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211.
Wiens Ashton Kleiber William Barnhart Katherine R. Sain Dylan 《Mathematical Geosciences》2020,52(4):527-542
Mathematical Geosciences - Two common tasks when processing point cloud data sets are surface estimation and point cloud registration. In this paper, a statistical approach is developed to solve... 相似文献
212.
Desert pavement development and landscape stability on the Eastern Libyan Plateau, Egypt 总被引:1,自引:0,他引:1
Desert pavement surfaces of the eastern Libyan Plateau in central Egypt represent a stable landscape preserving Middle and Upper Paleolithic artifacts. Detailed measurements of pavement clasts indicate significant variability in clast size, density, lithology and orientation between pavements, but no spatial relationship among any of these pavement variables over the study area. Pavement characteristics are unrelated to local geomorphic features including slope gradient and aspect, suggesting a desert pavement surface that has developed without significant influence from transporting mechanisms such as overland flow and slope failure. Meridional vertical cracks in surface clasts implicate thermal stresses due to diurnal solar variation as a mechanical weathering process, whereas the presence of a clast-free silty layer within all soil profiles indicates that these are accretionary pavement surfaces that have grown upward over time. The desert pavement in this region has likely developed in situ through mechanical breakdown of surface clasts and desert pedogenesis, indicating long-term stability for this region and minimal taphonomic effects on artifacts > 2 cm in diameter deposited on this surface over the last ca. 100 ka. 相似文献
213.
Large wood distribution,mobility, and recruitment in an inter‐dam river reach: A comparison with geomorphic process on the Garrison Reach of the Missouri River pre and post the historical 2011 flood
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Edward R. Schenk Adam J. Benthem Mark D. Dixon Melissa Mittelman Katherine J. Skalak Cliff R. Hupp Joel M. Galloway Rochelle A. Nustad 《地球表面变化过程与地形》2018,43(8):1677-1688
This study assessed the effect of the largest flood since dam regulation on geomorphic and large wood (LW) trends using LW distributions at three time periods on the 150 km long Garrison Reach of the Missouri River. In 2011, a flood exceeded 4390 m3/s for a two‐week period (705% above mean flow; 500 year flood). LW was measured using high resolution satellite imagery in summer 2010 and 2012. Ancillary data including forest character, vegetation cover, lateral bank retreat, and channel capacity. Lateral bank erosion removed approximately 7400 standing trees during the flood. Other mechanisms, that could account for the other two‐thirds of the measured in‐channel LW, include overland flow through floodplains and islands. LW transport was commonly near or over 100 km as indicated by longitudinal forest and bank loss and post‐flood LW distribution. LW concentrations shift at several locations along the river, both pre‐ and post‐flood, and correspond to geomorphic river regions created by the interaction of the Garrison Dam upstream and the Oahe Dam downstream. Areas near the upstream dam experienced proportionally higher rates of bank erosion and forest loss but in‐channel LW decreased, likely due to scouring. A large amount of LW moved during this flood, the chief anchoring mechanism was not bridges or narrow channel reaches but the channel complexity of the river delta created by the downstream reservoir. Areas near the downstream dam experienced bank accretion and large amounts of LW deposition. This study confirms the results of similar work in the Reach: despite a historic flood longitudinal LW and channel trends remain the same. Dam regulation has created a geomorphic and LW pattern that is largely uninterrupted by an unprecedented dam regulation era flood. River managers may require other tools than infrequent high intensity floods to restore geomorphic and LW patterns. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
214.
