Initialization Schemes in the Naval Research
Laboratory’s Tropical Cyclone Prediction Model
(COAMPS-TC)
Eric A. Hendricks1
Melinda S. Peng1
Tim Li2
Xuyang Ge3
1Naval
Research Laboratory (NRL), Monterey, CA, USA
2University of Hawaii and IRPC, Honolulu, HI
3Pennsylvania State University, State College, PA USA
Acknowledgements: Jim Doyle (NRL), Rich Hodur (SAIC), COAMPS-TC group
CMOS 2012 Congress / AMS 21st NWP and 25th WAF Conferences
Montreal, Canada, 29 May-1 June 2012
Introduction
• A crucial part of TC intensity predictions is an accurate and
balanced TC vortex initially
• 3DVAR data assimilation systems usually lack proper
balance constraints suitable for multi-scale TC; rapid
adjustment often occurs after initialization
• A 4D data assimilation system would alleviate the initial
imbalance problem to some degree
• Lack of observational data for TC intensity and structure
remains
What do we do in the mean time?
Hybrid 3DVAR/Dynamic Initialization Schemes have the
possibility of improving the initial balance and storm
intensity/structure, while allowing model physics spin-up,
potentially leading to improved intensity and track forecasts
Dynamic Initialization Schemes: TCDI, DI, TCDI/DI
Application to TC Prediction Using COAMPS-TC
NOGAPS/NCEP analysis
Cold Start
TCDI: Hendricks et al. (2011) WAF,
Zhang et al. (2012) WAF
3DVAR
data assimilation TCDI
Remove TC vortex
TCDI
TCDI/DI
Insert vortex
DI
CNTL
Synthetic TC
obs, Liou and
Sashegy (2011)
Warm Start
Generate vortex
from TCDI
(nudge MSLP)
CNTL: Standard 3DVAR Initialization
DI: 3D Dynamic Initialization to
analysis momentum ua (12-h
relaxation) after 3DVAR
12-h forward DI
𝜕𝑢
𝜕𝑡
= −𝛾(𝑢 − 𝑢𝑎 )
TCDI
TCDI: Tropical Cyclone Dynamic
Initialization (TC component is
dynamic) after 3DVAR
Run forecast model
TCDI/DI: Run TCDI, then run DI
COAMPS-TC Overview
Current and Future Capabilities
Atmospheric Analysis
• Complex Data Quality Control
• Relocation of TC in background
• Synthetic Observations: TC vortex
• NAVDAS 3DVAR: u, v, T, q, TC option
• Initialization: Digital Filter Option
• TC Balance Step: (underway)
Atmospheric Model
• Numerics: Nonhydrostatic, Scheme C,
Moving Nests, Sigma-z, Flexible Lateral BCs
• Physics: PBL, Convection, Explicit Moist
Physics, Radiation, Surface Layer
• TC Tools: Moving nests, dissipative heating,
spray parameterization, shallow convection
Ocean Analysis
• Navy Coupled Ocean Data Assimilation
(NCODA) System
• 2D OI: SST
• 3D MVOI, 3DVAR: T, S, SSH, Ice, Currents
• Complex Data Quality Control
• Initialization: Stability check
Ocean Models
• NRL Coastal Ocean Model (NCOM)
• Numerics: Hydrostatic, Scheme C, Nested
Grids, Hybrid Sigma/z
• Physics: Mellor-Yamada 2.5
• Wave Models (WWIII and SWAN)
• Generalized Coupling Layer (ESMF)
Atmospheric Ensembles
Ocean Ensembles
• Initial Cond. Perturbation: ET, EnKF
• Physics Perturbations: PBL, Convection…
• Lateral BCs: Global ensemble (NOGAPS)
• Probabilistic Products: Intensity, track…
• Initial Cond. Perturbation: ET
• Physics Perturbations: PBL, Fluxes…
• Lateral BCs: NCOM
• Probabilistic Products: Mixed layer, OHC..
