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[1] Comprehensive measurements of the water table response to simple harmonic forcing at the base of a sand column are presented and discussed. In similar experiments, Nielsen and Perrochet (2000) observed that fluctuations in the total moisture were both damped and lagged relative to the water table fluctuations. As a result, the concept of a complex effective porosity was proposed as a convenient means to account for the damping and phase lag through its magnitude and argument, respectively. The complex effective porosity then enables simple analytical solutions for the water table (and total moisture) dynamics including hysteresis. In this paper, these previous experiments are extended to cover a wider range of oscillation frequencies and are conducted for three well-sorted materials with median grain diameters of 0.082, 0.2, and 0.78 mm, respectively. In agreement with existing theory, the influence of the capillary fringe is shown to increase with the oscillation frequency. However, the complex effective porosity model corresponding to the classical Green and Ampt (1911) capillary tube approximations is shown to be inadequate when compared to the data. These limitations are overcome by the provision of an empirical, frequency-dependent complex effective porosity model fit to the data. Using measured moisture retention parameters, numerical simulation of the data solving a nonhysteretic van Genuchten-Richards' equation type model is unable to replicate the observations. Existing results of a hysteretic numerical model are shown to be in good agreement with the extended database.Citation: Cartwright, N., P. Nielsen, and P. Perrochet (2005), Influence of capillarity on a simple harmonic oscillating water table: Sand column experiments and modeling, Water Resour. Res., 41, W08416,

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Understanding anticipated climate-induced changes in the global wind-wave climate is paramount for sustainable development of coastal and ocean industry-operations, resources, ecosystems and for the mitigation of potential impacts on coastal settlements. Intensive research has been placed into global and regional wave climate projections over the past 10 years, but no systematic review has been conducted to date. Here, we present a consensus-based analysis of 91 published global and regional scale wind-wave climate projection studies to establish consistent patterns of impacts of global warming on the wind-wave climate across the globe. Furthermore, we critically discuss research efforts, current limitations and identify opportunities within the existing community ensemble of projections to resolve various sources of uncertainty amongst the sparsely sampled set of future scenarios. We find consensus amongst studies regarding an increase of the mean significant wave height ̅ s across the Southern Ocean, tropical eastern Pacific and Baltic Sea, and conversely, a decrease of ̅ s over the North Atlantic and Mediterranean Sea. Furthermore, we observe that projections of ̅ s over the eastern north Pacific and southern Indian and Atlantic Oceans lack consensus. Similarly, future projections of extreme s lack consensus everywhere, except for the Southern Ocean and North Atlantic. We note a distinct lack of research regarding projected

[1] Comprehensive measurements are presented of the piezometric head in an unconfined aquifer during steady, simple harmonic oscillations driven by a hydrostatic clear water reservoir through a vertical interface. The results are analyzed and used to test existing hydrostatic and nonhydrostatic, small-amplitude theories along with capillary fringe effects. As expected, the amplitude of the water table wave decays exponentially. However, the decay rates and phase lags indicate the influence of both vertical flow and capillary effects. The capillary effects are reconciled with observations of water table oscillations in a sand column with the same sand. The effects of vertical flows and the corresponding nonhydrostatic pressure are reasonably well described by small-amplitude theory for water table waves in finite depth aquifers. That includes the oscillation amplitudes being greater at the bottom than at the top and the phase lead of the bottom compared with the top. The main problems with respect to interpreting the measurements through existing theory relate to the complicated boundary condition at the interface between the driving head reservoir and the aquifer. That is, the small-amplitude, finite depth expansion solution, which matches a hydrostatic boundary condition between the bottom and the mean driving head level, is unrealistic with respect to the pressure variation above this level. Hence it cannot describe the finer details of the multiple mode behavior close to the driving head boundary. The mean water table height initially increases with distance from the forcing boundary but then decreases again, and its asymptotic value is considerably smaller than that previously predicted for finite depth aquifers without capillary effects. Just as the mean water table over-height is smaller than predicted by capillarity-free shallow aquifer models, so is the amplitude of the second harmonic. In fact, there is no indication of extra second harmonics (in addition to that contained in the driving head) being generated at the interface or in the interior.

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This paper presents a sand column dataset on the soil moisture-pressure dynamics above a simple harmonic oscillating water table. A total of 19 experiments were conducted in which all experimental parameters were held constant except for the oscillation period which ranged between 12.25 hours down to 10 seconds. The data show clear evidence of hysteresis at longer oscillation periods where the unsaturated zone has sufficient time to adjust to the water table motion. At shorter periods the contrary exists with the extent of moisture-pressure variations greatly reduced and, for periods less than 15 minutes, the dynamics become nonhysteretic. The high frequency moisture-pressure loops, although non-hysteretic, do not follow the (non-hysteretic) static equilibrium wetting or drying curves but are consistent with the scanning loops generated by a commonly adopted hysteresis algorithm for numerical solution of the Richards (1931) equation. Thus, the data provides new physical insights behind the need to include hysteresis effects when simulating high frequency water table motions as found by previous researchers.