Sources of uncertainty in estimating stream solute export from headwater catchments at three sites          下载免费PDF全文

Ruth D. Yanai  Naoko Tokuchi  John L. Campbell  Mark B. Green  Eiji Matsuzaki  Stephanie N. Laseter  Cindi L. Brown  Amey S. Bailey  Pilar Lyons  Carrie R. Levine  Donald C. Buso  Gene E. Likens  Jennifer D. Knoepp  Keitaro Fukushima 《水文研究》2015,29(7):1793-1805

Uncertainty in the estimation of hydrologic export of solutes has never been fully evaluated at the scale of a small‐watershed ecosystem. We used data from the Gomadansan Experimental Forest, Japan, Hubbard Brook Experimental Forest, USA, and Coweeta Hydrologic Laboratory, USA, to evaluate many sources of uncertainty, including the precision and accuracy of measurements, selection of models, and spatial and temporal variation. Uncertainty in the analysis of stream chemistry samples was generally small but could be large in relative terms for solutes near detection limits, as is common for ammonium and phosphate in forested catchments. Instantaneous flow deviated from the theoretical curve relating height to discharge by up to 10% at Hubbard Brook, but the resulting corrections to the theoretical curve generally amounted to <0.5% of annual flows. Calibrations were limited to low flows; uncertainties at high flows were not evaluated because of the difficulties in performing calibrations during events. However, high flows likely contribute more uncertainty to annual flows because of the greater volume of water that is exported during these events. Uncertainty in catchment area was as much as 5%, based on a comparison of digital elevation maps with ground surveys. Three different interpolation methods are used at the three sites to combine periodic chemistry samples with streamflow to calculate fluxes. The three methods differed by <5% in annual export calculations for calcium, but up to 12% for nitrate exports, when applied to a stream at Hubbard Brook for 1997–2008; nitrate has higher weekly variation at this site. Natural variation was larger than most other sources of uncertainty. Specifically, coefficients of variation across streams or across years, within site, for runoff and weighted annual concentrations of calcium, magnesium, potassium, sodium, sulphate, chloride, and silicate ranged from 5 to 50% and were even higher for nitrate. Uncertainty analysis can be used to guide efforts to improve confidence in estimated stream fluxes and also to optimize design of monitoring programmes. © 2014 The Authors. Hydrological Processes published John Wiley & Sons, Ltd.  相似文献   

Erupting Magnetic Structures observed with SOHO/LASCO     

Lyons  M.A.  Simnett  G.M. 《Solar physics》2001,200(1-2):203-211

We report observations, from March 1999 to December 1999, of slow-moving, low-mass (10¹⁴ g) erupting structures. The 20 events seen in this period appear with a double or multiple loop structure. Their speeds range from approximately 10 to 60 km s^–1. There are no significant associated flares or radio signatures. Although the speed distribution of these events overlaps that of coronal mass ejections (CMEs), we propose that they are morphologically different structures and are not merely a continuation of the lower range of the CME speed distribution. The aim of this paper is to characterize these events and to emphasize the insight into general CME research that such simple phenomena could give.  相似文献   

Geochemistry of Pyramid Lake sediments: influence of anthropogenic activities and climatic variations within the basin     

Z. Yang  E. Graham  W. Lyons 《Environmental Geology》2003,43(6):688-697

In 1998, a 59-cm sediment box core (PLB98-2) was taken from the deepest part of Pyramid Lake (water depth =106 m), Nevada. Age control for PLB98-2 was provided using a variety of approaches. Dried sediment samples were leached with 10% ultra-pure nitric acid and analyzed for their elemental concentrations using standard ICP techniques. The variations in elemental concentrations can be divided into two periods: one prior to European settlement and one influenced by anthropogenic activities. The concentrations of K, Al, Na, Zn, and Mn all began to increase after pre-European manipulation of the watershed in ~1860, which indicates the increasing soil erosion in the watershed was due to deforestation and development. The highest concentrations of these elements and lithogenic elements such as P, Mg, Fe, Cu, Ba, and Si occurred during the flood event of the 1990s. The Pb enrichment times are similar to what has been observed in estuaries draining the western Sierra Nevada, but the Pb enrichments in Pyramid Lake are much less. The Ca, TOC, TIC, Sr, and Ba concentrations show a strong association that is closely related to drought-wet variations of climate and the construction of Derby Dam for water diversions in the early 1900s. Se concentrations vary with the '¹⁸O of the carbonate in the sediments. Although the '¹⁸O "leads" the other species and Truckee River discharge by a few years, it is an excellent indicator of the hydrological change of Pyramid Lake, which is related to climate changes and human activities. From ~1920, Mn and Mo vary inversely in the sediments. In general, the Mo concentrations varies directly with the organic carbon content of the sediments from 1910 to ~1980, suggesting enhanced removal of Mo during times of increased productivity in the lake, and anoxic conditions at the sediment/water interface. This coincides with low lake levels. The elemental composition of the sediments in Pyramid Lake clearly reflect the timing of important anthropogenic activities and climatic variations that have taken place within the watershed over the past 240 years.  相似文献   

Regional turbulent statistics over contrasting natural surfaces   总被引：1，自引：0，他引：1  

T. J. Lyons  Li Fuqin  J. M. Hacker  Wan-Li Cheng  Huang Xinmei 《Meteorology and Atmospheric Physics》2001,78(3-4):183-194

