Assimilating and determining the Assimilating and determining the impact of sea surface winds impact of sea surface winds

measured by WindSat/Coriolis data measured by WindSat/Coriolis data in the Global Forecast Systemin the Global Forecast System

Li Bi

Tom Zapotocny

James Jung

Michael Morgan

31 May 2006

OverviewOverview

WindSat is a WindSat is a polarimetric polarimetric microwave radiometermicrowave radiometer

Measures ocean Measures ocean surface wind speed surface wind speed and directionand direction

Launched on 6 Launched on 6 January 2003January 2003

WindSat on Coriolis satellite

WindSat OrbitWindSat Orbit Sun-synchronous Sun-synchronous

circular orbitcircular orbit 830 km altitude830 km altitude 98.7 degrees of inclination98.7 degrees of inclination 1800 Local Time of the 1800 Local Time of the

Ascending Node (LTAN)Ascending Node (LTAN) about 14.1 orbits per dayabout 14.1 orbits per day

1800 LTAN for 1800 LTAN for validation with validation with QuikSCATQuikSCAT

WindSat instrument WindSat instrument has 1025 km swath has 1025 km swath widthwidth

http://www.seaspace.com/news

http://www.seaspace.com/news

Projected CapabilitiesProjected Capabilities

Demonstrate the capability of Demonstrate the capability of polarimetric microwave radiometry to polarimetric microwave radiometry to measure the ocean surface wind vector measure the ocean surface wind vector from space.from space.

How ocean surface physics change with How ocean surface physics change with wind and boundary layer conditions.wind and boundary layer conditions.

WindSat will aid with forecast of short-WindSat will aid with forecast of short-term weather, issuing timely weather term weather, issuing timely weather warnings and gathering general climate warnings and gathering general climate data.data.

How WindSat can measure How WindSat can measure wind speed and direction?wind speed and direction?

Wind roughening the surface of the Wind roughening the surface of the ocean causes an increase in the ocean causes an increase in the brightness temperature of the brightness temperature of the microwave radiation emitted from the microwave radiation emitted from the water’s surface.water’s surface.

Multiple Multiple frequencies and polarizations allow for simultaneous retrievals of different surface and atmospheric parameters.

Ocean Brightness Ocean Brightness TemperaturesTemperatures

Tb’s measured by Tb’s measured by satellite radiometer satellite radiometer consists of:consists of: Signal that is emitted Signal that is emitted

from the ocean from the ocean surface and travels surface and travels upwardsupwards

Upward traveling Upward traveling atmospheric radiationatmospheric radiation

Downward traveling Downward traveling atmospheric and cold atmospheric and cold space radiation that is space radiation that is scattered back from scattered back from the ocean surfacethe ocean surface

http://www.ofcm.gov

Principles of OperationPrinciples of Operation

WindSat measures full polarizations. WindSat measures full polarizations.

rclc

h

v

TT

TT

T

T

V

U

Q

I

Is4545

Band, GHz Polarizations Horizontal Spatial Resolution, km

6.8 V, H 40 x 60

10.7 V, H, +45, -45, L, R

25 x 38

18.7 V, H, +45, -45, L, R

16 x 27

23.8 V, H 12 x 20

37.0 V, H, +45, -45, L, R

8 x 13

CLW Retrievals

18.7,28.8 and 37GHz

WV Retrievals

18.7,23.8 and 37GHz

Wind Speed Retrievals

10.7,18.7,23.8 and 37GHz

SST Retrievals

10.7GHz

Wind Direction Retrievals

10.7, 18.7 and 37GHz3rd and 4th Stokes

biclwi TaL

biwvi Tav

biui Tau

bisstisst TaT

5

1 ,

2mod,,

)(

))((

imeasViU

VUmeasViU

TVar

TTJ

NOAA WindSat Wind NOAA WindSat Wind Vector Retrieval Vector Retrieval Algorithm – Ver 0Algorithm – Ver 0

http://cioss.coas.oregonstate.edu/

Sample picture of WindSat wind speed from a Sample picture of WindSat wind speed from a preliminary wind vector retrieval algorithm.preliminary wind vector retrieval algorithm.

http://manati.orbit.nesdis.noaa.gov/cgi-bin/ws_wdsp_day_noaa.pl

Proposed workProposed work Work with the JCSDA (Joint Center for Work with the JCSDA (Joint Center for

Satellite Data Assimilation) to evaluate the Satellite Data Assimilation) to evaluate the impact of assimilating WindSat data in the impact of assimilating WindSat data in the NCEP GFS (Global Forecast System) model. NCEP GFS (Global Forecast System) model. A November 2005 version of the SSI and GFS A November 2005 version of the SSI and GFS were used and run at T254L64.were used and run at T254L64.

