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81.
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Guleid Artan Hussein Gadain Jodie L. Smith Kwabena Asante Christina J. Bandaragoda James P. Verdin 《Natural Hazards》2007,43(2):167-185
Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated
with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions.
However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling
because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results
from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the
Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling
when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently
with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated.
G. Artan, J. L. Smith and K. Asante – work performed under USGS contract 03CRCN0001. 相似文献
83.
Intercomparison and validation of snow albedo parameterization schemes in climate models 总被引:1,自引:0,他引:1
Snow albedo is known to be crucial for heat exchange at high latitudes and high altitudes, and is also an important parameter
in General Circulation Models (GCMs) because of its strong positive feedback properties. In this study, seven GCM snow albedo
schemes and a multiple linear regression model were intercompared and validated against 59 years of in situ data from Svalbard,
the French Alps and six stations in the former Soviet Union. For each site, the significant meteorological parameters for
modeling the snow albedo were identified by constructing the 95% confidence intervals. The significant parameters were found
to be: temperature, snow depth, positive degree day and a dummy of snow depth, and the multiple linear regression model was
constructed to include these. Overall, the intercomparison showed that the modeled snow albedo varied more than the observed
albedo for all models, and that the albedo was often underestimated. In addition, for several of the models, the snow albedo
decreased at a faster rate or by a greater magnitude during the winter snow metamorphosis than the observed albedo. Both the
temperature dependent schemes and the prognostic schemes showed shortcomings. 相似文献
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85.
Charles I. Scaife Jonathan M. Duncan Laurence Lin Christina Tague Colin D. Bell Lawrence Band 《水文研究》2021,35(9):e14313
The spatial variation of soil moisture over very small areas (<100 m2) can have nonlinear impacts on cycling and flux rates resulting in bias if it is not considered, but measuring this variation is difficult over extensive temporal and spatial scales. Most studies examining spatial variation of soil moisture were conducted at hillslope (0.01 km2) to multi-catchment spatial scales (1000 km2). They found the greatest variation at mid wetness levels and the smallest variation at wet and dry wetness levels forming a concave down relationship. There is growing evidence that concave down relationships formed between spatial variation of soil moisture and average soil moisture are consistent across spatial scales spanning several orders of magnitude, but more research is needed at very small, plot scales (<100 m2). The goal of this study was to characterise spatial variation in shallow soil moisture at the plot scale by relating the mean of measurements collected in a plot to the standard deviation (SD). We combined data from a previous study with thousands of new soil moisture measurements from 212 plots in eight catchments distributed across the US Mid-Atlantic Region to (1) test for a generalisable mean–SD relationship at plot scales, (2) characterise how landcover, land use, season, and hillslope position contribute to differences in mean–SD relationships, and (3) use these generalised mean–SD relationships to quantify their impacts on catchment scale nitrification and denitrification potential. Our study found that 98% of all measurements formed a generalised mean–SD relationship like those observed at hillslope and catchment spatial scales. The remaining 2% of data comprised a mean–SD relationship with greater spatial variation that originated from two riparian plots reported in a previous study. Incorporating the generalised mean–SD relationship into estimates of nitrification and denitrification potential revealed strong bias that was even greater when incorporating mean–SD observations from the two riparian plots with significantly greater spatial variation. 相似文献
86.
The effect of wildfire on peak streamflow and annual water yield has been investigated empirically in numerous studies. The effect of wildfire on baseflow recession rates, in contrast, is not well documented. The objective of this paper was to quantify the effect of wildfire on baseflow recession rates in California for both individual watersheds and for all the study watersheds collectively. Two additional variables, antecedent groundwater storage and potential evapotranspiration, were also investigated for their effect on baseflow recession rates and postfire baseflow recession rate response. Differences between prefire and postfire baseflow recession rates were modeled statistically in 8 watersheds using a mixed statistical model that accounted for fixed and random effects. For the all‐watershed model, antecedent groundwater storage, potential evapotranspiration, and wildfire were each found to be significant controls on baseflow recession rates. Wildfire decreased baseflow recession rates 52.5% (37.6% to 66.0%), implying that postfire reductions in above‐ground vegetation (e.g., decreased interception, decreased evapotranspiration) were a stronger control on baseflow recession rate change than hydrophobicity. At an individual watershed scale, baseflow recession rate response to wildfire was found to be sensitive to intraannual differences in antecedent groundwater storage in 2 watersheds, with the effect of wildfire on baseflow recession rates being greater with lower levels of antecedent groundwater storage. Examination of burn severity for a subset of the study watersheds pointed to riparian zone burn severity as a potential primary control on postfire recession rate change. This study demonstrates that wildfire may have a substantial impact on fluxes to and from groundwater storages, altering the rate at which baseflow recedes. 相似文献
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89.
Galatius A Dietz R Rigét FF Sonne C Kinze CC Lockyer C Bossi R 《Marine pollution bulletin》2011,62(7):1476-1483
Eighty-five stranded or bycaught harbor porpoises collected from the Danish North Sea between 1980 and 2005 were analyzed for perfluorochemicals in the liver. PFOS was the predominant compound, making up on average 88.9% of the ∑PFC, followed by PFOSA (7.8%). PFUnA (1.9%) and PFDA (1.2%) were detected in most samples. PFHxS, PFNA and PFOA were only found in a minority of the samples. We found substantial differences in PFC concentrations among life history stages, the highest concentrations were found in neonates, suckling juveniles and lactating females. Such differences should be considered when PFC levels in wildlife are evaluated. The high concentrations found in young porpoises are of concern as PFCs have known toxic effects on the development of the central nervous system and reproductive organs. Despite efforts to reduce PFC emissions, a decreasing temporal trend of concentrations was not detected for any compound. PFCA concentrations were found to be increasing. 相似文献
90.
Correspondence analysis was applied to 177 chemical analyses (major elements) of rocks from some rhyolitic zones of the Noranda area (Quebec). The objective was to grade the individual sample sections with respect to their attractiveness considering the chemical alterations related to mineralization. The results obtained show that it is possible to differentiate sections from different rhyolitic horizons. 相似文献