Bogotá, Colombia
Bogotá, Colombia

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This paper presents a finite difference, time-layer-weighted, bidirectional algorithm that solves the Fokker-Planck-Kolmogorov (FPK) equation in order to forecast the probability density curve (PDC) of the monthly affluences to the Betania hydropower reservoir in the upper part of the Magdalena River in Colombia. First, we introduce a deterministic kernel to describe the basic dynamics of the rainfall-runoff process and show its optimisation using the S/σ△ performance criterion as a goal function. Second, we introduce noisy parameters into this model, configuring a stochastic differential equation that leads to the corresponding FPK equation. We discuss the set-up of suitable initial and boundary conditions for the FPK equation and the introduction of an appropriate Courant-Friederich-Levi condition for the proposed numerical scheme that uses time-dependent drift and diffusion coefficients. A method is proposed to identify noise intensities. The suitability of the proposed numerical scheme is tested against an analytical solution and the general performance of the stochastic model is analysed using a combination of the Kolmogorov, Pearson and Smirnov statistical criteria. © IWA Publishing 2010.


Lafon T.,Aereo | Fowler J.,University of Montana | Jimenez J.F.,Institute Hidrologia | Cordoba G.J.T.,Institute Hidrologia
Bulletin of the American Meteorological Society | Year: 2014

Radiosonde-collected data are of vital importance to a wide variety of studies that aim at understanding the interaction between land surface and the atmosphere, among others. However, atmospheric measurements in developing countries, some of which encompass areas critical to the regulation of global climate, are sparse due to the lack of funding allocated toward collecting such data, and therefore fail to meet the standards set by the World Meteorological Organization (WMO). WMO's reference network for upper-air climate observations (GRUAN) program is working toward providing long-term, high-quality, accurate climate data. A glider model developed by GPSBoomerang, the 'DataBird', has shown promising results with regard to the possibility for its use by national weather stations. Two major issues currently hamper future development and commercialization of this technology. The first is how to have reusable radiosondes while keeping the market viable for the sonde manufacturers, and the need for consistent and effective governmental aviation regulations for developing and flying glidersondes.


Grant
Agency: European Commission | Branch: FP7 | Program: CP | Phase: SPA.2010.1.1-04 | Award Amount: 3.60M | Year: 2010

ReCover project will develop beyond state-of-the-art service capabilities to support fighting deforestation and forest degradation in the tropical region. The pilot service capabilities mean provision of a monitoring system of forest cover and forest cover changes and biomass including a robust accuracy assessment. The capabilities are based on utilizing mainly space-borne earth observation data and in-situ data. The service development is controlled by specific user requirements that are expressed through Service Level Agreements (SLA) between the ReCover consortium and six users. The services prepare particularly for the implementation of the post-Kyoto climate treaty and the REDD\. Service roll-out and expansion to the community outside the project and present pilot users is a key activity of ReCover. The outside community includes but is not restricted to TREES-3 project, GSE Forest Monitoring Extension, FRA, and GEO. The scientific viewpoint that reaches beyond the state-of-the-art techniques is the leading baseline of the study. The main research focus in ReCover is to develop a sound statistical concept and validation procedure in the production, apply very high resolution image data to improve result reliability, estimate biomass and degradation as well as their change, define the role of radar data in REDD related services, and build standardized service system with a capacity building concept. The consortium consists of nine leading research and industrial partners of which one is an SME. Three partners are from REDD eligible countries. The high impact value of ReCover is achieved by working directly for and with the customers and with local research partners, creating novel, trustworthy and standardized but affordable services and applying them in INSPIRE compatible service environment. The long-term service sustainability is concerned including evaluation of the potential of new missions such as the Sentinels.


Nunez J.,Centro Del Agua Para Zonas Aridas Y Semiaridas Of America Latina Y El Caribe | Nunez J.,University of La Serena | Hallack-Alegria M.,Autonomous University of Baja California | Cadena M.,Institute Hidrologia
Journal of Hydrology | Year: 2016

Hydrologic frequency analysis is a statistical technique for the assessment of natural hazards, particularly the so-called water hazards caused exclusively by extreme hydrologic events. In particular, L-moments based regional frequency analysis (RFA-LM) has being adopted as the standard method for hydrologic frequency analysis in many parts of the world and for many other applications relating to hydrological extremes. However, despite the widespread use of RFA-LM, its application at large network and high and complex spatial scale conditions (LNHCSSC) has been poorly studied. The lack of studies about RFA-LM under such conditions and its use preferentially at subnational scales and areas with low number of rain gauge stations, or based on grid data, may be explained by the fact that the most difficult, less robust, and most subjective stage of RFA-LM is the delineation of homogeneous regions. This work proposes an integral procedure for the application of RFA-LM under LNHCSSC. The proposed method is applied to the study of drought event frequency in three case studies from Latin America, and incorporates innovating aspects compared to the state-of-the-art RFA-LM. These aspects are specifically (a) the decoupling of the cause of homogeneity from the regionalization stage; (b) the proposal of regionalization efficiency metrics; (c) the development of a regionalization algorithm; and (d) the development of a frequency estimation and mapping method for ungauged sites. © 2016 Elsevier B.V.


