We studied the effect of cattle grazing on shoot density and flux in 4 southwest Montana beaked sedge (Carex rostrato ex With.) stands for 2 years. Forty plots were protected and 40 plots were grazed by cattle in June and September of 1989 and 1990. The effect of grazing vs. no grazing on mean shoot density and emergence varied over time (treatment by time interactionP

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<p><strong>Abstract.</strong> Wind extraction from stratospheric ozone (O<sub>3</sub>) assimilation is examined using a hybrid ensemble 4DVar shallow water model (SWM) system coupled to the tracer advection equation. Stratospheric radiance observations are simulated using global observations of the SWM fluid height (<i>Z</i>), while O<sub>3</sub> observations represent sampling by a typical polar-orbiting satellite. Four ensemble sizes were examined (25, 50, 100, and 1518 members), with the largest ensemble equal to the number of dynamical state variables. The optimal length scale for ensemble localization was found by tuning an ensemble Kalman filter (EnKF). This scale was then used for localizing the ensemble covariances that were blended with conventional covariances in the hybrid 4DVar experiments. Both optimal length scale and optimal blending coefficient increase with ensemble size, with optimal blending coefficients varying from 0.2 to 0.5 for small ensembles to 0.5 to 1.0 for large ensembles. The hybrid system outperforms conventional 4DVar for all ensemble sizes, while for large ensembles the hybrid produces similar results to the offline EnKF. Assimilating O<sub>3</sub> in addition to <i>Z</i> benefits the winds in the hybrid system, with the fractional improvement in global vector wind increasing from ~35 % with 25 and 50 members to ~50 % with 1518 members. For the smallest ensembles (25 and 50 members), the hybrid 4DVar assimilation improves the zonal wind analysis over conventional 4DVar in the Northern Hemisphere (winter-like) region and also at the equator, where <i>Z</i> observations alone have difficulty constraining winds due to lack of geostrophy. For larger ensembles (100 and 1518 members), the hybrid system results in both zonal and meridional wind error reductions, relative to 4DVar, across the globe.</p>

Abstract.Extraction of wind and temperature information from stratospheric ozone assimilation is examined within the context of the Navy Global Environmental Model (NAVGEM) hybrid 4D-Var data assimilation (DA) system. Ozone can improve the winds and temperatures through the two different DA mechanisms. First, through the "flow-of-the-day" ensemble background error covariances that are blended together with the static background error covariance. Second, via the ozone continuity equation 5 in the tangent linear model and adjoint used for minimizing the cost function. All experiments assimilate actual conventional data and satellite-derived wind vectors in order to maintain nearly the same realistic troposphere. In the stratosphere, the experiments assimilate simulated ozone and/or radiance observations in various combinations. The simulated observations are taken from a 16-day truth experiment (TE), which is an analysis with no stratospheric observations. The impact of ozone on the analysis is evaluated by comparing the experiments to the TE. Ozone assimilation is found to benefit the winds and 10 temperatures when data are of sufficient quality and frequency. For example, global hourly ozone data with no error constrains the stratospheric winds and temperature to within ~2 ms -1 and ~1 K, respectively. This demonstrates that there is dynamical information in the ozone distribution that can potentially be used to improve the stratosphere. This is particularly important for the tropics, where radiance observations have difficulty constraining winds due to their broad weighting functions and breakdown of geostrophic balance. Global ozone assimilation provides the largest benefit when the hybrid blending coefficient 15 is an intermediate value (0.5 was used in this study), rather than 0.0 (no ensemble background error covariances) or 1.0 (no static background error covariances), which is consistent with other hybrid DA studies. Reduction of the ozone sampling frequency, addition of observational noise, or inclusion of radiance observations all reduce the benefit of ozone. For example, a single polar-orbiting ozone measurement set with realistic errors has no significant impact on the wind analysis when a full suite of radiance observations is also assimilated. An examination of cross-correlations between ozone and other variables 20shows that a single ozone observation behaves like a potential vorticity (PV) "charge", or a monopole of PV, with rotation about a vertical axis and vertically oriented temperature dipole. Further understanding of this relationship may help in designing observation systems that would optimize the impact of ozone on the dynamics.

Unusual structures, most forming depressions but some domes, occur on the clay flats along the west and northeast shores of Great Salt Lake. They are submerged by the present high water levels (1975) but were exposed at the time of previous studies (1960-1961 and 1971 ). Trenches cutting the structures in cross section and cores taken within and around the structures reveal a variety of forms in layered and contorted clays and unconsolidated silts, sands, oolites, gypsum, and gypsum crystals. Information obtained by Stifel (1964) and by this study is not sufficient or definitive enough to explain the origin of these un usual and puzzling structures. Their origin is open to speculation. Techniques for obtaining peel samples of trench walls are described in detail.