1. WWOSC 2014
Thursday, August 21, 2014
Montreal, Canada
Advancing Microphysics Parameterizations in the Hurricane Weather Research and Forecasting (HWRF) System
Christina Holt1,2,3, Ligia Bernardet1,2,3, Mrinal Biswas1,4 1Developmental Testbed Center
2NOAA ESRL Global Systems Division, Boulder CO
3University of Colorado CIRES , Boulder CO
4National Center for Atmospheric Research, Boulder, CO
Acknowledgements:
Rob Fovell, UCLA

2. Outline The role of the DTC The Community HWRF
Implementation tests performed at DTC
Current collaboration with research community
Ongoing & preliminary findings
Future work 2

3. The Developmental Testbed Center
…is a distributed facility (NCAR and NOAA) where the NWP community can test and evaluate models and techniques for use in research and operations
DTC’s Goals
Link Research and Operational Communities
Speed transition of research results in operations
Accelerate improvement in NWP
Develop and test promising new NWP techniques
Provide an opportunity for NWP community to perform cycled tests of model and data assimilation systems 3

4. DTC Strategies to promote HWRF R2O
Code Management
Create and sustain a framework for NCEP and the research community to collaborate and keep HWRF code unified
User and developer support
Support the community in using an operational hurricane model
DTC Visitor Program – some approved projects involving HWRF
Development of an HWRF diagnostics module to evaluate intensity and structure using synthetic flight paths through tropical cyclones (J. Vigh - NCAR)
Diagnosing tropical cyclone motion forecast errors in HWRF (T. Galarneau - NCAR)
Improving HWRF track and intensity forecasts via model physics evaluation and tuning (R. Fovell - UCLA)
Evaluation of two HWRF microphysics/radiation configurations with remote-sensing data (S. Bao – CCU)
Testing and Evaluation
Perform tests to assure integrity of community code and evaluate new developments for potential operational implementation 4

5. HWRF: NOAA operational hurricane model
HWRF Components
WRF-NMM model (NMM)
Pre-Processor (WPS and prep_hybrid)
Vortex improvement
Data assimilation (Gridpoint Statistical Interpolation)
Coupler (NCEP)
Ocean (Princeton Ocean Model for Tropical Cyclones-TC)
Post-Processor (UPP)
Vortex Tracker (GFDL)
POM-TC
Atmospheric preprocessors
Ocean initialization
Post processing
Vortex tracker
NCEP
coupler
Vortex
initialization
WRF
atmosphere
GSI
Community version released each year in August
Reflects the current year’s operational HWRF capabilities 5

6. HWRF v3.5a Atmospheric Configuration
Introduced an empirical scaling factor, gfs_alpha, that reduces mixing by limiting the momentum eddy viscosity
POM-TC
3 km
9 km
Introduced an empirical dependency of BL height on Critical Richardson Number
27 km
Physics
Parameterization
Cumulus (d01 and d02)
Simplified Arakawa Schubert with shallow convection
Microphysics
Ferrier for the tropics
Planetary Boundary Layer
GFS (Hong and Pan 1996,Vickers and Mahrt 2004, Gopal et al 2013) (90:90:30 s)
Surface Layer
GFDL (modified)
Land Surface Model
GFDL slab model
Radiation
GFDL (60:60:60 min)

7. HWRF T&E: Thompson/RRTMG
Thompson vs. Ferrier
RRTMG vs. GFDL
Advects individual species
Advects total condensate
Partial Double Moment
Single Moment
6-classes w/ graupel
Cloud, rain, and snow
Coupled with RRTMG
(mixing ratio & concentration)
Supplies only MR to radiation scheme
Tested for HWRF:
red. int. bias at long lead times in ATL
Used in Operational HWRF
Uses internal assumptions to compute concentrations given MR
Uses assumptions consistent with Thompson to compute concentrations given MR
Interacts with clouds
Interacts with clouds*
Tested for HWRF:
red. int. bias at long lead times in the ATL
Used in Operational HWRF
* Inconsistencies between Ferrier and GFDL radiation: clouds too transparent to radiation
-Rob Fovell, UCLA, HFIP Participant
Thompson mp for Hurricane Sandy improved track forecasts
-A. Chakraborty, India CAOS, NCAR/RAL visitor
DTC: Coupling of the Thompson with RRTMG 7