Pena M.A.,National University of Colombia | Pena M.A.,Institute Hidrologia | Duque A.,National University of Colombia
Forest Ecology and Management | Year: 2013

In this study, we aimed to identify the main factors that affect the dynamics and rates of aboveground biomass (AGB) accumulation in secondary forests located in the interandean valleys of Colombia. We used two censuses performed on trees with a diameter at breast height of. ≥10. cm in 10 1-ha plots to answer the following questions: (1) Does prior use of the land for raising crops (instead of pastureland for cattle ranching) promote an increase in the rate of AGB accumulation? (2) To what extent did climate, soil characteristics, the functional traits of resident species, and/or stand age affect the stocks and dynamics of the AGB in these secondary forests? We did not find any evidence that prior land use for cattle ranching had a negative effect on the tree AGB-accumulation rate, when compared with land previously used for raising crops. Greater AGB stocks at an intermediate fertility point may be associated with a higher abundance of tall, short-lived, fast-growth pioneer species. Tree mortality rates in secondary forests were primarily determined by the forest's composition and the variation in the amount of rainfall between sites. Soil fertility, which is known to accelerate the growth rate of plant species, was significantly and positively associated with the rate of AGB recruitment. We did not find any evidence for a negative correlation between wood density and growth, as has been reported for primary tropical forests. The net AGB change (%) was primarily associated with the low soil-fertility characteristics of sandy well-drained soils that could, in the presence of steep slopes, increase forest dynamics. Land restoration that restores the natural cycle of secondary forests could assist in the mitigation of global warming by promoting key environmental functions, such as carbon sequestration. © 2013 Elsevier B.V.


Duque A.,National University of Colombia | Feeley K.J.,Florida International University | Feeley K.J.,Fairchild Tropical Botanic Garden | Cabrera E.,Institute Hidrologia | And 2 more authors.
Tropical Conservation Science | Year: 2014

Carbon-centric conservation strategies such as the United Nation's program to Reduce CO2 Emissions from Deforestation and Degradation (REDD+), are expected to simultaneously reduce net global CO2 emissions and mitigate species extinctions in regions with high endemism and diversity, such as the Tropical Andes Biodiversity Hotspot. Using data from the northern Andes, we show, however, that carbon-focused conservation strategies may potentially lead to increased risks of species extinctions if there is displacement (i.e., "leakage") of land-use changes from forests with large aboveground biomass stocks but relatively poor species richness and low levels of endemism, to forests with lower biomass stocks but higher species richness and endemism, as are found in the Andean highlands (especially low-biomass non-tree growth forms such as herbs and epiphytes that are often overlooked in biological inventories). We conclude that despite the considerable potential benefits of REDD+ and other carbon-centric conservation strategies, there is still a need to develop mechanisms to safeguard against possible negative effects on biodiversity in situations where carbon stocks do not covary positively with species diversity and endemism. © Alvaro Duque, Kenneth J. Feeley, Edersson Cabrera, Ricardo Callejas and Alvaro Idarraga.


Asner G.P.,Carnegie Institution for Science | Clark J.K.,Carnegie Institution for Science | Mascaro J.,Carnegie Institution for Science | Galindo Garcia G.A.,Institute Hidrologia | And 15 more authors.
Biogeosciences | Year: 2012

High-resolution mapping of tropical forest carbon stocks can assist forest management and improve implementation of large-scale carbon retention and enhancement programs. Previous high-resolution approaches have relied on field plot and/or light detection and ranging (LiDAR) samples of aboveground carbon density, which are typically upscaled to larger geographic areas using stratification maps. Such efforts often rely on detailed vegetation maps to stratify the region for sampling, but existing tropical forest maps are often too coarse and field plots too sparse for high-resolution carbon assessments. We developed a top-down approach for high-resolution carbon mapping in a 16.5 million ha region (> 40%) of the Colombian Amazon - a remote landscape seldom documented. We report on three advances for large-scale carbon mapping: (i) employing a universal approach to airborne LiDAR-calibration with limited field data; (ii) quantifying environmental controls over carbon densities; and (iii) developing stratification- and regression-based approaches for scaling up to regions outside of LiDAR coverage. We found that carbon stocks are predicted by a combination of satellite-derived elevation, fractional canopy cover and terrain ruggedness, allowing upscaling of the LiDAR samples to the full 16.5 million ha region. LiDAR-derived carbon maps have 14% uncertainty at 1 ha resolution, and the regional map based on stratification has 28% uncertainty in any given hectare. High-resolution approaches with quantifiable pixel-scale uncertainties will provide the most confidence for monitoring changes in tropical forest carbon stocks. Improved confidence will allow resource managers and decision makers to more rapidly and effectively implement actions that better conserve and utilize forests in tropical regions. © 2012 Author(s). CC Attribution 3.0 License.


