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, USA2University 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 ConferencesMontreal, 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/DIApplication to TC Prediction Using COAMPS-TC

NOGAPS/NCEP analysis

3DVAR data assimilation Remove TC vortex

Generate vortex from TCDI

(nudge MSLP)Insert vortex

Run forecast model

Warm Start

Cold Start

12-h forward DI

CNTL

DITCDI

TCDI

TCDI

TCDI

/DI

CNTL: Standard 3DVAR Initialization

DI: 3D Dynamic Initialization to analysis momentum ua (12-h relaxation) after 3DVAR

TCDI: Tropical Cyclone Dynamic Initialization (TC component is dynamic) after 3DVAR

TCDI/DI: Run TCDI, then run DI

)

Synthetic TC obs, Liou and Sashegy (2011)

TCDI: Hendricks et al. (2011) WAF, Zhang et al. (2012) WAF

COAMPS-TC OverviewCurrent and Future Capabilities

• 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)

• 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

• 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

• 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)

Ocean Analysis

Ocean ModelsAtmospheric Model

Atmospheric Analysis

Atmospheric Ensembles• Initial Cond. Perturbation: ET, EnKF• Physics Perturbations: PBL, Convection…• Lateral BCs: Global ensemble (NOGAPS)• Probabilistic Products: Intensity, track…

Ocean Ensembles• 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 schemeInitialization/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)

• During DI, the winds are held quasi-constant• 3DVAR is not able to produce gradient balanced

vortex, rapid adjustment to winds during DI

10-m Winds (kt) Sea Level Pressure (hPa)

CNTL TCDI

TCDI/DIDI

2011 IRENE(09L)

Wind Structure Verification (t=0 h)

H*WIND

Hurricane Irene (09L), 2011082512

COAMPS-TC using CNTL

COAMPS-TC using TCDI/DI

H*WIND courtesy NOAA/AOML/HRD Powell et. al (2010)

COAMPS-TC using DI

10-m Winds (kt)

Case Study: 08W (2011) Ma-On

Significant intensity error reductions for Ma-On by using TCDI/DI

15 cases

10 kt

CNTL TCDI/DIJTWC Best Track in blackCOAMPS-TC in color

Case Study: 07L (2010) Earl

CNTL TCDI/DI

Significant intensity error reductions for Earl by using TCDI/DI

13 cases10 hPa

NHC Best Track in blackCOAMPS-TC in color

Case Study: 12L (2011) KatiaTCDI/DICNTL

TCDI/DI does not over-intensify Katia as much as CNTL earlier, and gets rapid deepening better

NHC Best Track in blackCOAMPS-TC in color

Track Error: Homogenous Large Sample

TCDI/DI (blue curve) has lower track error for ALL cases and < 990 hPa

ALL cases Initial intensity < 990 hPa

Years: 2010-2011Atlantic Storms: Danielle, Earl, Igor, Irene, Katia, Maria, Rina, Julia

Western North Pacific storms: Chaba, Fanapi, Ma-OnCases: 120

Intensity Error: Homogenous Large Sample

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

Years: 2010-2011Atlantic Storms: Danielle, Earl, Igor, Irene, Katia, Maria, Rina, Julia

Western North Pacific storms: Chaba, Fanapi, Ma-OnCases: 120

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