1. Electrified Simulations of Hurricane Rita (2005) with Comparisons to LASA Data Steve Guimond 1,2, Jon Reisner 2, Chris Jeffery 2 and Xuan-Min Shao 2 1 Florida State University 2 Los Alamos National Laboratory

2. Motivation Improve understanding and forecasting of TC intensification

3. Latent Heat Updraft Background Vortex Microphysics Hurricane Intensification Roadmap Eddy Heat and Momentum Fluxes Balanced response Adjustment Symmetric heating Asymmetric heating Adjustment Balanced response Adjustment Intensity and Structure Change Nolan and Grasso (2003)

4. Motivation Improve understanding and forecasting of TC intensification –Convective obs hard to come by over ocean Doppler radar coverage very sparse Lightning fills gaps in convective monitoring ?

5. Latent Heat Updraft Background Vortex Microphysics Hurricane Intensification Roadmap Eddy Heat and Momentum Fluxes Balanced response Adjustment Symmetric heating Asymmetric heating Adjustment Balanced response Adjustment Intensity and Structure Change Nolan and Grasso (2003) Lightning Collisions & Charging

6. Motivation Improve understanding and forecasting of TC intensification –Convective obs hard to come by over ocean Doppler radar coverage very sparse Lightning fills gaps in convective monitoring ? –Understand relationship between latent heating and lightning –When/where to add energy to system

7. New Research Tools –Observational component Los Alamos Sferic Array (LASA; Shao et al. 2000) –Existing VLF/LF array »Records full EMP (allows detection of intracloud and cloud- to-ground strokes) »Lat/Lon, time New Dual VLF-VHF 4-D lightning mapping array –Deployed along banks of Gulf of Mexico –VLF (~2000 km range) –VHF (~500 km range) »Provides precise height retrieval

8. New Research Tools –Theoretical component Advanced atmospheric model HIGRAD (Reisner et al. 2005) –Compressible Navier-Stokes, non-hydrostatic, bulk or explicit microphysics –Differentiable (smooth) numerics with greatly reduced time errors (option) Coupled to electrification model (Mansell et al. 2005) –Non-inductive collisional charge separation (Saunders) –Lightning discharge model requires significant tuning »Flash initiated when EF exceeds “floor” »What is a good “floor” for hurricanes? »Limit “floor” to ~50 kV/m for reasonable results

9. Do Eyewall Hot Towers Produce Lightning? Next slides… –ER-2 Doppler Radar observations of Hot Towers Linear Depolarization Ratio (LDR) –particle canting angle or asymmetry –dielectric constant (i.e. wet or dry) Retrieved vertical velocities (nadir beam) –Lightning Instrument Package (LIP) Aircraft (20 km) electric field mills (x,y,z components) ~1 s sampling, ~200 m horizontal resolution

10. Hot Tower #1: CAT 2 Dennis (2005) -8 to -15 dB  large, wet, asymmetric ice to large, wet snow aggregates -13 to -17 dB  medium, wet graupel or small hail -18 to -26 dB  small, dry ice particles to dry, low density snow

11. Hot Tower #2: CAT 4 Emily (2005) -8 to -15 dB  large, wet, asymmetric ice to large, wet snow aggregates -13 to -17 dB  medium, wet graupel or small hail -18 to -26 dB  small, dry ice particles to dry, low density snow

12. Hurricane Rita Simulations Current configuration –Grid 1,980 km on a side; 4 km inner mesh, stretch to 20 km 35 m stretching to 15 km –Relaxation boundary conditions –Weak, top gravity wave absorber –F plane Initialization procedure –Barotropic vortex, max wind of 40 m/s –Initialize mass from Key West 88D reflectivity Storm-centered, gridded, native 1 km Below melting  rainwater  saturate lower levels Above melting  graupel or snow  hydrometeor drag, phase changes –Gaussian water vapor function from eyewall to ~200 km radius –ECMWF operational analyses for large scale –Satellite SSTs, High-res topography 3 Hours Into Simulation

13. HIGRAD vs. LASA Model Observations

14. Initializing with LASA data Rainwater mixing ratio

15. Potentially relevant work Understand the non-linear response of observed vortices to retrieved heating –Airborne Dual-Doppler Radar: Hurricane Guillermo (1997) –Latent heat retrieval (Guimond 2008) What spatial/temporal scales of heating does the hurricane “feel” ? –Balanced adjustment at 100 m vs. 2 km –Are small scale details of lightning necessary to capture intensification? Governed by model grid cells Is bulk heating sufficient?

16. P-3 EDOP

17. New area of research with physics not well understood –Not all deep convection is created equal –Lightning discharge processes? How to correctly initialize hurricane? –Radar is good, but impractical –Use LANL data (initialization and assimilation) –How is lightning tied to latent heating? Comparisons shed light on future simulations –Need broader wind field –Need better rainband initialization –Beta plane Conclusions and Future Work

18. Acknowledgments LANL Hurricane Lightning Team References Reisner et al. (2005) Mansell et al. (2005) Molinari et al. (1999) Squires and Businger (2008)

19. Some Model Results 4 hours into simulation Cloud Liquid Water (g/kg) Vertical Velocity (m/s) Graupel (g/kg) Ice (g/kg)