Ortiz-Royero J.C.,Universidad del Norte, Colombia | Otero L.J.,Universidad del Norte, Colombia | Restrepo J.C.,Universidad del Norte, Colombia | Ruiz J.,Universidad del Norte, Colombia | Cadena M.,Institute Hidrologia
Natural Hazards and Earth System Sciences | Year: 2013

Extreme ocean waves in the Caribbean Sea are commonly related to the effects of storms and hurricanes during the months of June through November. The collapse of 200 m of the Puerto Colombia pier in March 2009 revealed the effects of meteorological phenomena other than storms and hurricanes that may be influencing the extreme wave regime in the Colombian Caribbean. The marked seasonality of these atmospheric fronts was established by analyzing the meteorological-marine reports of the Instituto de Hidrología, Meteorología y Estudios Ambientales of Colombia (IDEAM, based on its initials in Spanish) and the Centro de Investigación en Oceanografía y Meteorología of Colombia (CIOH, based on its initials in Spanish) during the last 16 yr. The highest number of cold fronts was observed during the months of January, February, and March, with 6 fronts occurring per year. An annual trend was observed and the highest number of fronts occurred in 2010 (20 in total); moreover, an annual strong relationship between the maximum average wave values and the cold fronts in the central zone of the Colombian Caribbean during the first three months of the year was established. In addition, the maximum values of the significant height produced by the passage of cold fronts during the last 16 yr were identified. Although the Colombian Caribbean has been affected by storms and hurricanes in the past, this research allows us to conclude that there is a strong relationship between cold fronts and the largest waves in the Colombian Caribbean during the last 16 yr, which have caused damage to coastal infrastructure. We verified that the passage of a cold front corresponded to the most significant extreme wave event of the last two decades in the Colombian Caribbean, which caused the structural collapse of the Puerto Colombia pier, located near the city of Barranquilla, between 5 and 10 March 2009. This information is invaluable when evaluating average and extreme wave regimes for the purpose of informing the design of structures in this region of the Caribbean. © Author(s) 2013.


Armenteras D.,National University of Colombia | Cabrera E.,Institute Hidrologia | Rodriguez N.,National University of Colombia | Rodriguez N.,Autonomous University of Barcelona | Retana J.,Autonomous University of Barcelona
Regional Environmental Change | Year: 2013

Global tropical deforestation continues to occur at high rates despite political attention. National-level forest baselines are being established all over the world to guide the implementation of several policy mechanisms. However, identifying the direct and indirect drivers of deforestation and understanding the complexity of their interlinkages are often difficult. We first analyzed deforestation between 1990 and 2005 at the national level and found an annual deforestation rate of 0.62 %. Next, we performed separate analyses for four natural regions in Colombia and found annual deforestation rates between 0.42 and 1.92 %. Using general linear models, we identified several direct causes and underlying factors influencing deforestation at the national level: rural population density, cattle, protected areas, and slope. Significant differences in deforestation rates and causes were found across regions. In the Caribbean region, drivers of loss are urban population, unsatisfied basic needs, slope, and precipitation and four land use variables (illicit crops, pastures, cattle, and fires). In the Orinoco region, crops are the main driver of forest loss, and in the Amazonian region, deforestation is primarily due to fires related to the colonization front. Policy mechanisms will have to take into account regional patterns to successfully balance development and forest preservation in Colombia. © 2013 Springer-Verlag Berlin Heidelberg.


Huggel C.,University of Zürich | Rohrer M.,Meteodat GmbH | Calanca P.,ART Agroscope Reckenholz Tänikon | Salzmann N.,University of Zürich | And 3 more authors.
Eos | Year: 2012

Recent scientific assessment studies of climate change impacts, including those from the Intergovernmental Panel on Climate Change, provide evidence of the negative effects of climate variability and change on natural and human systems. For instance, recent climate trends have caused loss in wheat and maize production, negatively affected coral reefs, and changed characteristics of some hazards in high-mountain regions. Assessment studies furthermore suggest that related risks to ecosystems, commerce, and daily life may increase over the coming decades as temperatures warm. Adaptation to climate change is required to reduce the effects of unavoidable changes, especially for the most vulnerable regions and populations. © 2012. American Geophysical Union. All Rights Reserved.

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