243 research outputs found
Weekly high-resolution multi-spectral and thermal uncrewed-aerial-system mapping of an alpine catchment during summer snowmelt, Niwot Ridge, Colorado
Alpine ecosystems are experiencing rapid change as a result of warming temperatures and changes in the quantity, timing and phase of precipitation. This in turn impacts patterns and processes of ecohydrologic connectivity,
vegetation productivity and water provision to downstream regions. The fine-scale heterogeneous nature of these environments makes them challenging
areas to measure with traditional instrumentation and spatiotemporally coarse satellite imagery. This paper describes the data collection,
processing, accuracy assessment and availability of a series of approximately weekly-interval uncrewed-aerial-system (UAS) surveys flown over the Niwot Ridge Long Term Ecological Research site during the 2017 summer-snowmelt season. Visible, near-infrared and thermal-infrared imagery was collected. This unique series of 5â25âcm resolution multi-spectral and thermal orthomosaics provides a unique snapshot of seasonal transitions in a high alpine catchment. Weekly radiometrically calibrated normalised
difference vegetation index maps can be used to track vegetation health at the pixel scale through time. Thermal imagery can be used to map the
movement of snowmelt across and within the near sub-surface as well as identify locations where groundwater is discharging to the surface. A 10âcm resolution digital surface model and dense point cloud (146Â pointsâmâ2) are also provided
for topographic analysis of the snow-free surface. These datasets augment ongoing data collection within this heavily studied and important
alpine site; they are made publicly available to facilitate wider use by the research community. Datasets and related metadata can be accessed through the Environmental Data Initiative Data Portal, https://doi.org/10.6073/pasta/dadd5c2e4a65c781c2371643f7ff9dc4 (Wigmore, 2022a), https://doi.org/10.6073/pasta/073a5a67ddba08ba3a24fe85c5154da7 (Wigmore, 2022c), https://doi.org/10.6073/pasta/a4f57c82ad274aa2640e0a79649290ca
(Wigmore and Niwot Ridge LTER, 2021a), https://doi.org/10.6073/pasta/444a7923deebc4b660436e76ffa3130c (Wigmore and Niwot Ridge LTER, 2021b), https://doi.org/10.6073/pasta/1289b3b41a46284d2a1c42f1b08b3807 (Wigmore and Niwot Ridge LTER, 2022a), https://doi.org/10.6073/pasta/70518d55a8d6ec95f04f2d8a0920b7b8 (Wigmore and Niwot Ridge LTER, 2022b). A summary of the available datasets can be found in the data availability section below.</p
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Case study of spatial and temporal variability of snow cover, grain size, albedo and radiative forcing in the Sierra Nevada and Rocky Mountain snowpack derived from imaging spectroscopy
Quantifying the spatial distribution and temporal change in mountain snow
cover, microphysical and optical properties is important to improve our
understanding of the local energy balance and the related snowmelt and
hydrological processes. In this paper, we analyze changes of snow cover,
optical-equivalent snow grain size (radius), snow albedo and radiative
forcing by light-absorbing impurities in snow and ice (LAISI) with respect to
terrain elevation and aspect at multiple dates during the snowmelt period.
These snow properties are derived from the NASA/JPL Airborne Visible/Infrared
Imaging Spectrometer (AVIRIS) data from 2009 in California's Sierra Nevada
and from 2011 in Colorado's Rocky Mountains, USA.
