance–stage relationships in Appalachian valley fill streams     

Elyse V. Clark  Breeyn M. Greer  Carl E. Zipper  Erich T. Hester 《Environmental Earth Sciences》2016,75(17):1222

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Effects of mechanical macrophyte control on suspended sediment concentrations in streams     

MJC Greer  AS Hicks  SK Crow  GP Closs 《新西兰海洋与淡水研究杂志》2013,47(2):254-278

Suspended sediment (SS) is an important pollutant in freshwater ecosystems and can be detrimental to fish communities. Although macrophytes mediate sediment deposition, little effort has been put into determining how their removal affects sediment resuspension. The present study examined the immediate and long-term impacts of mechanical macrophyte removal on SS concentrations in streams. The results of this study suggest that bed disturbance during mechanical excavation of macrophytes significantly increases SS in the short term, and concentrations were found to increase by as much as 15,687 mg L^–1 immediately after macrophyte removal. Significant long-term (77 day) increases in SS were also observed, indicating that without macrophytes, disturbed material is continually resuspended after excavation by fluvial processes. These results demonstrate that macrophyte removal can result in SS levels that have previously been shown to harm fish, and indicate that this activity may be more detrimental to fish than previously thought.  相似文献