Bridget Livers Katherine B. Lininger Natalie Kramer Alicia Sendrowski 《地球表面变化过程与地形》2020,45(13):3336-3353
Porosity, or void space, of large wood jams in stream systems has implications for estimating wood volumes and carbon storage, the impacts of jams on geomorphic and ecological processes, and instream habitat. Estimating porosity and jam dimensions (i.e. jam volume) in the field is a common method of measuring wood volume in jams. However, very few studies explicitly address the porosity values in jams, how porosity is calculated and assessed for accuracy, and the effect such estimates have on carbon and wood budgets in river corridors. We compare methods to estimate jam porosity and wood volume using field data from four different depositional environments in North America (jam types include small in-channel jams, large channel-margin jams, a large island apex jam, and a large coastal jam), and compare the results with previous studies. We find that visual estimates remain the most time-efficient method for porosity estimation in the field, although they appear to underpredict back-calculated porosity values; the accuracy of jam porosity, and thus wood volume, estimates are difficult to definitively measure. We also find that porosity appears to be scale invariant, dictated mostly by jam type, (which is influenced by depositional processes), rather than the size of the jam. Wood piece sorting and structural organization are likely the most influential properties on jam porosity, and these factors vary according to depositional environment. We provide a framework and conceptual model that uses these factors to demonstrate how modeled jam porosity values differ and give recommendations as a catalyst for future work on porosity of wood jams. We conclude that jam type and size and/or the study goals may dictate which porosity method is the most appropriate, and we call for greater transparency and reporting of porosity methods in future studies. © 2020 John Wiley & Sons, Ltd. 相似文献
215.
Katherine Witt Helen Ross Sylvie Shaw Natalie Jones David Rissik Breanna Pinner 《社会与自然资源》2019,32(6):638-656
In Integrated Catchment (or Watershed) Management, the impacts of upstream conditions and actions on downstream environments and people is a key issue. Knowing upstream people’s values towards waterways is, therefore, important for community engagement and the development of publicly acceptable management approaches. This qualitative study applies Kellert’s framework of relational values to explore the types and diversity of people’s values towards the upper catchments of South East Queensland, Australia, and tests the “universality” of Kellert’s framework. We found the full range of values identified by Kellert with some variations and elaborations in content. People living, working, and enjoying recreation in the upper catchments have affection for their local waterways and a moral inclination to protect them. This extends our understanding of how people value these waterways, which is more often depicted in terms of utilitarian and economic value. The findings provide managers with new opportunities for engaging with local communities and waterway users. 相似文献
216.
Ajoy Kumar Peter Minnett Guillermo Podestá Robert Evans Katherine Kilpatrick 《Journal of Earth System Science》2000,109(4):395-405
As part of the Pathfinder program developed jointly by National Aeronautics and Space Administration (NASA) and National Oceanic
and Atmospheric Administration (NOAA) a large database ofin situ sea surface temperature (SST) measurements coincident with satellite data is now available to the user community. The Pathfinder
Matchup Database (PMDB) is a multi-year, multi-satellite collection of coincident measurements from the Advanced Very High
Resolution Radiometer (AVHRR) and broadly distributed buoy data (matchups). This database allows the user community to test
and validate new SST algorithms to improve the present accuracy of surface temperature measurements from satellites. In this
paper we investigate the performance of a global Pathfinder algorithm to specific regional conditions. It is shown that for
zenith angles less than 45°, the best-expected statistical discrepancy between satellite and buoy data is about ∼ 0.5 K. In
general, the bias of the residuals (satellite — buoy) is negative in most regions, except in the North Atlantic and adjacent
seas, where the residuals are always positive. A seasonal signal in SST residuals is observed in all regions and is strongest
in the Indian Ocean. The channel-difference term used as a proxy for atmospheric water vapor correction is observed to be
unresponsive for columnar water vapor values greater than 45 mm and high zenith angles. This unresponsiveness of the channels
leads to underestimation of sea surface temperature from satellites in these conditions. 相似文献
217.
This study examined how the United States’ National Oceanic and Atmospheric Administration (NOAA) has begun to implement and change its management strategy towards one of an ecosystem approach to management (EAM). In 2005, surveys were conducted with NOAA scientists and resource managers in nine NOAA programs in eight geographic regions across the United States. We quantitatively examined temporal and spatial trends in NOAA's EAM project implementation. Through a qualitative analysis of the data, we identified important lessons learned, best practices, and challenges of NOAA EAM projects. A content analysis identified three of the most frequently provided “success strategies” and include: (1) encouraging collaborations, (2) utilizing multidisciplinary approaches, and (3) identifying common priorities among constituents. We conclude with recommendations for initiatives that NOAA, and others interested in EAM, can undertake to facilitate further ecosystem management opportunities. 相似文献
218.
