Ünlü, Kahraman
Unsaturated hydraulic conductivity K values as a function of soil‐water pressure head h were measured in the soil at 75 cm depth at 70 different sites separated from one another by a distance of l m along a horizontal transect. K field was viewed as a random function of spatial location x. Field data were analyzed (1) to examine the isotropy and stationarity of K, (2) to check the ergodicity of K in the mean and covariance functions, and (3) to characterize the distribution properties of K by estimating the higher‐order correlations, that is, third and fourth cumulants. The mean functions were estimated by averaging over h and x. The covariance function was studied to investigate its spatial origin dependency. Logs and square roots of K were used for estimating the third and fourth cumulants. Results showed that spatial covariance functions are anisotropic and both lag and origin dependent, that is, spatially nonhomogeneous. Because the stationarity (statistical homogeneity) of K is scale dependent, which was indicated by the identification of locally stationary covariance regions, the ergodic properties of K are also scale dependent at smaller spatial scales. Results related to the distribution characteristics of K indicated that although ln K is marginally Gaussian distributed, in the context of spatial stochastic processes the random field of ln K is not Gaussian because the third and fourth cumulants of the field are still significantly different from zero and have the same order of magnitude as the first and second cumulants. The square root transformation, however, resulted in a random field that is approximately Gaussian although marginal distributions of urn:x-wiley:00431397:media:wrcr4956:wrcr4956-math-0001 remained skewed. Analyses of ln K and urn:x-wiley:00431397:media:wrcr4956:wrcr4956-math-0001 indicated that better transformations which would result in both marginal and joint Gaussian behavior for the random field of K are needed.


Accuracy assessment of MODIS daily snow albedo retrievals with in situ measurements in Karasu basin, Turkey
Tekeli, AE; Sensoy, A; Sorman, A; Akyürek, Sevda Zuhal; Sorman, U (Wiley, 2006-03-15)
Over the ablation period of 2004, daily snow albedo values retrieved from the moderate-resolution imaging spectroradiometer (MODIS) Terra were compared with ground-based albedo measurements. Two data sets are used for this study. The first data set is from two automatic weather stations (AWS) located at fixed points in Karasu basin in eastern Turkey. This provided the temporal assessment of MODIS daily snow albedo values. The second data set, consisting of 19 observation points randomly distributed around o...
Modeling biogeochemical processes in subterranean estuaries: Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients
Spiteri, Claudette; Slomp, Caroline P.; Tuncay, Kağan; Meile, Christof (American Geophysical Union (AGU), 2008-02-22)
[1] A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO(3)(-), NH(4)(+), and PO(4)) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater-seawater mixing zone determine the extent of nutrient ...
The structure of turbulent flow in an open channel bend of strong curvature with deformed bed: Insight provided by detached eddy simulation
Constantinescu, George; Köken, Mete; Zeng, Jie (American Geophysical Union (AGU), 2011-05-12)
[1] Results of a detached eddy simulation (DES) are used to better understand the effects of the mean flow three-dimensionality and secondary currents on turbulence and boundary shear stresses and the mechanisms through which the momentum and Reynolds stresses are redistributed in a strongly curved 193 degrees bend with fixed deformed bed corresponding to the later stages of the erosion and sedimentation process. The ratio between the radius of curvature of the curved reach and the channel width is close to...
Rise velocity of an air bubble in porous media: Theoretical studies
Corapcioglu, MY; Cihan, A; Drazenovic, M (American Geophysical Union (AGU), 2004-04-29)
[1] The rise velocity of injected air phase from the injection point toward the vadose zone is a critical factor in in-situ air sparging operations. It has been reported in the literature that air injected into saturated gravel rises as discrete air bubbles in bubbly flow of air phase. The objective of this study is to develop a quantitative technique to estimate the rise velocity of an air bubble in coarse porous media. The model is based on the macroscopic balance equation for forces acting on a bubble ri...
Comparison of prognostic and diagnostic surface flux modeling approaches over the Nile River basin
Yılmaz, Mustafa Tuğrul; Zaitchik, Ben; Hain, Chris R.; Crow, Wade T.; Ozdogan, Mutlu; Chun, Jong Ahn; Evans, Jason (American Geophysical Union (AGU), 2014-01-01)
Regional evapotranspiration (ET) can be estimated using diagnostic remote sensing models, generally based on principles of energy balance closure, or with spatially distributed prognostic models that simultaneously balance both energy and water budgets over landscapes using predictive equations for land surface temperature and moisture states. Each modeling approach has complementary advantages and disadvantages, and in combination they can be used to obtain more accurate ET estimates over a variety of land...
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