Sensitivity of an ecological model to soil moisture simulations from two different hydrological models   总被引：1，自引：0，他引：1  

D. Ren  L. M. Leslie  D. J. Karoly 《Meteorology and Atmospheric Physics》2008,100(1-4):87-99

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A new ice sheet model validated by remote sensing of the Greenland ice sheet     

Diandong Ren  Rong Fu  David J. Karoly  Lance M. Leslie  Jianli Chen  Clark R. Wilson 《Central European Journal of Geosciences》2010,2(4):501-513

Accurate prediction of future sea level rise requires models that accurately reproduce and explain the recent observed dramatic ice sheet behaviours. This study presents a new multi-phase, multiple-rheology, scalable and extensible geofluid model of the Greenland ice sheet that shows the credential of successfully reproducing the mass loss rate derived from the Gravity Recovery and Climate Experiment (GRACE), and the microwave remote sensed surface melt area over the past decade. Model simulated early 21st century surface ice flow compares satisfactorily with InSAR measurements. Accurate simulation of the three metrics simultaneously cannot be explained by fortunate model tuning and give us confidence in using this modelling system for projection of the future fate of Greenland Ice Sheet (GrIS). Based on this fully adaptable three dimensional, thermo-mechanically coupled prognostic ice model, we examined the flow sensitivity to granular basal sliding, and further identified that this leads to a positive feedback contributing to enhanced mass loss in a future warming climate. The rheological properties of ice depend sensitively on its temperature, thus we further verified modelâ?s temperature solver against in situ observations. Driven by the NCEP/NCAR reanalysis atmospheric parameters, the ice model simulated GrIS mass loss rate compares favourably with that derived from the GRACE measurements, or about ?147 km³/yr over the 2002–2008 period. Increase of the summer maximum melt area extent (SME) is indicative of expansion of the ablation zone. The modeled SME from year 1979 to 2006 compares well with the cross-polarized gradient ratio method (XPGR) observed melt area in terms of annual variabilities. A high correlation of 0.88 is found between the two time series. In the 30-year model simulation series, the surface melt exhibited large inter-annual and decadal variability, years 2002, 2005 and 2007 being three significant recent melt episodes.  相似文献   

ENVIRONMENTAL DISRUPTION AND ITS MECHANISM IN EAST-CENTRAL EUROPE*     

Leslie Dienes 《The Professional geographer》1974,26(4):375-381

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Lance M. Leslie  Greg J. Holland  Peter J. Webster 《Meteorology and Atmospheric Physics》1995,56(1-2):1

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Amino acid geochemistry of fossil bones from the Rancho La Brea asphalt deposit,California     

Mark A.S. McMenamin  David J. Blunt  Keith A. Kvenvolden  Scott E. Miller  Leslie F. Marcus  Richard R. Pardi 《Quaternary Research》1982,18(2):174-183

Low aspartic acid d:l ratios and modern collagenlike concentration values indicate that amino acids in bones from the Rancho La Brea asphalt deposit, Los Angeles, California are better preserved than amino acids in bones of equivalent age that have not been preserved in asphalt. Amino acids were recovered from 10 Rancho La Brea bone samples which range in age from less than 200 to greater than 36,000 yr. The calibrated rates of aspartic acid racemization range from 2.1 to 5.0 × 10^?6yr^?1. Although this wide range of rate constants decreases the level of confidence for age estimates, use of the larger rate constant of 5.0 × 10^?6yr^?1 provides minimum age estimates which fit the known stratigraphic and chronologic records of the Rancho La Brea deposits.  相似文献   

Solidus and subsolidus compositional relationships of some coexisting Skaergaard pyroxenes     

Leslie C. Coleman 《Contributions to Mineralogy and Petrology》1978,66(3):221-227

Electron-microprobe analyses of coexisting Ca-rich and Ca-poor pyroxenes from rocks of the Skaergaard intrusion indicate that their compositional relationships are controlled by two types of tie-line in the pyroxene quadrilateral. Solidus tie-lines join bulk compositions of pairs of pyroxenes that crystallized contemporaneously from a melt at equilibrium. Subsolidus tie-lines join the compositions of lamellae and host materials in pyroxene exsolution intergrowths. The solidus tie-line for a pair of pyroxenes in a specimen and their subsolidus tie-lines do not coincide and the subsolidus tie-line for inverted pigeonite is further from the hedenbergite-ferrosilite join of the quadrilateral than that for augite.The orientation of solidus tie-lines within the pyroxene quadrilateral indicates that during the simultaneous crystallization of two pyroxenes from the Skaergaard magma there was similar partitioning of Mg and Fe in the two phases relative to the melt. The relationship of the subsolidus tie-lines of a pair of coexisting pyroxenes to their solidus tie-line indicates that during the formation of exsolution intergrowths, changes in the composition of the pyroxene matrix involved primarily a change in its CaMg+Fe ratio while those of the lamellae involved both a change in their CaMg+Fe ratio and in their MgFe ratio. The MgFe ratio of the augite lamellae in inverted pigeonite progressively increased with cooling while that of the Ca-poor lamellae in augite progressively decreased with cooling.  相似文献   