Compare the forecast impact with QuikSCAT Compare the forecast impact with QuikSCAT data from the same time period. QuikSCAT data from the same time period. QuikSCAT data have provided a positive impact on data have provided a positive impact on forecastsforecasts

Data time period: 1 Jan – 15 Feb 2004Data time period: 1 Jan – 15 Feb 2004

First Goal First Goal

Run GFS with QuikSCAT (cntrl254)Run GFS with QuikSCAT (cntrl254)

Run GFS without QuikSCAT (noqscat254)Run GFS without QuikSCAT (noqscat254)

Study forecast impact for QuikSCAT windsStudy forecast impact for QuikSCAT winds

22 2

1 1 1( )( ) ( ) /{( ) }

NN N

i ii i i ii i i

C AD A C AFI 100

N N N

Error in experimentError in controlError in control

0.4

0.5

0.6

0.7

0.8

0.9

1

6-Jan 11-Jan 16-Jan 21-Jan 26-Jan 31-Jan 5-Feb 10-Feb 15-Feb

cntrl254 0.8413

noqscat254 0.8409

0.4

0.5

0.6

0.7

0.8

0.9

1

6-Jan 11-Jan 16-Jan 21-Jan 26-Jan 31-Jan 5-Feb 10-Feb 15-Feb

cntrl254 0.7833

noqscat254 0.7740

The 500 hPa geopotential height anomaly correlation at day 5 for 20-80N (7 Jan–15 Feb 2004)

The 500 hPa geopotential height anomaly correlation at day 5 for 20-80S (7 Jan–15 Feb 2004)

N. Hemisphere 500 hPa AC Z 20N - 80N Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

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0.75

0.8

0.85

0.9

0.95

1

0 1 2 3 4 5 6 7

Forecast [days]

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Control Noqscat

S. Hemisphere 500 hPa AC Z 20S - 80S Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

0 1 2 3 4 5 6 7

Forecast [day]

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Control Noqscat

Second Goal Second Goal Run GFS with WindSat (windsob1°254)Run GFS with WindSat (windsob1°254)

Run GFS with WindSat (windsob0.5°254)Run GFS with WindSat (windsob0.5°254)

Run GFS with WindSat no QuikSCAT (windnoq254)Run GFS with WindSat no QuikSCAT (windnoq254)

Compare forecast impact for WindSat winds with Compare forecast impact for WindSat winds with the forecast impact for QuikSCAT windsthe forecast impact for QuikSCAT winds

Develop and improve QC techniques and verify the Develop and improve QC techniques and verify the current retrieval algorithmcurrent retrieval algorithm

Additional WindSat Quality Additional WindSat Quality ControlControl

Data used only at 6 hour synoptic time Data used only at 6 hour synoptic time with a plus/minus 3 hour windowwith a plus/minus 3 hour window..

If the absolute value of the observed wind If the absolute value of the observed wind component is more than 6 mscomponent is more than 6 ms-1 -1 from the from the corresponding background wind corresponding background wind component the observation is eliminated. component the observation is eliminated. This only removed the extreme outliers. This only removed the extreme outliers.

Control ----- T254L64 to 7 days (no AMSU, no AQUA AIRS, no QuikSCAT)NoQuikSCAT ----- T254L64 to 7 days (no AMSU, no AQUA AIRS, with QuikSCAT)WindSat 1.0 ----- T254L64 to 7 days (control + WindSat QC check and superobing to 1 deg)WindSat 0.5 ----- T254L64 to 7 days (control + WindSat QC check and superobing to 0.5 deg)

WindSat Assimilation Statistics

0.7

0.72

0.74

0.76

0.78

0.8

0.82

0.84

0.86

nh1000 nh 500 sh 1000 sh 500

Control NoQuikSCAT 0.5 Windsat 1.0 Windsat 0.5

0.4

0.5

0.6

0.7

0.8

0.9

1

6-Jan 11-Jan 16-Jan 21-Jan 26-Jan 31-Jan 5-Feb 10-Feb 15-Feb

cntrl254 0.8413noqscat254 0.8409wind_sob_1.0deg 0.8393wind_sob_0.5deg 0.8365

0.4

0.5

0.6

0.7

0.8

0.9

1

6-Jan 11-Jan 16-Jan 21-Jan 26-Jan 31-Jan 5-Feb 10-Feb 15-Feb

cntrl254 0.7833noqscat254 0.7740wind_sob_1.0deg 0.7811wind_sob_0.5deg 0.7724

The 500 hPa geopotential height anomaly correlation at day 5 for 20-80N (7 Jan–15 Feb 2004)