Summary Regional turbulent fluxes of momentum, sensible and latent heat collected over both agricultural and native vegetation in the south west of Australia are presented. Analysis of the energy spectrum illustrates that the most energetic eddies are between scales of 20 metres to 5 kilometres and highlights the spatial distance required to obtain representative regional fluxes. For the sensible heat flux, this distance is a function of measurement height whereas the latent flux is also influenced by surface variability. Statistics of these fluxes highlight that for the unstable surface layer, despite marked differences in the underlying vegetation and the corresponding sources of heat and moisture, heat is transported more efficiently than water vapour from the ground surface. Received October 9, 2000/Revised April 23, 2001  相似文献   

Windfield analysis of the Kwinana industrial region     

F. H. Kamst  Dr. T. J. Lyons  J. N. Carras 《Theoretical and Applied Climatology》1980,28(1-2):15-30

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Dissolved organic matter in pore water of carbonate sediments from Bermuda     

Wm.Berry Lyons  Henri E. Gaudette  Alan D. Hewitt 《Geochimica et cosmochimica acta》1979,43(3):433-437

Pore water samples from seven nearshore areas in Bermuda were obtained under in situ conditions and analyzed for dissolved organic carbon, dissolved carbohydrates, dissolved free amino acids and dissolved humic substances. The concentration of dissolved organic carbon is higher than in the overlying nearshore waters indicating significant diagenetic remobilization of carbon in these recently deposited carbonate sediments. Dissolved carbohydrates decrease with depth due to microbial utilization.  相似文献   

Optimized system to improve pumping rate stability during aquifer tests   总被引：1，自引：0，他引：1  

Young MH  Rasmussen TC  Lyons FC  Pennell KD 《Ground water》2002,40(6):629-637

Aquifer hydraulic properties are commonly estimated using aquifer tests, which are based on an assumption of a uniform and constant pumping rate. Substantial uncertainties in the flow rate across the borehole-formation interface can be induced by dynamic head losses, caused by rapid changes in borehole water levels early in an aquifer test. A system is presented that substantially reduces these sources of uncertainty by explicitly accounting for dynamic head losses. The system which employs commonly available components (including a datalogger, pressure transducers, a variable-speed pump motor, a flow controller, and flowmeters), is inexpensive, highly mobile, and easily set up. It optimizes the flow rate at the borehole-formation interface, making it suitable for any type of aquifer test, including constant, step, or ramped withdrawal and injection, as well as sinusoidal. The system was demonstrated for both withdrawal and injection tests in three aquifers at the Savannah River Site. No modifications to the control system were required, although a small number of characteristics of the pumping and monitoring system were added to the operating program. The pumping system provided a statistically significant, constant flow rate with time. The range in pumping variability (95% confidence interval) was from +/- 2.58 x 10(-4) L/sec to +/- 9.07 x 10(-4) L/sec, across a wide range in field and aquifer conditions.  相似文献   

Clouds prefer native vegetation   总被引：9，自引：0，他引：9  

T. J. Lyons 《Meteorology and Atmospheric Physics》2002,80(1-4):131-140

Summary The replacement of native vegetation for agriculture leads to significant changes in land surface characteristics, such as albedo, surface roughness and canopy resistance. These land surface changes induce changes in the atmospheric boundary layer. From an analysis of case studies and climatological records, it is shown that in Western Australia this change in surface characteristics and in particular, the albedo, has reduced the occurrence of convective cloud formation through limiting the vertical development of the boundary layer. Received November 14, 2001 Revised December 28, 2001  相似文献   

Historical backcasting of metal concentrations in the Chattahoochee River, Georgia: Population growth and environmental policy     

Klaus Neumann  W. Berry Lyons  Elizabeth Y. Graham  Edward Callender 《Applied Geochemistry》2005,20(12):2315-2324

The impact of increasing urbanization on the quality of a river system has been investigated by examining the current concentration of trace metals in the Chattahoochee River south of Atlanta, GA, and comparing these to previously published historical sediment data from reservoirs along the river. The lack of historical data for dissolved metal concentrations prior to 1980 requires an approach using these historic metal data from sediment cores. Core data are combined with current suspended load and dissolved metal data to “backcast” dissolved metal concentrations in the metro-Atlanta portion of the Chattahoochee River. The data suggest that the per capita input of dissolved trace metals have actually decreased since the 1920s, but anthropogenic inputs of metal are still a substantial water quality issue.  相似文献   

Arctic hazes in summer over Greenland and the North American Arctic. I: Incidence and origins     

Charles A. Brock  Lawrence F. Radke  Jamie H. Lyons  Peter V. Hobbs 《Journal of Atmospheric Chemistry》1989,9(1-3):129-148

Airborne observations during August 1985 over Greenland and the North American Arctic revealed that dense, discrete haze layers were common above 850 mb. No such hazes were found near the surface in areas remote from local sources of particles. The haze layers aloft were characterized by large light-scattering coefficients due to dry particles (maximum value 1.24 × 10^–4m^–1) and relatively high total particle concentrations (maximum value 3100 cm^–3). Sulfate was the dominant ionic component of the aerosol (0.06 – 1.9 g m^–3); carbon soot was also present. Evidence for relatively fresh aerosols, accompanied by NO₂ and O₃ depletion, was found near, but not within, the haze layers. The hazes probably derived from anthropogenic sources and/or biomass burning at midlatitudes.It is hypothesized that the scavenging of particles by stratus clouds plays an important role in reducing the frequency and intensity of hazes at the surface in the Arctic in summer. Since the detection of haze layers aloft through measurements of column-integrated parameters from the surface (e.g., by lidar) cannot be carried out reliably when clouds are present, such measurements have likely underestimated the occurrence of haze layers in the Arctic, particularly in summer.  相似文献