A Comparison Between Recent Re-Analysis Data Sets Using Objective Feature Tracking: Storm Tracks and Tropical Easterly Waves.

Data from four recent re-analysis projects (ECMWF, NCEP/NCAR, NCEP/DOE, NASA) have been diagnosed at the scale of synoptic weather systems using an objective feature tracking method. The tracking statistics indicate that overall the re-analyses correspond very well in the Northern Hemisphere (NH) lower troposphere. Differences for the spatial dis-tribution of mean intensities show that the ECMWF re-analysis are systematically stronger in the main storm track regions but weaker around major orographic features. A direct comparison of the track ensembles indicates a number of systems with a broad range of in-tensities which compare well among the re-analyses. In addition, a number of small scale weak systems are found that have no correspondence among the re-analyses or which only correspond upon relaxing the matching criteria indicating possible differences in location and/or temporal coherence. These are distributed throughout the storm tracks, particularly in the regions known for small scale activity such as secondary development regions and the Mediterranean. For the Southern Hemisphere (SH) agreement is found to be generally less consistent i