724 research outputs found
Mitigating the effects of hydrologic variability in Ethiopia: an assessment of investments in agricultural and transportation infrastructure, energy and hydroclimatic forecasting
Ethiopia is at a critical crossroads with a burgeoning population, a severely depressed national economy, insufficient agricultural production, and a minimal number of devel- oped energy sources. This study assesses how investment in and management of water resources, together with related policy reforms, may mitigate the negative effects of hydrologic variability on the performance and structure of the Ethiopian economy. This is accomplished by identifying interventions both aimed at managing hydrologic variabil- ity, and at decreasing the vulnerability of the economy to potential shocks. The areas
of focus include increased infrastructure for agricultural irrigation and roads, large-scale hydropower generation, and a precipitation forecast model.
A dynamic climate agro-economic model of Ethiopia is utilized to assess irrigation and road construction investment strategies in comparison to a baseline scenario over a 12-year time horizon. Although both investments create positive economic boosts, the irrigation investment, on average, slightly outperforms the road investment, producing an average gdP growth rate of 0.95% versus 0.75% over the baseline scenario, along with lower associated poverty and malnutrition rates. The benefit-cost (b-c) ratios for the projects also favor the irrigation investment.
The upper Blue nile basin harbors considerable untapped potential for irrigation and large-scale hydropower development and expansion. An integrated model is employed to assess potential conditions based on hydrologic variability and streamflow policies. The model indicates that large-scale development typically produces b-c ratios from 1.6- 2.1 under historical climate regimes for the projects specified. Climate change scenar- ios indicate potential for small b-c increases, but reflect possible significant decreases. stochastic modeling of scenarios representing a doubling of the historical frequency of El ninÌo events indicates b-c ratios as low as 1.0 due to a lack of timely water. An evaluation of expected energy growth rates reinforces the need for significant economic planning and the necessity of securing energy trade contracts prior to extensive devel- opment. A Ramsey growth model for energy development specifies project multipliers on total gdP over the 100-year simulation ranging from 1.7-5.2, for various climatologic conditions.
The Blue nile basin also holds possibility for improvement in rain-fed agricultural pro- duction through precipitation forecasting. one-season lead predictors for forecasting of the Kiremt season precipitation are identified from the large scale ocean-atmosphere- land system. This forecast is of tremendous value, giving farmers crucial indication
of potential future climatic conditions, and is a solid improvement over climatology, as currently utilized by the Ethiopian national Meteorological Institute. Using crop yield potential from the 1961-2000 period and general seed costs, farmers basing cropping decisions on the forecast model, in lieu of climatology, would have experienced superior net incomes
Impacts of considering climate variability on investment decisions in Ethiopia:
"Extreme interannual variability of precipitation within Ethiopia is not uncommon, inducing droughts or floods and often creating serious repercussions on agricultural and non-agricultural commodities. An agro-economic model, including mean climate variables, was developed to assess irrigation and road construction investment strategies in comparison to a baseline scenario over a 12-year time horizon. The motivation for this work is to evaluate whether the inclusion of climate variability in the model has a significant effect on prospective investment strategies and the resulting country-wide economy. The mean climate model is transformed into a variable climate model by dynamically adding yearly climate-yield factors, which influence agricultural production levels and linkages to non-agricultural goods. Nine sets of variable climate data are processed by the new model to produce an ensemble of potential economic prediction indicators. Analysis of gross domestic product and poverty rate reveal a significant overestimation of the country's future welfare by the mean climate model method, in comparison to probability density functions created from the variable climate ensemble. The ensemble is further utilized to demonstrate risk assessment capabilities. The addition of climate variability to the agro-economic model provides a framework, including realistic ranges of economic values, from which Ethiopian planners may make strategic decisions." Authors' abstractClimate variability, Water, Droughts, Flooding, Irrigation Economic aspects, Road construction Economic aspects, Investments, Economic situation, Agro-economic model,
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Review of Downscaling Methodologies for Africa Climate Applications
