Ocean Initialization Ocean Initialization System for Coupled System for Coupled

Hurricane-Ocean Models Hurricane-Ocean Models and its Transition to and its Transition to

HWRFHWRF

Isaac GinisIsaac Ginisandand

Richard YablonskyRichard Yablonsky

University of Rhode IslandUniversity of Rhode Island

6161stst Interdepartmental Hurricane Interdepartmental Hurricane ConferenceConference

6 March, 20076 March, 2007

Why Proper Ocean Initialization in a Coupled Why Proper Ocean Initialization in a Coupled Hurricane-Ocean Model is Needed for Accurate Hurricane-Ocean Model is Needed for Accurate

Hurricane Forecasting? Hurricane Forecasting?

• Wind-induced mixing of the upper ocean generates the Wind-induced mixing of the upper ocean generates the cold wake by entraining cooler water from belowcold wake by entraining cooler water from below

• The entrainment rate is greatly dependent on the depth of The entrainment rate is greatly dependent on the depth of the upper ocean warm layer.the upper ocean warm layer.

Ocean Model Initialization ChallengeOcean Model Initialization Challenge

Accurate representation of mesoscale oceanic features Accurate representation of mesoscale oceanic features is needed, such as the penetration of the Loop is needed, such as the penetration of the Loop Current into the Gulf of Mexico and the shedding of Current into the Gulf of Mexico and the shedding of Loop Current eddies.Loop Current eddies.

Depth of 26oC isotherm on September 15, 2005(courtesy of Michelle Mainelli, TPC)

Ocean Initialization Methods that can be Utilized Ocean Initialization Methods that can be Utilized in a Hurricane-Ocean Coupled Modelin a Hurricane-Ocean Coupled Model

• A continuously run ocean model with A continuously run ocean model with assimilation of assimilation of in situin situ and/or remotely- and/or remotely-sensed observationssensed observations that is capable of that is capable of predicting the position of the LC and LCEs. predicting the position of the LC and LCEs.

• A feature-based modeling procedure that is A feature-based modeling procedure that is capable to adjust the background LC capable to adjust the background LC position and structure and directly insert position and structure and directly insert LCEs with real-time LCEs with real-time in situin situ and/or and/or remotely-sensed observations. remotely-sensed observations.

Feature-Based Initialization ProcedureFeature-Based Initialization Procedure

• This procedure is based on a feature This procedure is based on a feature modeling approach that allows a realistic modeling approach that allows a realistic simulation of the cross-frontal temperature, simulation of the cross-frontal temperature, salinity and velocity of oceanic fronts and salinity and velocity of oceanic fronts and eddies. eddies.

• We developed an innovative method of We developed an innovative method of cross-frontal “sharpening” of the cross-frontal “sharpening” of the background temperature and salinity fields, background temperature and salinity fields, which is guided by observed cross-sections which is guided by observed cross-sections obtained in specialized field experiments. obtained in specialized field experiments.

Identifying LC and LCEs in the Gulf of Identifying LC and LCEs in the Gulf of Mexico from Sea Surface HeightMexico from Sea Surface Height

• During the winter months, the LC and LCE positions are During the winter months, the LC and LCE positions are often identifiable from the SST field, however during the often identifiable from the SST field, however during the hurricane season the SST is nearly homogeneous in the hurricane season the SST is nearly homogeneous in the Gulf.Gulf.

• The LC and LCEs can be identified by the difference in the The LC and LCEs can be identified by the difference in the sea surface height. The daily sea-surface height anomaly sea surface height. The daily sea-surface height anomaly (SHA) is produced at Stennis Space Center in Mississippi (SHA) is produced at Stennis Space Center in Mississippi by blending multiple ground tracks from satellites. by blending multiple ground tracks from satellites.

• The altimetric SHA is used daily by the Tropical Prediction The altimetric SHA is used daily by the Tropical Prediction Center to calculate the depth of the 26Center to calculate the depth of the 26°C isotherm and °C isotherm and integrate it into the Statistical Hurricane Intensity Prediction integrate it into the Statistical Hurricane Intensity Prediction Scheme (SHIPS) Scheme (SHIPS)

Daily NCEPDaily NCEPSSTSSTAnalysisAnalysis

SST GDEM SST GDEM SeptemberSeptemberclimatologyclimatology

SHA from SHA from satellitesatellitealtimetryaltimetry

Depth of 26C Depth of 26C isotherm isotherm derived at TPCderived at TPC

Identifying LC and LCEs in the Gulf of Identifying LC and LCEs in the Gulf of Mexico from Sea Surface HeightMexico from Sea Surface Height

September 15, 2005September 15, 2005

AXBT MeasurementsAXBT Measurements

AXBTs provide accurate measurements of the ocean temperature AXBTs provide accurate measurements of the ocean temperature to a depth of ~300-400 m. Temperature profiles for this study were to a depth of ~300-400 m. Temperature profiles for this study were provided by provided by E. Uhlhorn at HRD.E. Uhlhorn at HRD.