An evaluation of progress in implementing ecosystem-based management of fisheries in 33 countries 总被引:1,自引:0,他引:1
Tony J. Pitcher Daniela Kalikoski Katherine Short Divya Varkey Ganapathiraju Pramod 《Marine Policy》2009
The performance of 33 countries was evaluated for ecosystem-based management (EBM) of fisheries in three fields (principles, criteria and implementation) using quantitative ordination including uncertainty. No country rated overall as ‘good’, only four countries were ‘adequate’, while over half received ‘fail’ grades. A few developing countries performed better than many developed nations. Two case studies test the method. In Indonesia, Raja Ampat and Papua, rated similar to the national evaluation, but better performance might follow successful implementation of a planned EBM initiative. A workshop in Australia rated regional fisheries managed by New South Wales 20% lower for EBM than federally managed fisheries. 相似文献
219.
Sources and fate of nutrients in a subtropical reservoir 总被引:1,自引:0,他引:1
Michele?A.?BurfordEmail author Susanne?A.?Green Andrew?J.?Cook Suzanne?A.?Johnson Jason?G.?Kerr Katherine?R.?O’Brien 《Aquatic Sciences - Research Across Boundaries》2012,74(1):179-190
This study examined the sources and fate of nutrient inputs from two principal tributaries to the eutrophic subtropical Wivenhoe
reservoir: an unregulated river and a dammed river with regular releases, during a period of declining reservoir water levels.
Nutrient budgets were constructed over a period of 6 years, and combined with short-term data on nutrient concentrations and
forms, and δ15N stable isotope data. Our study found that over a 6 year period, there was net retention of phosphorus (P) in the reservoir,
with 60% of inputs retained. Most of the P input load came from the unregulated river, with an agricultural catchment, during
periods of high flow. During one event half of the total TP load from the unregulated river in the study period was delivered
in only 12 days. Much of the P was dissolved inorganic P (DIP) and was derived from high P concentrations in soils and sediments.
This highlights the importance of appropriate catchment management practices to reduce P losses from terrestrial systems because
retention of P in reservoir sediments reduces the availability of this nutrient for agricultural production. In contrast,
there was negligible retention of nitrogen (N). The unregulated river was an important source of N derived from N fixation
in the river and adjacent soils, while the source from the dammed river was mostly reprocessed N. The high retention of P
relative to N is consistent with relatively higher accumulation of P in sediments. 相似文献
220.
Alexander Popp Steven K. Rose Katherine Calvin Detlef P. Van Vuuren Jan Phillip Dietrich Marshall Wise Elke Stehfest Florian Humpenöder Page Kyle Jasper Van Vliet Nico Bauer Hermann Lotze-Campen David Klein Elmar Kriegler 《Climatic change》2014,123(3-4):495-509
In this article, we evaluate and compare results from three integrated assessment models (GCAM, IMAGE, and ReMIND/MAgPIE) regarding the drivers and impacts of bioenergy production on the global land system. The considered model frameworks employ linked energy, economy, climate and land use modules. By the help of these linkages the direct competition of bioenergy with other energy technology options for greenhouse gas (GHG) mitigation, based on economic costs and GHG emissions from bioenergy production, has been taken into account. Our results indicate that dedicated bioenergy crops and biomass residues form a potentially important and cost-effective input into the energy system. At the same time, however, the results differ strongly in terms of deployment rates, feedstock composition and land-use and greenhouse gas implications. The current paper adds to earlier work by specific looking into model differences with respect to the land-use component that could contribute to the noted differences in results, including land cover allocation, land use constraints, energy crop yields, and non-bioenergy land mitigation options modeled. In scenarios without climate change mitigation, bioenergy cropland represents 10–18 % of total cropland by 2100 across the different models, and boosts cropland expansion at the expense of carbon richer ecosystems. Therefore, associated emissions from land-use change and agricultural intensification as a result of bio-energy use range from 14 and 113 Gt CO2-eq cumulatively through 2100. Under climate policy, bioenergy cropland increases to 24–36 % of total cropland by 2100. 相似文献