Downscaling is the term used to describe the various methods used to translate the climate projections from coarse resolution GCMs to finer resolutions deemed more useful for assessing impacts. Projections of future climate are produced using complex, coupled atmosphere-ocean models (GCMs). The GCMs are most reliable at the continental scale. Due to the inherent uncertainty of the climate system and the inevitable existence of model errors, multi-model ensembling is the recommended approach for characterizing expected climate changes. As downscaling is dependent on the ability of GCMs to successfully project the climate change signal, it is limited to where that signal is clear. Assessments of climate change in Africa indicate some consensus of reduced winter rainfall in southern Africa, increased annual rainfall in east Africa and uncertainty for the rest of Africa. Selection of GCMs that "do better" over Africa, or any region, is difficult and probably not warranted, given the general parity in model skill and the difficulty in identifying which models are more skillful. Ensemble means or medians offer the highest level of projection accuracy. Downscaling approaches are generally categorized as dynamical, using regional climate models, and statistical, using empirical relationships. However, dynamical downscaling often includes statistical modeling in the form of "bias correction." Dynamical downscaling is useful for incorporating topographic features, such as strong orography, and land use and vegetation. It is recommended where those features play a significant role in regional climate. However, computational time and the uncertainties that accompany complex models outweigh the benefits of dynamical downscaling where these features are not significant. The spatial resolution that can be achieved is on the order of tens of kilometers. Statistical downscaling is simpler and more efficient than dynamical downscaling. It is preferred where estimates of specific variables, especially at point locations, are sought for input to sector models (e.g., hydrologic models) or decision making. However, statistical modeling can mask a true understanding of regional climate dynamics and estimates may be overconfident. In summary, downscaling is best understood as an attempt to increase the understanding of climate change influences at the regional scale. In that context, a variety of methodologies should be explored, using all tools possible to increase that understanding. A set of "Best Practices" is recommended for pursuing this effort
UV-Optical Pixel Maps of Face-On Spiral Galaxies -- Clues for Dynamics and Star Formation Histories
UV and optical images of the face-on spiral galaxies NGC 6753 and NGC 6782
reveal regions of strong on-going star formation that are associated with
structures traced by the old stellar populations. We make NUV--(NUV-I) pixel
color-magnitude diagrams (pCMDs) that reveal plumes of pixels with strongly
varying NUV surface brightness and nearly constant I surface brightness. The
plumes correspond to sharply bounded radial ranges, with (NUV-I) at a given NUV
surface brightness being bluer at larger radii. The plumes are parallel to the
reddening vector and simple model mixtures of young and old populations, thus
neither reddening nor the fraction of the young population can produce the
observed separation between the plumes. The images, radial surface-brightness,
and color plots indicate that the separate plumes are caused by sharp declines
in the surface densities of the old populations at radii corresponding to disk
resonances. The maximum surface brightness of the NUV light remains nearly
constant with radius, while the maximum I surface brightness declines sharply
with radius. An MUV image of NGC 6782 shows emission from the nuclear ring. The
distribution of points in an (MUV-NUV) vs. (NUV-I) pixel color-color diagram is
broadly consistent with the simple mixture model, but shows a residual trend
that the bluest pixels in (MUV-NUV) are the reddest pixels in (NUV-I). This may
be due to a combination of red continuum from late-type supergiants and [SIII]
emission lines associated with HII regions in active star-forming regions. We
have shown that pixel mapping is a powerful tool for studying the distribution
and strength of on-going star formation in galaxies. Deep, multi-color imaging
can extend this to studies of extinction, and the ages and metallicities of
composite stellar populations in nearby galaxies.Comment: LaTeX with AASTeX style file, 29 pages with 12 figures (some color,
some multi-part). Accepted for publication in The Astrophysical Journa
Observing System Simulation Experiment (OSSE) for the HyspIRI Spectrometer Mission
The OSSE software provides an integrated end-to-end environment to simulate an Earth observing system by iteratively running a distributed modeling workflow based on the HyspIRI Mission, including atmospheric radiative transfer, surface albedo effects, detection, and retrieval for agile exploration of the mission design space. The software enables an Observing System Simulation Experiment (OSSE) and can be used for design trade space exploration of science return for proposed instruments by modeling the whole ground truth, sensing, and retrieval chain and to assess retrieval accuracy for a particular instrument and algorithm design. The OSSE in fra struc ture is extensible to future National Research Council (NRC) Decadal Survey concept missions where integrated modeling can improve the fidelity of coupled science and engineering analyses for systematic analysis and science return studies. This software has a distributed architecture that gives it a distinct advantage over other similar efforts. The workflow modeling components are typically legacy computer programs implemented in a variety of programming languages, including MATLAB, Excel, and FORTRAN. Integration of these diverse components is difficult and time-consuming. In order to hide this complexity, each modeling component is wrapped as a Web Service, and each component is able to pass analysis parameterizations, such as reflectance or radiance spectra, on to the next component downstream in the service workflow chain. In this way, the interface to each modeling component becomes uniform and the entire end-to-end workflow can be run using any existing or custom workflow processing engine. The architecture lets users extend workflows as new modeling components become available, chain together the components using any existing or custom workflow processing engine, and distribute them across any Internet-accessible Web Service endpoints. The workflow components can be hosted on any Internet-accessible machine. This has the advantages that the computations can be distributed to make best use of the available computing resources, and each workflow component can be hosted and maintained by their respective domain experts
