By: Michelle TysonBy: Michelle Tyson

Department of Marine and Environmental Department of Marine and Environmental SystemsSystems

College of EngineeringCollege of EngineeringFlorida Institute of TechnologyFlorida Institute of Technology

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Source: University of South Florida

OVERVIEWOVERVIEW

Research ObjectiveResearch Objective What is ocean heat content (OHC)?What is ocean heat content (OHC)? Why is it important?Why is it important?

MethodsMethods Observed OHC vs. RTOFS OHC forecastObserved OHC vs. RTOFS OHC forecast Tropical Storm Barry (2007)Tropical Storm Barry (2007)

Compare to Hurricane Katrina (2005)Compare to Hurricane Katrina (2005) ConclusionsConclusions Questions/CommentsQuestions/Comments

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Ocean Heat Content ObjectiveOcean Heat Content Objective

study the OHC and hurricane heat potential in study the OHC and hurricane heat potential in thethe

Gulf Stream and surrounding areasGulf Stream and surrounding areas Purpose of Study:Purpose of Study:

Measure the heat content in the upper layer of the Measure the heat content in the upper layer of the

ocean between June 2, 2007 and June 8, 2007ocean between June 2, 2007 and June 8, 2007 Compare observed to the estimated forecast from Compare observed to the estimated forecast from

the Real Time Ocean Forecast System the Real Time Ocean Forecast System (RTOFS) (RTOFS)

produced by NOAA/NCEPproduced by NOAA/NCEP Will provide an evaluation of the quality of the Will provide an evaluation of the quality of the

RTOFS RTOFS hurricane heat potential forecasthurricane heat potential forecast

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What is OHC?What is OHC? Ocean heat content: The amount of heat stored in the Ocean heat content: The amount of heat stored in the

upper layers upper layers of the ocean water column. of the ocean water column. OHC plays a very important role in the formation and OHC plays a very important role in the formation and

intensity of intensity of tropical cyclones which was found during tropical cyclones which was found during research conducted research conducted on hurricanes Opal (1995) and Bret on hurricanes Opal (1995) and Bret (1999)(1999)

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Who Cares?Who Cares?

OHC plays a very OHC plays a very important role in the important role in the formation and intensity of formation and intensity of tropical cyclonestropical cyclones

Models are a useful tool in Models are a useful tool in early forecasting of early forecasting of hurricane intensity and hurricane intensity and pathpath Quality forecast models is Quality forecast models is

needed due to the needed due to the importance of early warnings importance of early warnings and forecasts of hurricanesand forecasts of hurricanes Source: Howstuffworks.com

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MethodsMethods Real-time ocean temperatures were Real-time ocean temperatures were

observed by using a observed by using a conductivity-conductivity- temperature-depth temperature-depth (CTD) profiler(CTD) profiler

The forecasted ocean temperatures The forecasted ocean temperatures were were taken from downloaded taken from downloaded archived archived RTOFS filesRTOFS files

The ocean temperatures and The ocean temperatures and salinities salinities were used to calculate were used to calculate OHC through OHC through the following the following equation:equation:

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Observed OHC vs. RTOFS OHC Forecast Observed OHC vs. RTOFS OHC Forecast for June 8, 2007for June 8, 2007

Observed Temperature vs. Depth at the 26 degree isotherm for June 8,2007

26

26.5

27

27.5

28

28.5

29

0

0.5

5

0.9

3

1.3

5

2

2.6

3

3.3

5

3.8

2

4.4

5.0

5

5.8

5

6.4

5

6.9

4

7.3

8

7.7

8

8.0

9

8.8

1

Depth (m)

Tem

pera

ture

(C

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5-Day RTOFS Temperature vs. Depth Forecast at 26 degree isotherm on June 8,2007

26

26.5

27

27.5

28

28.5

29

29.5

0 3 6 10

Depth (m)

Te

mp

era

ture

(C

)

26º C isotherm26º C isotherm

Estimated Area under curve:Estimated Area under curve:OHC: 1.64 kJ/cm²OHC: 1.64 kJ/cm²

These calculations

are under-estimatedbecause the depth of the 26° C isotherm was never reached, so therefore theocean heat content wasn’t fully calculated

Observed OHC vs. RTOFS OHC Observed OHC vs. RTOFS OHC Forecast for 2007 CruisesForecast for 2007 Cruises

