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11.
Representation of agricultural conservation practices with SWAT 总被引：5，自引：0，他引：5
Results of modelling studies for the evaluation of water quality impacts of agricultural conservation practices depend heavily on the numerical procedure used to represent the practices. Herein, a method for the representation of several agricultural conservation practices with the Soil and Water Assessment Tool (SWAT) is developed and evaluated. The representation procedure entails identifying hydrologic and water quality processes that are affected by practice implementation, selecting SWAT parameters that represent the affected processes, performing a sensitivity analysis to ascertain the sensitivity of model outputs to selected parameters, adjusting the selected parameters based on the function of conservation practices, and verifying the reasonableness of the SWAT results. This representation procedure is demonstrated for a case study of a small agricultural watershed in Indiana in the Midwestern USA. The methods developed in the present work can be applied with other watershed models that employ similar underlying equations to represent hydrologic and water quality processes. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
12.
Bernie D. Shizgal 《Astrophysics and Space Science》2007,312(3-4):227-237
The energization of a charged test-particle of mass m in contact with a large ensemble of charged particles of mass M at equilibrium is studied with the Fokker-Planck equation for Coulomb collisions and a quasi-linear diffusion operator for
wave-particle interactions. The features of the nonequilibrium steady state velocity distribution of the test-particle system
is studied as a function of the mass ratio m/M, and the relative strengths of the wave-particle interactions and Coulomb collisions. It is shown that the steady distribution
function is not necessarily a Kappa distribution. The temperature of heavy minor ions given by the model is shown to vary
linearly with the mass ratio as observed in the solar wind. The time evolution of the distribution function with and without
the energization by wave-particle interactions is calculated and it is demonstrated that the Kullback relative entropy rather
than the Tsallis nonextensive entropy rationalizes the results obtained. 相似文献
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14.
D. J. Bernie E. Guilyardi G. Madec J. M. Slingo S. J. Woolnough 《Climate Dynamics》2007,29(6):575-590
The diurnal cycle is a fundamental time scale in the climate system, at which the upper ocean and atmosphere are routinely
observed to vary. Current climate models, however, are not configured to resolve the diurnal cycle in the upper ocean or the
interaction of the ocean and atmosphere on these time scales. This study examines the diurnal cycle of the tropical upper
ocean and its climate impacts. In the present paper, the first of two, a high vertical resolution ocean general circulation
model (OGCM), with modified physics, is developed which is able to resolve the diurnal cycle of sea surface temperature (SST)
and current variability in the upper ocean. It is then validated against a satellite derived parameterization of diurnal SST
variability and in-situ current observations. The model is then used to assess rectification of the intraseasonal SST response
to the Madden–Julian oscillation (MJO) by the diurnal cycle of SST. Across the equatorial Indo-Pacific it is found that the
diurnal cycle increases the intraseasonal SST response to the MJO by around 20%. In the Pacific, the diurnal cycle also modifies
the exchange of momentum between equatorially divergent Ekman currents and the meridionally convergent geostrophic currents
beneath, resulting in a 10% increase in the strength of the Ekman cells and equatorial upwelling. How the thermodynamic and
dynamical impacts of the diurnal cycle effect the mean state, and variability, of the climate system cannot be fully investigated
in the constrained design of ocean-only experiments presented here. The second part of this study, published separately, addresses
the climate impacts of the diurnal cycle in the coupled system by coupling the OGCM developed here to an atmosphere general
circulation model. 相似文献