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581.
Muhammad Aslam Chaudhry Robert A. Young 《Journal of the American Water Resources Association》1989,25(5):1055-1061
ABSTRACT: Linear programming models of a representative farm in a district of Pakistan's Punjab Province are formulated for the purpose of estimating the value of irrigation water. The models provide for choices among several irrigation levels for each potential crop. Solutions of the model for several water supply situations provide the basis for approximating the total, average, and marginal values of irrigation water. Prices for important crops in Pakistan are controlled at levels below their levels elsewhere in the world, so models are specified for both financial (domestic price) and economic (world price) scenarios. The value of water to society (its economic value) is high relative to the costs of some generally available water-augmenting investments, while financial values, which measure water management and allocation incentives faced by farmers, are less than the corresponding economic values. At current water supply levels, incremental returns to added water estimated from the economic model would justify investments in water-saving or water-augmenting technologies, while such a decision would be barely attractive assuming financial prices. While present government commodity price policies may serve to protect low-income and non-farm members of the population, they also inhibit farmer investments to increase the productivity of scarce irrigation water. 相似文献
582.
Venkata Srinivas Challa Jayakumar Indrcanti Julius M. Baham Chuck Patrick Monika K. Rabarison John H. Young Robert Hughes Shelton J. Swanier Mark G. Hardy Anjaneyulu Yerramilli 《Environmental Fluid Mechanics》2008,8(4):367-387
Mesoscale transport and dispersion of air pollutants from a few major point sources in the Mississippi Gulf coastal region
is calculated using a coupled modeling system consisting of the atmospheric dynamical model WRF and the lagrangian particle
model HYSPLIT. The sensitivity of the dispersion model results to the meteorological fields is studied by conducting an ensemble
of simulations using the WRF model for the same dispersion case. Several parameterization schemes for the physical processes
of boundary layer turbulence and land surface temperature/moisture prediction in WRF are used in various combinations to produce
different meteorological members which are then used for dispersion simulation. The uncertainty in the simulated concentration
probabilities to the meteorological model configurations and the ensemble mean are presented. The parameters used for determining
the uncertainties include the wind fields, temperature, area of concentration and the levels of concentration. The results
indicate that dispersion model results are influenced by the choices made in respect of the planetary boundary layer and land
surface schemes in the mesoscale model to produce the meteorological forecast thereby leading to certain amount of uncertainty
in the resultant concentrations. Results show that the specific choices made about the atmospheric model configuration can
significantly after the simulated concentrations. 相似文献
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D. A. Plummer J. C. McConnell L. Neary J. Kominski R. Benoit J. Drummond J. Narayan V. Young D. R. Hastie 《Atmospheric environment (Oxford, England : 1994)》2001,35(36):240
An aircraft-based measurement campaign was conducted during the summer of 1996 in the vicinity of Toronto, Canada. The objective of the campaign was to assess the errors in a particular emission inventory used by three-dimensional air quality models. Measurements of NO2 and hydrocarbons were made both upwind and downwind of Toronto, on days with strong synoptic-scale flow from a west to northerly direction. The chemical composition of the background airmass on these days was typical of unpolluted continental air. Measurements have been compared with the output from an on-line air quality model (MC2-AQ) run at 5 km resolution and suggest that emissions of NOx from Toronto are well described in the emission database, though evidence that NOx emissions are underestimated for suburban regions surrounding Toronto was found. In general, no significant underestimation of hydrocarbon emissions was found, though emissions of the model propane species, which includes acetylene and benzene, was underestimated by at least a factor of two. 相似文献
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Humphrey O. S. Young S. D. Bailey E. H. Crout N. M. J. Ander E. L. Hamilton E. M. Watts M. J. 《Environmental geochemistry and health》2019,41(5):2145-2156
Environmental Geochemistry and Health - Iodine is an essential micronutrient for human health; phytofortification is a means of improving humans’ nutritional iodine status. However, knowledge... 相似文献