Our results show a linearly decreasing snow cover during the ablation period
in May and June in the Rocky Mountains and a snowfall-driven change in snow
cover in the Sierra Nevada between February and May. At the same time, the
snow grain size is increasing primarily at higher elevations and north-facing
slopes from 200Â microns to 800Â microns on average. We find that intense
snowmelt renders the mean grain size almost invariant with respect to
elevation and aspect. Our results confirm the inverse relationship between
snow albedo and grain size, as well as between snow albedo and radiative
forcing by LAISI. At both study sites, the mean snow albedo value decreases
from approximately 0.7 to 0.5 during the ablation period. The mean snow grain
size increased from approximately 150Â to 650Â microns. The mean radiative
forcing increases from 20âŻWâŻmâ2 up to 200âŻWâŻmâ2 during the
ablation period. The variability of snow albedo and grain size decreases in
general with the progression of the ablation period. The spatial variability
of the snow albedo and grain size decreases through the melt season while the
spatial variability of radiative forcing remains constant.</p
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Effects of Snow Water Storage on Hydrologic Partitioning Across the Mountainous, Western United States
In the montane western United States, where the majority of downstream water resources are derived from snowmelt, a warming climate threatens the timing and amount of future water availability. It is expected that the fraction of precipitation falling as snow will continue decreasing and the timing of snowmelt will continue shifting earlier in the year with unknown impacts on partitioning between evapotranspiration and streamflow. To assess this, we employ a Snow Storage Index (SSI) to represent the annual temporal phase difference between daily precipitation and daily modeled surface water inputs (SWI, the sum of rainfall and snowmelt), weighted by the respective amounts. We coupled the SSI metric with a Budyko-based framework to determine the effect of snow water storage on relative hydrologic partitioning across snow-influenced watersheds in the western U.S. Greater snow water storage was positively correlated with greater hydrologic partitioning to streamflow, particularly in the North Cascades/Cascades (r2: 0.62), Blue Mountains (r2: 0.56), Canadian Rockies (r2: 0.55), Idaho Batholith, (r2: 0.48), and Columbia Mountains/Northern Rockies (r2: 0.45). The weekly SWI:P ratio was an equally strong predictor for hydrologic partitioning, particularly in mid-spring (e.g., March/April) in the same mountainous areas (r2: 0.62–0.74, across the same eco-regions). The retention of snow water storage and subsequent release of stored water in summer months resulted in increased hydrologic partitioning to streamflow. If SSI decreases with future warming, the volume of water partitioned streamflow will decrease non-uniformly across the western U.S. with substantial implications for ecosystems and agricultural, industrial, and domestic water supplies.
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Elevation-dependent influence of snow accumulation on forest greening
Rising temperatures and declining water availability have influenced the ecological function of mountain forests over the past half-century. For instance, warming in spring and summer and shifts towards earlier snowmelt are associated with an increase in wildfire activity and tree mortality in mountain forests in the western United States(1,2). Temperature increases are expected to continue during the twenty-first century in mountain ecosystems across the globe(3,4), with uncertain consequences. Here, we examine the influence of interannual variations in snowpack accumulation on forest greenness in the Sierra Nevada Mountains, California, between 1982 and 2006. Using observational records of snow accumulation and satellite data on vegetation greenness we show that vegetation greenness increases with snow accumulation. Indeed, we show that variations in maximum snow accumulation explain over 50% of the interannual variability in peak forest greenness across the Sierra Nevada region. The extent to which snow accumulation can explain variations in greenness varies with elevation, reaching a maximum in the water-limited mid-elevations, between 2,000 and 2,600 m. In situ measurements of carbon uptake and snow accumulation along an elevational transect in the region confirm the elevation dependence of this relationship. We suggest that mid-elevation mountain forest ecosystems could prove particularly sensitive to future increases in temperature and concurrent changes in snow accumulation and melt
Beyond 'Global Production Networks': Australian Fashion Week's Trans-Sectoral Synergies
When studies of industrial organisation are informed by commodity chain, actor network, or global production network theories and focus on tracing commodity flows, social networks, or a combination of the two, they can easily overlook the less routine trans-sectoral
associations that are crucial to the creation and realisation of value. This paper shifts attention to
identifying the sites at which diverse specialisations meet to concentrate and amplify mutually reinforcing circuits of value. These valorisation processes are demonstrated in the case of Australian Fashion Week, an event in which multiple interests converge to synchronize different expressions
of fashion ideas, actively construct fashion markets and enhance the value of a diverse range of fashionable commodities. Conceptualising these interconnected industries as components of a trans-sectoral fashion complex has implications for understanding regional development, world cities, production location, and the manner in which production systems âtouch downâ in different
places
Laser vision : lidar as a transformative tool to advance critical zone science
© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hydrology and Earth System Sciences 19 (2015): 2881-2897, doi:10.5194/hess-19-2881-2015.Observation and quantification of the Earth's surface is undergoing a revolutionary change due to the increased spatial resolution and extent afforded by light detection and ranging (lidar) technology. As a consequence, lidar-derived information has led to fundamental discoveries within the individual disciplines of geomorphology, hydrology, and ecology. These disciplines form the cornerstones of critical zone (CZ) science, where researchers study how interactions among the geosphere, hydrosphere, and biosphere shape and maintain the "zone of life", which extends from the top of unweathered bedrock to the top of the vegetation canopy. Fundamental to CZ science is the development of transdisciplinary theories and tools that transcend disciplines and inform other's work, capture new levels of complexity, and create new intellectual outcomes and spaces. Researchers are just beginning to use lidar data sets to answer synergistic, transdisciplinary questions in CZ science, such as how CZ processes co-evolve over long timescales and interact over shorter timescales to create thresholds, shifts in states and fluxes of water, energy, and carbon. The objective of this review is to elucidate the transformative potential of lidar for CZ science to simultaneously allow for quantification of topographic, vegetative, and hydrological processes. A review of 147 peer-reviewed lidar studies highlights a lack of lidar applications for CZ studies as 38 % of the studies were focused in geomorphology, 18 % in hydrology, 32 % in ecology, and the remaining 12 % had an interdisciplinary focus. A handful of exemplar transdisciplinary studies demonstrate lidar data sets that are well-integrated with other observations can lead to fundamental advances in CZ science, such as identification of feedbacks between hydrological and ecological processes over hillslope scales and the synergistic co-evolution of landscape-scale CZ structure due to interactions amongst carbon, energy, and water cycles. We propose that using lidar to its full potential will require numerous advances, including new and more powerful open-source processing tools, exploiting new lidar acquisition technologies, and improved integration with physically based models and complementary in situ and remote-sensing observations. We provide a 5-year vision that advocates for the expanded use of lidar data sets and highlights subsequent potential to advance the state of CZ science.The workshop forming the impetus for this
paper was funded by the National Science Foundation (EAR
1406031). Additional funding for the workshop and planning
was provided to S. W. Lyon by the Swedish Foundation for
International Cooperation in Research and Higher Education
(STINT grant no. 2013-5261). A. A. Harpold was supported by an
NSF fellowship (EAR 1144894)
Algae Drive Enhanced Darkening of Bare Ice on the Greenland Ice Sheet
Surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the ice sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the ice sheet. The impact of algae on bare ice darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare ice darkening, and incorporating the algal darkening effect will improve mass balance and sea level projections of the Greenland ice sheet and ice masses elsewhere
The decline and rise of neighbourhoods: the importance of neighbourhood governance
There is a substantial literature on the explanation of neighbourhood change. Most of this literature concentrates on identifying factors and developments behind processes of decline. This paper reviews the literature, focusing on the identification of patterns of neighbourhood change, and argues that the concept of neighbourhood governance is a missing link in attempts to explain these patterns. Including neighbourhood governance in the explanations of neighbourhood change and decline will produce better explanatory models and, finally, a better view about what is actually steering neighbourhood change
Green Criminology Before âGreen Criminologyâ: Amnesia and Absences
Although the first published use of the term âgreen criminologyâ seems to have been made by Lynch (Green criminology. Aldershot, Hampshire, 1990/2006), elements of the analysis and critique represented by the term were established well before this date. There is much criminological engagement with, and analysis of, environmental crime and harm that occurred prior to 1990 that deserves acknowledgement. In this article, we try to illuminate some of the antecedents of green criminology. Proceeding in this way allows us to learn from âabsencesâ, i.e. knowledge that existed but has been forgotten. We conclude by referring to green criminology not as an exclusionary label or barrier but as a symbol that guides and inspires the direction of research
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The Shaping of Form: Exploring Designersâ Use of Aesthetic Knowledge
Research on design and designers has emphasized the tacit nature of the aesthetic knowledge that these professionals draw upon to make decisions about formal properties of objects and spaces, but is less clear about how design teams address the difficulties associated with expressing and sharing this type of knowledge. A ten-month ethnography in a design consultancy revealed a range of multimodal and cross-modal ways in which members of a design team compensate their imperfect capacity of articulating verbally their aesthetic knowledge in order to gradually construct a common knowledge base enabling creative collaboration. In so doing, our study offers two main contributions. It illuminates the interplay between designersâ aesthetic experiences, visceral responses, and intuitive cognitive processes that enable designers to draw upon their aesthetic knowledge to support the collective accomplishment of their task, and provides an interpretation of the design process as a form of âcreativeâ intuition driven by emotional reactions to environmental stimuli and emerging formal solutions
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