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Articles 1 - 9 of 9
Full-Text Articles in Geography
Enso And Iod Teleconnections For African Ecosystems: Evidence Of Destructive Interference Between Climate Oscillations, Christopher A. Williams, N. P. Hanan
Enso And Iod Teleconnections For African Ecosystems: Evidence Of Destructive Interference Between Climate Oscillations, Christopher A. Williams, N. P. Hanan
Geography
Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's photosyntheis have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO …
Market Intermediaries And Rural People In Bolivia's Forest Products Sector: Are Trusting Partnerships Possible?, James T. Murphy, Mary Lawhon
Market Intermediaries And Rural People In Bolivia's Forest Products Sector: Are Trusting Partnerships Possible?, James T. Murphy, Mary Lawhon
Geography
Decentralization in access to and control of Bolivia's forest resources, coupled with a rising global demand for tropical hardwoods, raises important questions about whether increased trade and community forest management (CFM) initiatives can enable forms of market integration that have more favourable outcomes for rural communities. This paper assesses the prospects for such a transition through an examination of the relationships linking wood product market intermediaries (brokers and buyers) to rural suppliers and forest communities in Bolivia. The analysis centres on whether trust - conceptualized as a power-laden sociospatial process driven by multiscalar factors - can evolve between buyers and …
Death To Kappa: Birth Of Quantity Disagreement And Allocation Disagreement For Accuracy Assessment, Robert Gilmore Pontius, Marco Millones
Death To Kappa: Birth Of Quantity Disagreement And Allocation Disagreement For Accuracy Assessment, Robert Gilmore Pontius, Marco Millones
Geography
The family of Kappa indices of agreement claim to compare a map's observed classification accuracy relative to the expected accuracy of baseline maps that can have two types of randomness: (1) random distribution of the quantity of each category and (2) random spatial allocation of the categories. Use of the Kappa indices has become part of the culture in remote sensing and other fields. This article exam- ines five different Kappa indices, some of which were derived by the first author in 2000. We expose the indices' properties mathematically and illustrate their limitations graphically, with emphasis on Kappa's use of …
Utilizing Temporally Invariant Calibration Sites To Classify Multiple Dates And Types Of Satellite Imagery, Joe Fortier, John Rogan, Curtis E. Woodcock, Daniel Miller Runfola
Utilizing Temporally Invariant Calibration Sites To Classify Multiple Dates And Types Of Satellite Imagery, Joe Fortier, John Rogan, Curtis E. Woodcock, Daniel Miller Runfola
Geography
Mapping past time periods (retrospective mapping) using remotely sensed data is hindered by a lack of coincident calibration and validation information. The identification of features of same ground cover invariant across time and their use as calibration and validation data addresses this challenge by: (a) streamlining the process of image calibration for multiple dates, and (b) allowing each image to generate its own spectral signature. This study investigates the use of temporally invariant calibration and validation data to map land-cover in Massachusetts, employing five satellite images collected from five separate dates and different sensors. The results indicate that this technique …
Does Terrestrial Drought Explain Global Co 2 Flux Anomalies Induced By El Niño?, C. R. Schwalm, Christopher A. Williams, K. Schaefer, I. Baker, G. J. Collatz, C. Rödenbeck
Does Terrestrial Drought Explain Global Co 2 Flux Anomalies Induced By El Niño?, C. R. Schwalm, Christopher A. Williams, K. Schaefer, I. Baker, G. J. Collatz, C. Rödenbeck
Geography
The El Niño Southern Oscillation is the dominant year-to-year mode of global climate variability. El Niño effects on terrestrial carbon cycling are mediated by associated climate anomalies, primarily drought, influencing fire emissions and biotic net ecosystem exchange (NEE). Here we evaluate whether El Niño produces a consistent response from the global carbon cycle. We apply a novel bottom-up approach to estimating global NEE anomalies based on FLUXNET data using land cover maps and weather reanalysis. We analyze 13 years (1997-2009) of globally gridded observational NEE anomalies derived from eddy covariance flux data, remotely-sensed fire emissions at the monthly time step, …
