Bug-fix: WRF hybrid vertical coordinate
- DART now detects whether WRF is using Hybrid Vertical Coordinate (HVC) introduced in WRFv3.9 or terrain following (TF) system. This fix is also compatible with pre WRFv3.9 versions which did not include explicit attribute information for vertical coordinate system. #649
- Improved obs_impact_tool documentation. #571
- citation NCAR -> NSF NCAR #584