The effects of bushfires on hydrological processes using a paired-catchment analysis     

S. Liu  L. M. Leslie  M. Speer  R. Bunker  X. Mo 《Meteorology and Atmospheric Physics》2004,86(1-2):31-44

Summary Several problems associated with capturing the effects of bushfires on hydrological processes in the Goulburn River catchment (6810km²), Hunter Valley, Australia are investigated using a paired-catchment analysis. It is suggested, first, that the within-year-missing data, as defined in this paper, need to be examined carefully when using the double-mass curve of annual total discharge in a paired-catchment analysis. Second, in order to provide an accurate precipitation background, which is one of the most important prerequisites for a paired-catchment analysis, the use of annual average precipitation is strongly recommended together with annual total precipitation when there are large amounts of within-year-missing data. Third, caution is needed in comparing multi-year average precipitation and streamflow data before and after the fire when the data series is not statistically long enough, since the average values for precipitation and streamflow over a different number of years may produce completely contrasting results. Fourth, the analysis of the flow duration curve, which is another useful technique in paired-catchment analysis, needs to be interpreted from the precipitation duration curve. This is because the change of flow duration curve can be caused either from the change of precipitation or the fire. Fifth, the change in streamflow, calculated by subtracting the average streamflow for the non-fire years from the observed streamflow for the years in which fires occurred, is not an efficient way of capturing the fire effects. The problem associated with this approach is not just that the streamflow is strongly dependent on rainfall, as reported elsewhere, but also, it can lead to misinterpretation using the hydrograph when the average streamflow in non-fire years is close to the average streamflow in fire years.By taking into account the above problems there was no effect of fires found on streamflow in the Goulburn River catchment. This result contrasts with the conclusions reported from other studies that have reported an immediate increase in streamflow by experimental analyses, paired-catchment analyses or modelling studies. Instead, it is shown that the spatial pattern of precipitation over the Goulburn River catchment is more important in shaping the hydrograph than the effects of bushfires. The ratio of fire extent to catchment area is approximately 4% in this study, which we suggest is a minimum area required to identify a hydrological response to the fires. The fact that other studies have focused more on capturing the generally expected effect of an immediate increase in streamflow after fire, than on why this effect occurs, makes it highly desirable to undertake micro-meteorological experiments to obtain observed evapotranspiration data before and after fire. Also, it is important to develop a coupled soil-vegetation-atmosphere-transfer dynamic mechanism and high resolution numerical weather prediction model with a distributed hydrological model in order to simulate more realistically the effect of fire on hydrological processes.  相似文献   

Correlation and dating of Quaternary alluvial-fan surfaces using scarp diffusion     

Leslie Hsu  Jon D. Pelletier 《Geomorphology》2004,60(3-4):319-335

Great interest has recently been focused on dating and interpreting alluvial-fan surfaces. As a complement to the radiometric methods often used for surface-exposure dating, this paper illustrates a rapid method for correlating and dating fan surfaces using the cross-sectional shape of gullies incised into fan surfaces. The method applies a linear hillslope-diffusion model to invert for the diffusivity age, κt (m²), using an elevation profile or gradient (slope) profile. Gullies near the distal end of fan surfaces are assumed to form quickly following fan entrenchment. Scarps adjacent to these gullies provide a measure of age. The method is illustrated on fan surfaces with ages of approximately 10 ka to 1.2 Ma in the arid southwestern United States. Two areas of focus are Death Valley, California, and the Ajo Mountains piedmont, Arizona. Gully-profile morphology is measured in two ways: by photometrically derived gradient (slope) profiles and by ground-surveyed elevation profiles. The κt values determined using ground-surveyed profiles are more consistent than those determined using photo-derived κt values. However, the mean κt values of both methods are comparable. The photometric method provides an efficient way to quantitatively and objectively correlate and relatively-date alluvial-fan surfaces. The κt values for each surface are determined to approximately 30–50% accuracy.  相似文献   

Tidally phased emergence events in a strongly tidal estuary     

Leslie H. Taylor  Shawn M. Shellito  Heather U. Abello  Peter A. Jumars 《Estuaries and Coasts》2005,28(4):500-509

Acoustic backscatter from an active sonar system over a range of six frequencies between 265 kHz and 3 MHz in the tidally dominated Damariscotta River estuary, Maine, United States, revealed that the major emergence event of the night commenced on the first tidal deceleration after dark (3.5–4 h after local slack), irrespective of flow direction. Emergence traps identified the mysid shrimp,Neomysis americana, as the dominant migrator. Water-column-integrated, acoustically estimated biovolume at our 10-m deep study location increased by a factor of about 6 during these large events, entirely dominating the holoplanktonic contribution and likely being a major component in benthic-pelagic coupling. Application of the same algorithm used to locate this nighttime emergence revealed a parallel but considerably smaller daytime emergence event near the same phase of the tide. Daytime trap samples failed to recover the organisms responsible, but transmissometry rejected the alternative hypothesis that we observed resuspension events. We suspect, but have yet only weak evidence, that animals emerging in daylight are copepods rather than mysids.  相似文献   

The Consumer Society and the Postmodern City by David B Clarke     

Deborah Leslie 《Area》2006,38(2):221-222

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