An ensemble Kalman filter–variational hybrid data assimilation system based on the gridpoint statistical interpolation (GSI) three-dimensional variational data assimilation (3DVar) system was developed. The performance of the system was investigated using the National Centers for Environmental Prediction (NCEP) Global Forecast System model. Experiments covered a 6-week Northern Hemisphere winter period. Both the control and ensemble forecasts were run at the same, reduced resolution. Operational conventional and satellite observations along with an 80-member ensemble were used. Various configurations of the system including one- or two-way couplings, with zero or nonzero weights on the static covariance, were intercompared and compared with the GSI 3DVar system. It was found that the hybrid system produced more skillful forecasts than the GSI 3DVar system. The inclusion of a static component in the background-error covariance and recentering the analysis ensemble around the variational analysis did not improve the forecast skill beyond the one-way coupled system with zero weights on the static covariance. The one-way coupled system with zero static covariances produced more skillful wind forecasts averaged over the globe than the EnKF at the 1–5-day lead times and more skillful temperature forecasts than the EnKF at the 5-day lead time. Sensitivity tests indicated that the difference may be due to the use of the tangent linear normal mode constraint in the variational system. For the first outer loop, the hybrid system showed a slightly slower (faster) convergence rate at early (later) iterations than the GSI 3DVar system. For the second outer loop, the hybrid system showed a faster convergence.

The maximum voluntary range of motion (ROM) of the major joints of the upper body was studied in a seated position and compared between young and elderly subjects. A total of 41 subjects (22 young male and female subjects aged 25 to 35 years, 19 elderly male and female subjects aged 65 to 80 years) took part in the experiment. In total, 13 maximum voluntary joint motions were performed by each subject. Age was found to have a non-uniform effect on the ROM of the joints investigated in this study. Its effect on ROM was joint specific and motion specific. The highest loss in ROM was observed in the neck and trunk, especially for neck extension, lateral flexion and axial rotation as well as for trunk lateral flexion and axial rotation. No significant age differences were observed in the elbow and wrist joint ROMs. The effect of gender on joint ROM was much weaker than that of age. Only four among the 26 joint ROMs investigated in this study were significantly different between the two gender groups.

A GSI-based EnVar data assimilation system is extended to directly assimilate radar reflectivity to initialize convective-scale forecasts. When hydrometeor mixing ratios are used as state variables (method mixing ratio), large differences of the cost function gradients with respect to the small hydrometeor mixing ratios and wind prevent efficient convergence. Using logarithmic mixing ratios as state variables (method logarithm) fixes this problem, but generates spuriously large hydrometeor increments partly due to the transform to and from the logarithmic space. The tangent linear of the reflectivity operators further contributes to spuriously small and large hydrometeor increments in method mixing ratio and method logarithm, respectively. A new method is proposed by directly adding the reflectivity as a state variable (method dBZ). Without the tangent linear and adjoint of the nonlinear operator, the new method therefore avoids the aforementioned problems. The newly proposed method is examined on the analysis and prediction of the 8 May 2003 Oklahoma City tornadic supercell storm. Both the probabilistic forecast of strong low-level vorticity and maintenance of strong updraft and vorticity in method dBZ are more consistent with reality than in method logarithm and method mixing ratio. Detailed diagnostics suggest that a more realistic cold pool due to the better analyzed hydrometeors in method dBZ than in other methods leads to constructive interaction between the surface gust front and the updraft aloft associated with the midlevel mesocyclone. Similar low-level vorticity forecast and maintenance of the storm are produced by the WSM6 and Thompson microphysics schemes in method dBZ. The Thompson scheme matches the reflectivity distribution with the observations better for all lead times, but shows more southeastward track bias compared to the WSM6 scheme.

Forecasts generated by the Center for Analysis and Prediction of Storms with 1- and 4-km grid spacing using the Advanced Research Weather Research and Forecasting Model (ARW-WRF; ARW1 and ARW4, respectively) for the 2009–11 NOAA Hazardous Weather Testbed Spring Experiments are compared and verified. Object-based measures, including average values of object attributes, the object-based threat score (OTS), and the median of maximum interest (MMI) are used for the verification. Verification was first performed against observations at scales resolvable by each forecast model and then performed at scales resolvable by both models by remapping ARW1 to the ARW4 grid (ARW1to4). Thirty-hour forecasts of 1-h accumulated precipitation initialized at 0000 UTC on 22, 36, and 33 days during the spring of 2009, 2010, and 2011, respectively, are evaluated over a domain covering most of the central and eastern United States. ARW1, ARW1to4, and ARW4 all significantly overforecasted the number of objects during diurnal convection maxima. The overforecasts by ARW1 and ARW1to4 were more pronounced than ARW4 during the first convection maximum at 1-h lead time. The average object area and aspect ratio were closer to observations for ARW1 and ARW1to4 than for ARW4. None of the models showed a significant advantage over the others for average orientation angle and centroid location. Increased accuracy for ARW1, compared to ARW4, was statistically significant for the MMI but not the OTS. However, ARW1to4 had similar MMI and OTS as ARW4 at most lead times. These results are consistent with subjective evaluations that the greatest impact of grid spacing is on the smallest resolvable objects.