JHT Project: Evaluation and Improvement of Ocean Model Parameterizations for NCEP Operations (Ivan)

L. K. Shay, G. Halliwell, J.Brewster, C. Lozano, W. TeagueMPO, RSMAS, Univ. of Miami

EMC-NCEPOceanography Department, NRL-Stennishttp://isotherm.rsmas.miami.edu/~nick

JHT Project Objectives:

Ivan an example of negative feedback (cold wake cooling and Cold Core Ring) as opposed to less negative feedback (Loop Current/Warm Core Rings)

By building on a previous JHT, specific objectives are: • optimizing spatial resolution that will permit the ocean model to

run efficiently as possible without degrading the simulated response;

• improving the initial background state provided to the ocean model;

• improving the representation of vertical and horizontal friction and mixing;

• generating realistic high-resolution atmospheric forcing fields necessary to achieve these objectives; and

• Testing differing formulations of the drag coefficient (cd).

MOTIVATION:

Ivan (2004) over the GOM SSH (cm) from HYCOM (from Halliwell et al., MWR, 2008).

SST Analyses

Northern Cyclone

Southern Cyclone

Ivan’s Track and Intensity Relative to OHC (left) NRL SEED Mooring Locations in Northern Gulf of Mexico Relative

to Bottom Depth (Right) (Teague et al., JPO, 2007).

14 ADCP moorings- Focus here in Array 9.

HYbrid Coordinate Ocean Model (HYCOM)Hurricane Ivan Simulations 10 Sept-6 Oct 04

Configuration:• 0.04° Mercator grid, Gulf of Mexico domain• No data assimilation performed

Initial and boundary conditions from U.S. Navy HYCOM ocean nowcast-forecast system:•Data assimilative ocean nowcast•Navy Coupled Ocean Data Assimilation (NCODA) assimilation

Atmospheric Forcing:•Navy 27 km COAMPS atmospheric model•Vector wind blended with higher resolution fields from HWIND •Wind stress for HWIND calculated using Donelan cd

Hurricane Ivan Modeling Experiment Summary

Model Attribute Baseline Experiment GOM1 Alternate Experiments

Horizontal resolution 0.04° Mercator GOM2: 0.08° Mercator

Vertical resolution 26 layers, 4-8m in OML GOM3: 21 layers, 7.5-15m in OMLGOM4: 31 layers, 3-5m in OML

Vertical mixing KPP GOM5: MYGOM6: GISS

CD Donelan GOM7: PowellGOM8: Large and PondGOM9: Large and Pond (capped)GOM10: Shay and Jacob

CEL, CES COARE3.0 algorithm GOM11: Kara et al.

Atmospheric forcing 27-km COAMPS+H*WIND GOM12: 27-km COAMPS only

Outer model NCODA GoM hindcast GOM13: Free GOM simulation

Ocean Dynamics 3-D Ocean Physics GOM14:1-D Column Models

Intense Forcing (upper) and

Relaxation Stages (lower) for NRL SEED moorings 7-14

7-10 Red ~500 m

11-14 Yellow~1000 m

(Teague et al. JPO, 2007).

M9 (1.5 Rmax) Observed and Near-Inertial Current Shear Response (Rmax= 32 km)

Normalized shear by 10-2 s-1 based on Isidore/Lili

RMS SST (oC) Differences

Pre Ivan SST

Post-Ivan SST

Pre-Post Ivan ΔSST

TMI and KPP SST Comparisons

Observed/Simulated Current Response at M9 (1.5 Rmax)from 7 ExperimentsHalliwell et al., MWR, (2009)

Below cd using ocean response as a tracer in Shay and Jacob (2006)

Current Time Series Comparisons @ 1.5 Rmax

U (east-west) V (north-south)

Taylor Diag., simulations vs. baseline:

SST;

v Current at M9 (1.5Rmax).

(Halliwell et al., MWR, 2009)

Taylor Diag., simulations vs. observations:

SST;

v Current at M9 (1.5Rmax).

(Halliwell et al., MWR, 2009)

Progress Summary and Blueprint For Future

Ivan a clear example of negative feedback (wake cooling/mixing induced by strong winds and Cold Core Ring) as opposed to positive feedback over the Loop Current and Warm Core Rings.

SST modulated by warm and cold ocean features that have to be properly initialized in ocean models and mixing. Data assimilation schemes are essential!

Trifecta Katrina, Rita and Wilma is next.

Temperatures and currents needed to assess mixing schemes and evaluate initialization schemes. Both Eulerian (AXCP, AXCTD, moorings) and Lagrangian (drifters, floats) needed – Targeted Obs in storm coordinates!

Working with MMS on 5-year Loop Current Dynamical Study, NOAA HFIP and NSF.

Sampling Pattern: AXCTDs and Drifters relative to OHC and Rita’s track.

Pre (15 Sep) and Post Rita (26 Sep) WCR/CCR/ LC OHC and 26oC isotherm depth.

Vertical structure from AXCTDs

(Jaimes and Shay, MWR, 2009a)