How Well are Tropical Cyclones Represented in Reanalysis Data Sets?

Tropical cyclones (TCs) are identified and tracked in six recent reanalysis data sets and compared with those from the IBTrACS best track archive. Results indicate that nearly every cyclone present in IBTrACS over the period 1979-2012 can be found in all six reanalyses using a tracking and matching approach. However, TC intensities are significantly under-represented in the reanalyses compared to the observations. Applying a typical objective TC identification scheme, it is found that the largest uncertainties in TC identification occur for the weaker storms; this is exacerbated by uncertainties in the observations for weak storms and lack of consistency in operational procedures. For example, it is unclear whether certain types of storms, such as tropical depressions, subtropical cyclones and monsoon depressions, are included in the best track data for all reporting agencies. There are definite improvements in how well TCs are represented in more recent, higher resolution reanalyses; in particular MERRA2 is comparable with the NCEP-CFSR and JRA55 reanalyses, which perform significantly better than the older MERRA reanalysis. 12