A Note on Methods for Vertical Accuracy Assessment of DEMs

This study investigates the vertical accuracy of a DEMs interpolated from 1:50,000 contours with universal kriging (UK) using DEMs interpolated from 1:10,000 contours as the independent source of higher accuracy following the geospatial accuracy standards proposed by the Federal Geographic Data Committee, FGDC, (1998). In accordance with the standards, the 1:10,000 contours do not qualify as well-defined points with known horizontal position and a high degree of accuracy that are easily visible and recoverable on the ground. Hence, DEMs are created from the 1:10,000 contours and used to check the vertical accuracy of the 1:50,000 DEMs with elevation errors, an RMSE and vertical accuracy measure calculated between the 1:10,000 and 1:50,000 DEMs. Other methods of vertical accuracy assessment for the 1:50,000 DEMs include a comparison of elevation ranges, visualization of error surfaces and latitudinal and longitudinal terrain profiles.Este estudio investiga la exactitud vertical de un modelo de elevación digital interpolado desde una escala 1:50,000, usando MED interpolado de 1:10,000 con líneas de contorno como una fuente independiente de alta precisión y siguiendo los indicadores propuestos por la Federal Geographic Data Committee, FGDC, (1998). De acuerdo con esos indicadores los contornos de una escala 1: 10 000 no califican como puntos bien definidos en una posición horizontal conocida y un alto nivel de precisión, los cuales pueden ser fácilmente visibles y recolectados en el campo. Por ello, los MEDs son creados a partir de contornos a escala 10 000 y usados para corroborar la precisión vertical a una escala 1 50 000. Además, los MEDs incluyen una comparación de los rangos de elevación, visualizan errores en la superficie y los perfiles latitudinales y longitudinales.Este estudo investiga a precisão vertical de um modelo de elevação digital interpolado a partir de uma escala de 1:50.000, utilizando MED pontilhadas de 1:10000 com linhas de contorno como uma fonte independente de alta precisão e seguindo os propostos pelos indicadores do Comitê Federal de Dados Geográficos, CFDC (1998). De acordo com estes indicadores, os contornos de uma escala de 1:10.000 não são qualificadas como pontos bem definidos em uma posição horizontal conhecido e um alto nível de precisão, o que pode ser facilmente visto e recolhido no campo. Portanto, MEDs são criados a partir de escala 10.000 contornos e, utilizados para corroborar a precisão vertical numa escala 1:50000. Além disso, as MEDs incluem uma comparação de gamas de elevação, erros de superfície de exibição e perfis latitude e longitude.UCR::Sedes Regionales::Sede de Occident

A spatiotemporal natural-human database to evaluate road development impacts in an Amazon trinational frontier

Road construction and paving bring socio-economic benefits to receiving regions but can also be drivers of deforestation and land cover change. Road infrastructure often increases migration and illegal economic activities, which in turn affect local hydrology, wildlife, vegetation structure and dynamics, and biodiversity. To evaluate the full breadth of impacts from a coupled natural-human systems perspective, information is needed over a sufficient timespan to include pre- and post-road paving conditions. In addition, the spatial scale should be appropriate to link local human activities and biophysical system components, while also allowing for upscaling to the regional scale. A database was developed for the tri-national frontier in the Southwestern Amazon, where the Inter-Oceanic Highway was constructed through an area of high biological value and cultural diversity. Extensive socio-economic surveys and botanical field work are combined with remote sensing and reanalysis data to provide a rich and unique database, suitable for coupled natural-human systems research

Modeling streamflow response to persistent drought in a coastal tropical mountainous watershed, Sierra Nevada de Santa Marta, Colombia

Droughts constitute natural hazards that affect water supply for ecosystems and human livelihoods. In 2013-2016, the Caribbean experienced the worst drought since the 1950s, and climate projections for the southern Caribbean predict less rainfall by the end of the 21st century. We assessed streamflow response to drought for a watershed in the Colombian Caribbean by analyzing the effects of drought length and land cover on streamflow recovery. We generated a calibrated SWAT model and created annual and monthly drought scenarios from rainfall records. We used our model to predict water yield for selected land covers (wet forest, shade coffee, shrub, and dry forest) under drought conditions. Annual scenarios resulted in water yield reductions of ~15 mm month -1 (wet forest, coffee, and shrub) and 5 mm month -1 (dry forest) for the first month after a two-year drought. Maximum water yield reductions for monthly scenarios occurred after a 10-month drought and were ~100 mm month -1 (wet forest, coffee, and shrub) and 20 mm month -1 (dry forest). Streamflow recovered within nine months (annual scenarios), and two to eight months (monthly scenarios) after drought termination. Drought response seems to be conditioned by climatic factors (rainfall seasonality and spatial variability) and catchment properties

Reactive mercury in the troposphere: Model formation and results for Florida, the northeastern United States, and the Atlantic Ocean

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95402/1/jgrd13669.pd

Spatial complexity in fragmenting Amazonian rainforests: Do feedbacks from edge effects push forests towards an ecological threshold?

