1. 1 Application of a Tropical Cyclone Index to Climate Modeling Downscaling Regional Climate Research Section NCAR Earth System Laboratory NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network, the Research Program to Secure Energy for America, and NSF EASM Grant 16045 Greg Holland and Cindy Bruyere Holland WRF Workshop 0612

2. 2 Summary Preamble o A Regional Climate Group o The Hybrid Statistical/Dynamical Approach The Cyclone Genesis Index o History o Climatological Components that do (do not) work o CGI o How to apply Climate Applications Reference Bruyere et al (2012) J. Climate

3. Goes back to Palmen 1948 Gray 1968, 1970 derived first Index All use some combination of moisture, SST and Stability (MPI), and vertical windshear e.g. Emanuel and Nolan (2004): Holland WRF Workshop 0612 3 Genesis Index History

4. Holland WRF Workshop 0612 4 Components that Do/Do not Work Vorticity V. Shear PI RH Observed

5. Holland WRF Workshop 0612 5 Why were RH and Vorticity Included?

6. Holland WRF Workshop 0612 6 The Cyclone Genesis Index

7. Holland WRF Workshop 0612 7 Applying Indices Raw GP

8. Holland WRF Workshop 0612 8 Application to Intense Hurricane Frequency

9. Holland WRF Workshop 0612 9 Climate Applications

10. Holland WRF Workshop 0612 10 Summary Hybrid Statistical/Dynamical Approach is an important (essential) component of regional climate prediction Example: The Cyclone Genesis Index o Can accurately reproduce tropical cyclone and intense hurricane annual frequency variations from coarse reanalyses o Care needs to be taken with content and application method For Climate, when used in combination with high- resolution time-slice simulations the CGI can fill in the gaps and provide a poor-person’s ensemble CGI can provide a quality check on historical archives.