Historical Hurricanes in MERRA-2

Tropical cyclones were not detected in global scale analyses until the 1990s. The initialization problem was a major hindrance in hurricane forecasting. Artificial enhancements of the cyclone circulation e.g., the `bogus vortex', were commonly used, even when initializing multiply-nested regional models at horizontal resolutions which should have allowed for a representation of a hurricane structure. Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), offers an unprecedented view of `historical hurricanes' occurred in the years between 1979 and 1989. The assimilation of existing observations with a modern data assimilation system reveals that most of the hurricanes observed in those years can indeed be represented in global analyses. While the tropical cyclone fine structure cannot be solved and intensity is obviously underestimated at the resolution of MERRA-2, a very clear `signature' of the tropical cyclone with center pressures down to 950 hPa, vertical aligned structure, strong warm core, and wind maxima exceeding 40 m/s can nevertheless be detected, fully consistent with the large-scale environment. Examples from infamous hurricanes such as David (1979), Frederic (1979), Allen (1980), Gloria (1985), and Gilbert (1988) will be provided. MERRA-2 provides an enormous improvement not only with respect to operational analyses of the time, but also with respect to contemporary reanalyses, thus establishing a solid starting point for downscaling studies.