In advance of hurricane Rita, on 15 September 2005, HRD scientists deployed AXBTsIn advance of hurricane Rita, on 15 September 2005, HRD scientists deployed AXBTs

Results of Feature-Based Model Results of Feature-Based Model Initialization on Sep. 15, 2005Initialization on Sep. 15, 2005

ModelModel TPC Analysis TPC Analysis

Depth of 26oC isotherm

Evaluation of the Feature-based Initialization Evaluation of the Feature-based Initialization Scheme and Comparison with RSMAS Scheme and Comparison with RSMAS

HYCOM Prediction SystemHYCOM Prediction System

• Evaluation is done by comparing the model and Evaluation is done by comparing the model and observed temperature profiles at each AXBT observed temperature profiles at each AXBT location.location.

• RSMAS HYCOM dataset from 15 September 2005 RSMAS HYCOM dataset from 15 September 2005 was downloaded from the HYCOM consortium was downloaded from the HYCOM consortium data server website. RSMAS HYCOM assimilates data server website. RSMAS HYCOM assimilates SST and satellite altimetry.SST and satellite altimetry.

1

2

3

457 6

75-m Temp. (SSH/SST-assimilated) with AXBT locations

8

9

10

1113 12

75-m Temp. (SSH/SST-assimilated) with AXBT locations

14

15

16

1718

75-m Temp. (SSH/SST-assimilated) with AXBT locations

Ocean Heat ContentOcean Heat Content

OHC provides a OHC provides a quantitative measure quantitative measure of the heat energy of the heat energy available to an available to an approaching tropical approaching tropical cyclone cyclone

Feature-basedFeature-basedinitializationinitialization

RSMAS RSMAS HYCOMHYCOM

OHC is the integrated heat content from the ocean’s surface to 26OHC is the integrated heat content from the ocean’s surface to 26ooCC

Evaluation of OHC at AXBT LocationsEvaluation of OHC at AXBT Locations

TCHP rmse: TCHP rmse:

Feature-based: Feature-based: 9.5 kJ cm9.5 kJ cm-2-2

RSMAS HYCOM: RSMAS HYCOM: 26.0 kJ cm26.0 kJ cm-2-2

Operational implementationOperational implementation

Feature-based initialization of the LC and LCEs was implemented Feature-based initialization of the LC and LCEs was implemented operationally in the GFDL coupled model in 2006.operationally in the GFDL coupled model in 2006.

Examples of LC and LCE parameters input for Examples of LC and LCE parameters input for the ocean model initialization the ocean model initialization

TABLE 1. LC parameters.TABLE 1. LC parameters.

Parameter(s)Parameter(s) DescriptionDescription

22 LC’s intrusion into GoM initialized with 2 axesLC’s intrusion into GoM initialized with 2 axes

-87.3, 27.4-87.3, 27.4 Lat/Lon position of northernmost LC intrusionLat/Lon position of northernmost LC intrusion

-86.6, 23.5-86.6, 23.5 Lat/Lon position of LC as it enters the GoMLat/Lon position of LC as it enters the GoM

-84.6, 24.6-84.6, 24.6 Lat/Lon position of LC at merge with Florida CurrentLat/Lon position of LC at merge with Florida Current

-89.5, 25.5-89.5, 25.5 Lat/Lon position of western edge of LC axis bendLat/Lon position of western edge of LC axis bend

-86.6, 25.5-86.6, 25.5 Lat/Lon position of eastern edge of LC axis bendLat/Lon position of eastern edge of LC axis bend

00 LCPROFILE is defined using GDEM Caribbean profile LCPROFILE is defined using GDEM Caribbean profile

TABLE 2. LCE parameters.TABLE 2. LCE parameters.

Parameter(s)Parameter(s) DescriptionDescription

22 Two rings are simulated in the GoMTwo rings are simulated in the GoM

11 First ring is a WCR (WCR1)First ring is a WCR (WCR1)

0.80.8 Not used in this case because using real dataNot used in this case because using real data

-93.3, 26.7-93.3, 26.7 Lat/Lon position of western edge of WCR1 major axisLat/Lon position of western edge of WCR1 major axis

-89.7, 26.7-89.7, 26.7 Lat/Lon position of eastern edge of WCR1 major axisLat/Lon position of eastern edge of WCR1 major axis

1.21.2 Radius (deg) of WCR1 minor axisRadius (deg) of WCR1 minor axis

11 WCR1PROFILE is defined using real data (see below) WCR1PROFILE is defined using real data (see below)

SummarySummary• Using a feature-based modeling approach that Using a feature-based modeling approach that

assimilates satellite-derived SSH and SST, a new assimilates satellite-derived SSH and SST, a new ocean initialization has been developed and ocean initialization has been developed and implemented operationally for the GFDL coupled implemented operationally for the GFDL coupled model in 2006. model in 2006.

• Feature-based initialization provides more Feature-based initialization provides more accurate estimates of OHC than a continuously accurate estimates of OHC than a continuously run three-dimensional ocean model (i.e. RSMAS run three-dimensional ocean model (i.e. RSMAS HYCOM) HYCOM)

• This initialization technique is being transitioned This initialization technique is being transitioned to the HWRF system for the 2007 hurricane to the HWRF system for the 2007 hurricane season.season.