The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) is a registered trademark of NRL
COAMPS-TC Control (CNTL) Setup
Dynamics:
Non-hydrostatic, compressible, C-grid (Klemp and
Wilhemson 1978)
Vertical Discretization:
Sigma-z vertical coordinate (40 levels, higher resolution
near sfc)
Grids:
3 nests, 45/15/5-km resolution (2-way nesting), 15/5-km
meshes move with the TC
PBL:
Mellor-Yamada (1.5-order turbulence closure), dissipative
heating (Jin et al. 2007)
Cumulus:
Kain-Fritsch on 45/15-km, shallow convection, explicit
convection on 5-km
Microphysics:
NRL scheme, 6 species, based from Rutledge and Hobbs
1984 & Lin et al. 1983
Radiation:
Fu-Liou scheme
Initialization/DA:
3DVAR scheme (NAVDAS), synthetic observations added
that match observed TC structure and intensity
COAMPS-TC Nest Setup
3 Domains:
45/15/5 km
45 km grid
fixed
Inner 2 grids
(15/5-km)
move with the
TC
DI Case Study: 2011 Hurricane Irene (09L)
2011082518, Cold Start (Domain 3)
10-m Winds (kt)
Sea Level Pressure (hPa)
• During DI, the winds are held quasi-constant
• 3DVAR is not able to produce gradient balanced
vortex, rapid adjustment to winds during DI
2011
IRENE
(09L)
CNTL
DI
TCDI
TCDI/DI
Wind Structure Verification (t=0 h)
10-m Winds (kt)
COAMPS-TC using CNTL
H*WIND
COAMPS-TC using DI
Hurricane
Irene (09L),
2011082512
COAMPS-TC using TCDI/DI
H*WIND
courtesy
NOAA/AOML/
HRD Powell et.
al (2010)
Case Study: 08W (2011) Ma-On
CNTL
JTWC Best Track in black
COAMPS-TC in color
TCDI/DI
10 kt
15 cases
Significant intensity error reductions for Ma-On by using TCDI/DI
Case Study: 07L (2010) Earl
NHC Best Track in black
COAMPS-TC in color
CNTL
TCDI/DI
10 hPa
13 cases
Significant intensity error reductions for Earl by using TCDI/DI
Case Study: 12L (2011) Katia
CNTL
TCDI/DI
NHC Best Track in black
COAMPS-TC in color
TCDI/DI does not over-intensify Katia as much as CNTL earlier,
and gets rapid deepening better
Track Error: Homogenous Large Sample
Years: 2010-2011
Atlantic Storms: Danielle, Earl, Igor, Irene, Katia, Maria, Rina, Julia
Western North Pacific storms: Chaba, Fanapi, Ma-On
Cases: 120
ALL cases
Initial intensity < 990 hPa
TCDI/DI (blue curve) has lower track error for ALL cases and < 990 hPa
Intensity Error: Homogenous Large Sample
Years: 2010-2011
Atlantic Storms: Danielle, Earl, Igor, Irene, Katia, Maria, Rina, Julia
Western North Pacific storms: Chaba, Fanapi, Ma-On
Cases: 120
ALL cases
Initial intensity < 990 hPa
TCDI/DI (blue curve) has lowest intensity error for ALL cases and
< 990 hPa cases with more statistical significance, and further
reduced errors
Summary
• Three different TC initialization schemes have been
developed, tested with COAMPS-TC
– TCDI: tropical cyclone vortex spun-up
– DI: Full 3D dynamic initialization to analyses winds
– TCDI/DI: Run TCDI, then run DI
• TCDI/DI is shown to have superior performance
– Average intensity errors reduced by 3-5 hPa and 2-3 kts
over all lead times
– Average track errors reduced by 10-30 nm
– Better for intense initializations (< 990 hPa)
• The dynamic initialization procedures allow model
physics spin-up and “less shock”
• Future work
– DI to satellite observed heating profiles