[1] U-tube measurements of instantaneous velocities, concentrations, and fluxes for a well-sorted, medium-sized sand in oscillatory sheet flow are analyzed. The experiments involved two velocity-asymmetric flows, the same two flows with an opposing current of 0.4 m/s, and a mixed skewed-asymmetric flow, all with a velocity amplitude of 1.2 m/s and flow period of 7 s. We find that the net positive transport rate beneath velocityasymmetric oscillatory flow results from large, but opposing sand fluxes during the positive and negative flow phase. With an increase in velocity asymmetry and, in particular, velocity skewness, the difference in the magnitude of the fluxes in the two half cycles increases, leading to larger net transport rates. This trend is consistent with the observed increase in skewness of the oscillatory bed shear stress. Phase-lag effects, whereby sand stirred during the negative flow phase has not settled by the time of the negative-to-positive flow reversal and is subsequently transported during the positive flow phase, are notable but of minor importance to the net transport rate compared to earlier experiments with finer sands. In the vertical, the oscillatory flux is positive above the noflow bed. Within the sheet flow pick-up layer, the oscillatory flux is negative and similar in magnitude to the positive flux induced by the residual flow. The 0.4 m/s opposing current causes more sand to be picked up during the negative than during the positive flow phase. Above the no-flow bed the resulting negative oscillatory flux is comparable in magnitude to the current-related flux.

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[1] GRAS RO (radio occultations) are validated against co-located ECMWF and COSMIC data and by ECMWF impact trials. We focus on closed-loop data at impact heights above 8 km. Results confirm the high GRAS quality and robustness, showing lower noise than COSMIC and more occultations per day/satellite. Mean differences to ECMWF and COSMIC from 18 km to 35 km show about 0.1% smaller GRAS BAs (bending angles). Around 40 km, ECMWF shows on average about 1% smaller BAs, which may be related to microwave radiances assimilation. Recent ECMWF updates, putting more weight on RO here, reduce this bias. COSMIC co-locations reveal smaller GRAS BAs up to about 50 km, probably partly caused by COSMIC smoothing; this is currently revised. ECMWF forecast trials show similar positive GRAS, COSMIC impacts for Southern latitudes standard deviations, although GRAS provides about 60% fewer occultations. It also demonstrates that more RO instruments are beneficial, particularly for the tropics and Northern latitudes.

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