Spatial And Interannual Variability Of Dissolved Organic Matter In The Kolyma River, East Siberia, Observed Using Satellite Imagery, Claire G. Griffin, Karen E. Frey, John Rogan, Robert M. Holmes
Spatial And Interannual Variability Of Dissolved Organic Matter In The Kolyma River, East Siberia, Observed Using Satellite Imagery, Claire G. Griffin, Karen E. Frey, John Rogan, Robert M. Holmes
Geography
The Kolyma River basin in northeastern Siberia, the sixth largest river basin draining to the Arctic Ocean, contains vast reserves of carbon in Pleistocene-aged permafrost soils. Permafrost degradation, as a result of climate change, may cause shifts in riverine biogeochemistry as this old source of organic matter is exposed. Satellite remote sensing offers an opportunity to complement and extrapolate field sampling of dissolved organic matter in this expansive and remote region. We develop empirically based algorithms that estimate chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in the Kolyma River and its major tributaries in the vicinity of …
Evaluation Of Species Distribution Model Algorithms For Fine-Scale Container-Breeding Mosquito Risk Prediction, C. Khatchikian, Florencia Sangermano, D. Kendell, T. Livdahl
Evaluation Of Species Distribution Model Algorithms For Fine-Scale Container-Breeding Mosquito Risk Prediction, C. Khatchikian, Florencia Sangermano, D. Kendell, T. Livdahl
Geography
The present work evaluates the use of species distribution model (SDM) algorithms to classify high densities of small container-breeding Aedes mosquitoes (Diptera: Culicidae) on a fine scale in the Bermuda Islands. Weekly ovitrap data collected by the Department of Health, Bermuda for the years 2006 and 2007 were used for the models. The models evaluated included the algorithms Bioclim, Domain, GARP (genetic algorithm for rule-set prediction), logistic regression and MaxEnt (maximum entropy). Models were evaluated according to performance and robustness. The area under the receiver operating characteristic curve was used to evaluate each model's performance, and robustness was assessed according …
Theorizing Practice In Economic Geography: Foundations, Challenges, And Possibilities, Andrew Jones, James T. Murphy
Theorizing Practice In Economic Geography: Foundations, Challenges, And Possibilities, Andrew Jones, James T. Murphy
Geography
Over the last decade or so there has been an identifiable shift in the interests of many economic geographers towards a concern with practices: stabilized, routinized, or improvised social actions that constitute and reproduce economic space, and through and within which socioeconomic actors and communities embed knowledge, organize production activities, and interpret and derive meaning from the world. Although this shift has gained significant momentum its general theoretical significance remains somewhat unclear and the concept is vulnerable to criticisms that it is incoherent, too 'micro-scale' in emphasis, unable to provide valid links between everyday practices and higher-order phenomena (eg, institutions, …
Detection Of The Timing And Duration Of Snowmelt In The Hindu Kush-Himalaya Using Quikscat, 2000-2008, Prajjwal K. Panday, Karen E. Frey, Bardan Ghimire
Detection Of The Timing And Duration Of Snowmelt In The Hindu Kush-Himalaya Using Quikscat, 2000-2008, Prajjwal K. Panday, Karen E. Frey, Bardan Ghimire
Geography
The Hindu Kush-Himalayan (HKH) region holds the largest mass of ice in Central Asia and is highly vulnerable to global climate change, experiencing significant warming (0.21 ± 0.08 °C/decade) over the past few decades. Accurate monitoring of the timing and duration of snowmelt across the HKH region is important, as this region is expected to experience further warming in response to increased greenhouse gas forcing. Despite the many advantages and applications of satellite-derived radar scatterometer data shown for capturing ice and snow melt dynamics at high latitudes, similar comprehensive freeze/thaw detection studies at lower latitudes (including the HKH region) are …