Deforestation and resulting landscape fragmentation are important concerns in many tropical areas. Deforestation is a complex process with many potential feedback loops, many of which are ignored in models that attempt to interpolate forest loss based on past deforestation rates. In addition, most ecological studies of the impacts of deforestation have focused on landscapes that are already fragmented. These studies ignore the fact that edge effects, such as anthropogenic fire, reach their maximum well before habitat connectivity is lost and may create positive feedbacks that result in further fragmentation. We developed a simple model to explore the potential influence of edge effects on fragmentation rates and used remotely sensed data from the MAP (Madre de Dios, Acre, and Pando) region of the Brazilian Amazon to parameterize the relationships of interest. Under reasonable real-world parameter combinations, edge effects can have a significant impact on deforestation rates, supporting the hypothesis that the true tipping point in a forest to pasture regime shift occurs earlier (i.e., ~50% forest loss) than analysis of a loss in connectivity would suggest (i.e., ~60% forest loss). Our results have important implications for understanding deforestation, edge-driven processes, regime shifts, and the management of complex pattern-process relationships

An Artificial Turf-Based Surrogate Surface Collector for the Direct Measurement of Atmospheric Mercury Dry Deposition

This paper describes the development of a new artificial turf surrogate surface (ATSS) sampler for use in the measurement of mercury (Hg) dry deposition. In contrast to many existing surrogate surface designs, the ATSS utilizes a three-dimensional deposition surface that may more closely mimic the physical structure of many natural surfaces than traditional flat surrogate surface designs (water, filter, greased Mylar film). The ATSS has been designed to overcome several complicating factors that can impact the integrity of samples with other direct measurement approaches by providing a passive system which can be deployed for both short and extended periods of time (days to weeks), and is not contaminated by precipitation and/or invalidated by strong winds. Performance characteristics including collocated precision, in-field procedural and laboratory blanks were evaluated. The results of these performance evaluations included a mean collocated precision of 9%, low blanks (0.8 ng), high extraction efficiency (97%–103%), and a quantitative matrix spike recovery (100%)

Regional-Scale Forest Management Maps for the Continental United States

One main challenge in environmental and ecological research is to map land use, the human intent to modify the earth's cover, using satellite data. We have mapped forest management, a land use, in the southeastern and northwestern United States, 1.5 million square kilometers, at high spatial. This is a novel study using spectral time series analysis, expert derived training data and a random forest classifier to map forest management, calculate probability and uncertainty of class membership

Modeling Streamflow Response to Persistent Drought in a Coastal Tropical Mountainous Watershed, Sierra Nevada De Santa Marta, Colombia

Droughts constitute natural hazards that affect water supply for ecosystems and human livelihoods. In 2013–2016, the Caribbean experienced the worst drought since the 1950s, and climate projections for the southern Caribbean predict less rainfall by the end of the 21st century. We assessed streamflow response to drought for a watershed in the Colombian Caribbean by analyzing the effects of drought length and land cover on streamflow recovery. We generated a calibrated SWAT model and created annual and monthly drought scenarios from rainfall records. We used our model to predict water yield for selected land covers (wet forest, shade coffee, shrub, and dry forest) under drought conditions. Annual scenarios resulted in water yield reductions of ~15 mm month−1 (wet forest, coffee, and shrub) and 5 mm month−1 (dry forest) for the first month after a two-year drought. Maximum water yield reductions for monthly scenarios occurred after a 10-month drought and were ~100 mm month−1 (wet forest, coffee, and shrub) and 20 mm month−1 (dry forest). Streamflow recovered within nine months (annual scenarios), and two to eight months (monthly scenarios) after drought termination. Drought response seems to be conditioned by climatic factors (rainfall seasonality and spatial variability) and catchment properties