Connectivity between white shark populations off Central California, USA and Guadalupe Island, Mexico
Marine animals often move beyond national borders and exclusive economic zones resulting in a need for trans-boundary management spanning multiple national jurisdictions. Highly migratory fish vulnerable to over-exploitation require protections at international level, as exploitation practices can be disparate between adjacent countries and marine jurisdictions. In this study we collaboratively conducted an analysis of white shark connectivity between two main aggregation regions with independent population assessment and legal protection programs; one off central California, USA and one off Guadalupe Island, Mexico. We acoustically tagged 326 sub-adult and adult white sharks in central California (n=210) and in Guadalupe Island (n=116) with acoustic transmitters between 2008-2019. Of the 326 tagged white sharks, 30 (9.20%) individuals were detected at both regions during the study period. We used a Bayesian implementation of logistic regression with a binomial distribution to estimate the effect of sex, maturity, and tag location to the response variable of probability of moving from one region to the other. While nearly one in ten individuals in our sample were detected in both regions over the study period, the annual rate of trans-regional movement was low (probability of movement = 0.015 yr-1, 95% credible interval = 0.002, 0.061). Sub-adults were more likely than adults to move between regions and sharks were more likely to move from Guadalupe Island to central California, however, sex, and year were not important factors influencing movement. This first estimation of demographic-specific trans-regional movement connecting US and Mexico aggregations with high seasonal site fidelity represents an important step to future international management and assessment of the northeastern Pacific white shark population as a whole
The Frequency of Barred Spiral Galaxies in the Near-IR
We have determined the fraction of barred galaxies in the H-band for a
statistically well-defined sample of 186 spirals drawn from the Ohio State
University Bright Spiral Galaxy survey. We find 56% of our sample to be
strongly barred at H, while another 16% is weakly barred. Only 27% of our
sample is unbarred in the near-infrared. The RC3 and the Carnegie Atlas of
Galaxies both classify only about 30% of our sample as strongly barred. Thus
strong bars are nearly twice as prevalent in the near-infrared as in the
optical. The frequency of genuine optically hidden bars is significant, but
lower than many claims in the literature: 40% of the galaxies in our sample
that are classified as unbarred in the RC3 show evidence for a bar in the
H-band, while for the Carnegie Atlas this fraction is 66%. Our data reveal no
significant trend in bar fraction as a function of morphology in either the
optical or H-band. Optical surveys of high redshift galaxies may be strongly
biased against finding bars, as bars are increasingly difficult to detect at
bluer rest wavelengths.Comment: LaTeX with AASTeX style file, 23 pages with 6 figures. Accepted for
publication in The Astronomical Journal (Feb. 2000
Non-reductivism and the Metaphilosophy of Mind
This paper discusses the metaphilosophical assumptions that have dominated analytic philosophy of mind, and how they gave rise to the central question that the best-known forms of non-reductivism available have sought to answer, namely: how can mind fit within nature? Its goal is to make room for forms of non-reductivism that have challenged the fruitfulness of this question, and which have taken a different approach to the so-called âplacementâ problem. Rather than trying to solve the placement problem, the forms of non-reductivism discussed in this paper have put pressure on the metaphilosophical assumptions that have given rise to the question of the place of mind in nature in the first instance
Standard Model Contributions to the Neutrino Index of Refraction in the Early Universe
With the standard electroweak interactions, the lowest-order coherent forward
scattering amplitudes of neutrinos in a CP symmetric medium (such as the early
universe) are zero, and the index of refraction of a propagating neutrino can
only arise from the expansion of gauge boson propagators, from radiative
corrections, and from new physics interactions. Motivated by nucleosynthesis
constraints on a possible sterile neutrino (suggested by the solar neutrino
deficit and a possible neutrino), we calculate the standard model
contributions to the neutrino index of refraction in the early universe,
focusing on the period when the temperature was of the order of a few . We
find sizable radiative corrections to the tree level result obtained by the
expansion of the gauge boson propagator. For the leading log correction is about , while for
the correction is about
. Depending on the family mixing (if any), effects from different family
scattering can be dominated by radiative corrections. The result for
is zero at one-loop level, even if neutrinos are
massive. The cancellation of infrared divergence in a coherent process is also
discussed.Comment: 46pp, 13 figures (not included), UPR-0495
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