Holland, Greg, and Cindy Bruyere, National Center for Atmospheric Research
We examine the
application of a Cyclone Genesis Index to both reanalyses and relatively course
climate simulations for assessing potential changes in tropical cyclones. Both
all cyclones and the more intense hurricanes will be examined. We first examine
existing indices and show that several parameters used add no skill for our
purposes. A new CGI is then applied to reanalyses and shown to accurately
reproduce both the mean monthly interannual seasonal variation and the
interannual variability, though care needs to be taken in the selected base
region for application. We find that for assessing basin wide cyclone
frequency, averaging indices over the whole basin is less skillful than is
application to specific regions with high cyclone sensitivity, such as the
Atlantic Main Development region. The applicability of this approach to all
annual tropical cyclones and to just the more intense hurricanes will be
discussed. Future trends from the application to NRCM simulations will also be
described.