Current generation short-range ensemble forecast members tend to be unduly similar to each other, especially for components such as surface temperature and precipitation. One possible cause of this is a lack of perturbations to the land surface state. In this experiment, a two-member ensemble of the Advanced Research Weather Research and Forecasting (WRF) model (ARW) was run from two different soil moisture analyses. One-day forecasts were conducted for six warm-season cases over the central United States with moderate soil moistures, both with explicit convection at 5-km grid spacing and with parameterized convection at 20-km grid spacing. Since changing the convective parameterization has previously been demonstrated to cause significant differences between ensemble forecast members, 20-km simulations were also conducted that were initialized with the same soil moisture but that used two different convective parameterizations as a reference. At 5 km, the forecast differences due to changing the soil moisture were comparable to the differences in 20-km simulations with the same soil moisture but with a different convective parameterization. The differences of 20-km simulations from different soil moistures were occasionally large but typically smaller than the differences from changing the convective parameterization. Thus, perturbing the state of the land surface for this version of WRF/ARW was judged to be likely to increase the spread of warm-season operational short-range ensemble forecasts of precipitation and surface temperature when soil moistures are moderate in value, especially if the ensemble is comprised of high-resolution members with explicit convection.

We are continuing our investigation of the use of stacks of electrically isolated thin metal foils as spectrometers for lost ions from tokamak fusion plasmas. Devices of this type in which the foil thicknesses were a few micrometers were installed on the Joint European Torus during the recent first deuterium–tritium experiment in an effort to observe lost energetic alpha particles. While there was no convincing evidence of lost alpha particles in this experiment, we did observe significant fluxes of low energy (<500 keV) charged particles. In an effort to provide an instrument for the investigation of this phenomenon and of escaping relatively low energy (<100 keV) ions from other fusion plasma devices, we have developed alternative devices with very thin (few hundred nanometers) alternating layers of conductor and insulator. Four such devices have been fabricated and tested for protons with energies between 20 and 160 keV and demonstrated good energy resolution (typically about 10%) for proton bombarding energies between about 40 and 120 keV. One of the devices, consisting of deposited layers of Al, Ti, and SiO2 was operated up to a current density of about 100 m/cm2 at an energy of 100 keV, corresponding to a power volume density of 100 kW/cm3

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An anisotropic prestack depth-migration sequence was used in the imaging of a carbonate accumulation in deep water offshore Brazil. The reservoir is overlain by a complex sequence of evaporites, carbonates, and clastics. Although the latter display a modest magnitude of anisotropy, this parameter has to be taken into account for the depth accuracy required in reservoir evaluation. The seismic data input to the processing consist of two narrow-azimuth streamer surveys, acquired with distinct azimuths that overlap approximately at the center of the reservoir structure. The resulting velocity model is geologically plausible, exhibiting good accuracy when compared with average velocities calculated from check shots and vertical seismic profiles acquired at nearby wells. Such accuracy holds true to the base of the evaporitic sequence, which corresponds roughly to the top of reservoir, and makes this model adequate for depth positioning and hydrocarbon volume calculations. However, deep layers in the velocity models present larger errors and a spatial behavior that does not match geologic expectations. This is attributed to the lack of proper illumination that these conventional seismic acquisitions provide and arguably makes the case for a more modern full-azimuth seismic acquisition over the structure. This limitation is quantified by an illumination map simulated at the top of the reservoir from a waveformmodeling exercise that took into consideration the seismicacquisition parameters over the field.