Estimated Ocean Heat Content for 2007 Cruises

0.0001.0002.0003.0004.0005.0006.0007.0008.000

06/0

3/0

7

1330

1430

1515

1800

1900

2115

06/0

4/0

7

1600

06/0

5/0

7

1900

2200

06/0

6/0

7

1530

1800

2115

06/0

7/0

7

1615

1830

1915

2115

2215

2300

06/0

8/0

7

0200

Dates and Times (Z)

Ocean

Heat

Co

nte

nt

(kJ/c

m^

2)

Note: Observed OHC is indicated by the blue bars, the RTOFS 1-day Note: Observed OHC is indicated by the blue bars, the RTOFS 1-day forecast is indicated by the red bar, and the RTOFS 5-day forecastforecast is indicated by the red bar, and the RTOFS 5-day forecastis indicated by the yellow baris indicated by the yellow bar

Cooler Shelf WatersCooler Shelf WatersGulf Stream and Gulf Stream and Surrounding areasSurrounding areas

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Tropical Storm BarryTropical Storm Barry Formed in the Gulf of Formed in the Gulf of

Mexico on June 1, 2007Mexico on June 1, 2007 Winds ranging above 39 Winds ranging above 39

m.p.h.m.p.h. Moving NE toward Tampa, Moving NE toward Tampa,

FL (indicated by )FL (indicated by )

Landed on Florida’s Landed on Florida’s western coast on June 2, western coast on June 2, 2007 as a 2007 as a minimal tropical storm with minimal tropical storm with a max wind speed of 60 a max wind speed of 60 m.p.h.m.p.h.

Barely strengthened dueBarely strengthened due to high wind sheer and lowto high wind sheer and low values of OHC through thevalues of OHC through the Gulf of MexicoGulf of Mexico

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Winds increased from 65kts to 100kts (cat 3)Winds increased from 65kts to 100kts (cat 3)

August 27, 2005August 27, 2005(1200 UTC)(1200 UTC)

Hurricane KatrinaHurricane Katrina Formed in the SE of the Formed in the SE of the Bahamas on Aug. 18Bahamas on Aug. 18

Moved across southern FLMoved across southern FL 66thth strongest ever recorded strongest ever recorded 33rdrd strongest to make strongest to make

landfall in the USlandfall in the US Over 1800 lives takenOver 1800 lives taken

24.5º N24.5º N84.5º W84.5º W

Increased to a cat 5 with peak winds of 150 ktsIncreased to a cat 5 with peak winds of 150 kts

August 28, 2005August 28, 2005(1800 UTC)(1800 UTC)

26.5º N26.5º N89.5º W89.5º W

A low ocean heat content was A low ocean heat content was calculated calculated for observed and RTOFSfor observed and RTOFS

A small difference of OHC in notedA small difference of OHC in noted Warmer waters of the Gulf Stream vs. Warmer waters of the Gulf Stream vs.

cooler cooler shelf shelf waterswaters

RTOFS 1-day model forecasted OHC RTOFS 1-day model forecasted OHC values higher than the observed values higher than the observed

The difference was very minimal~ The difference was very minimal~ 0.448 0.448 kJ/cm²kJ/cm²

ConclusionsConclusions

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Conclusions Cont’dConclusions Cont’d RTOFS 5-day model forecasted OHC values RTOFS 5-day model forecasted OHC values

lower than lower than the observed on June 3the observed on June 3rdrd,4,4thth,6,6thth, , 77thth

RTOFS forecasted values of 0 kJ/cm² due to RTOFS forecasted values of 0 kJ/cm² due to temperatures lower than 26º Ctemperatures lower than 26º C

RTOFS 5-day model forecasted OHC values RTOFS 5-day model forecasted OHC values higher higher than the observed on June 5than the observed on June 5thth and 8 and 8thth

Average difference was .523 kJ/cm²Average difference was .523 kJ/cm²

OHC shown to change the strength of tropical OHC shown to change the strength of tropical stormsstorms High OHC strengthened Katrina (2005)High OHC strengthened Katrina (2005) Low OHC stalled strengthening of Barry (2007)Low OHC stalled strengthening of Barry (2007)

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QUESTIONS??QUESTIONS??