8. Track error Intensity Bias North Atlantic Eastern North Pacific
T/RRTMG
F/GFDL
Track error
T/RRTMG improves track for AL but degrades for EP
North Atlantic
Eastern North Pacific
Intensity Bias
In 2013, the DTC ran a test changing the microphysics and radiation to T/RRTMG over several hundred cases in both the ATL and EP and found that, although we expected improvement from the more physical parameterizations, there were degradations in the track and creation of a negative intensity bias in the EP. This became the focus of a case study at the DTC and for visiting scientists.
T/RRTMG increases intensity for shorter lead times, decreases for longer lead times
T/RRTMG creates negative intensity bias in EP 8

9. Case study: Daniel 04E
Thompson too fast and northward; reason under investigation
Ferrier runs similar at 5-day lead time
Bulk statistics for Daniel 04E and case study show that Thompson takes track to N
Storms are in area of strong SST gradient
Northern tracks leads to cool SST under storm and low bias
SST (C) 9

10. DTC VSP: Rob Fovell and Peggy Bu, UCLA
HWRF’s GFDL radiation scheme is deficient with respect to cloud-radiative forcing (CRF)… see Bu et al. (2014)
With proper CRF, the horizontal extent of the near surface wind field increases
Storms with larger wind fields advect more planetary vorticity northward (beta drift) and move faster
Westerly moving storms pull northward, and are ahead of the observed storm
Working Hypotheses:
CRF and gfs_alpha work together to broaden the wind field too much, causing increased beta drift northward
Once the storms are over cold water to the north, they lose intensity

11. Results from DTC visit Courtesy of Rob Fovell
T/RRTMG has broader/weaker storm
T/RRTMG has narrower/weaker storm
F/RRTMG has slightly weaker, broader storm
72-96 hr
30-36 hr
gfs_alpha = 0.7 11

12. New DTC Physics Experiments
Series of forecasts started from the same initial conditions using HWRF v3.5a
Varying microphysics scheme and gfs_alpha
Assess storm size and track changes
Are the forecasts with real storm settings consistent with the working hypotheses from the ideal studies?
gfs_alpha
Microphysics
Radiation
0.7
Ferrier
GFDL
0.4
Thompson
RRTMG

13. Storm Tracks for Daniel (EP 2012)
Thompson 0.4
Thompson 0.7
Ferrier 0.4
Ferrier 0.7
Ferrier/GFDL/0.7
Best Track
Tracks diverge around 60 hrs
Thompson fcsts take a northward track
gfs_alpha = 0.4 has a more accurate track
Ferrier is less sensitive to gfs_alpha

14. Average Radial Velocity
Averaged over first 60 hrs
Averaged over hrs
Thompson 0.4
Thompson 0.7
Ferrier 0.4
Ferrier 0.7
Ferrier/GFDL/0.7
Observed

15. Summary
The findings in the real case study reflect the idealized findings obtained by DTC Visiting Scientists
CRF + larger gfs_alpha broaden the wind field at shorter lead times
Broader wind field (all else equal) leads to northward track
Investigation of other factors is needed to determine the intensity/size relationships with physics
Further testing would be necessary to identify potential alternatives for operational implementation
Rapid Radiative Transfer Model - Global

16. Moving forward DTC will continue to work with visiting scientists
Assess the impact of gfs_alpha, radiation, and microphysics combinations on forecasts
Provide resources to assess the potential for future R20
Look at radiation budgets, and the sensitivity of track, intensity, and structure to CRF
Community Support by DTC
Model freely available and supported
Upcoming release this month
2014 operational capability
Idealized capability
Support for all basins
Unified Python scripts with EMC
Improved model for 2014
Updated moving nests, ocean, and initialization improved forecast
Opened opportunities for major future developments
Ongoing development
Framework: multiple moving nests
Physics for high-resolution
LSM, storm surge, inundation
DA / Initialization