The 500 hPa geopotential height anomaly correlation at day 5 for 20-80S (7 Jan–15 Feb 2004)

1000 hPa magnitude of wind difference 2004011806 (Control – WindSat)

SLP difference 2004011806 (Control – WindSat)

N. Hemisphere 500 hPa AC Z 20N - 80N Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

0.7

0.75

0.8

0.85

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1

0 1 2 3 4 5 6 7

Forecast [days]

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Control Windsat

S. Hemisphere 500 hPa AC Z 20S - 80S Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

0.7

0.75

0.8

0.85

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0.95

1

0 1 2 3 4 5 6 7

Forecast [day]

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Control Windsat

S. Hemisphere 500 hPa AC Z 20S - 80S Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

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Forecast [day]

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Windsat1.0 Windsat0.5

N. Hemisphere 500 hPa AC Z 20N - 80N Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

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Windsat1.0 Windsat0.5

WindSat vs. WindSat vs. QuikSCATQuikSCAT ResolutionResolution 25km (Experimental GDAS)25km (Experimental GDAS)

EDR’s (environmental data EDR’s (environmental data recordsrecords ) ) TPW TPW CLW CLW Rain Rate Rain Rate SST SST Wind SpeedWind Speed

std~0.8m/s [3-20]m/sstd~0.8m/s [3-20]m/s Wind DirectionWind Direction

Std~25Std~25° for wspd<6m/s° for wspd<6m/s Sdt~17° for wspd >6m/sSdt~17° for wspd >6m/s

LimitationLimitation CLW>0.2mm degradation in CLW>0.2mm degradation in

retrievals of surface retrievals of surface parametersparameters

ResolutionResolution 25km (Operational 25km (Operational

GDAS)GDAS) 12.5km12.5km 2.5km2.5km

EDR’s EDR’s

Wind SpeedWind Speed Std ~0.8m/s [3-35]m/sStd ~0.8m/s [3-35]m/s

Wind DirectionWind Direction Std Std ≤≤ 20 20° for wspd>3m/s° for wspd>3m/s

LimitationLimitation Wind speed and direction Wind speed and direction

retrievals degrade in retrievals degrade in rainy areasrainy areas

http://www.ofcm.gov

WindSat and QuikSCAT Wind WindSat and QuikSCAT Wind FieldsFields

WindSat QuikSCAT

http://www.npoess.noaa.gov/polarmax

N. Hemisphere 500 hPa AC Z 20N - 80N Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

0.7

0.75

0.8

0.85

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0.95

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Forecast [days]

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Noqscat Windsat

S. Hemisphere 500 hPa AC Z 20S - 80S Waves 1-20

1 Jan - 15 Feb '04

0.6

0.65

0.7

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Noqscat Windsat

WindSat (1° superob) and QuikSCAT (0.5° superob)WindSat (1° superob) and QuikSCAT (0.5° superob) data counts and RMS error (20040125) data counts and RMS error (20040125)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

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1

6-Jan 11-Jan 16-Jan 21-Jan 26-Jan 31-Jan 5-Feb 10-Feb 15-Feb

cntrl 0.7111

wind1.0_deg sob 0.7095

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

6-Jan 11-Jan 16-Jan 21-Jan 26-Jan 31-Jan 5-Feb 10-Feb 15-Feb

cntrl 0.5312

wind1.0_deg sob 0.5265

The 1000 hPa wind speed anomaly correlation at day 5 for 20-80N (7 Jan–15 Feb 2004)

The 1000 hPa wind speed anomaly correlation at day 5 for 20-80S (7 Jan–15 Feb 2004)

Geopotential height anomaly correlation of Wind_sob_1.0deg and QuikSCAT_0.5deg at day 5 for 20-80N and 20-80S (7

Jan–15 Feb 2004)

0

100

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1000

0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95

NH_WindSatSH_WindSatNH_QuikSCATSH_QuikSCAT

Future GoalsFuture Goals Examine the direct assimilation of the Examine the direct assimilation of the

WindSat radiances into the GFS by either WindSat radiances into the GFS by either updating the spectral statistical updating the spectral statistical interpolation (SSI) assimilation system or interpolation (SSI) assimilation system or switching to the GSI. switching to the GSI.

Conduct the same study with higher Conduct the same study with higher operational resolution (T382) and an operational resolution (T382) and an alternate season. alternate season.

Study the regional impact of WindSat Study the regional impact of WindSat assimilation and compare the difference assimilation and compare the difference between WindSat and QuikSCAT data. between WindSat and QuikSCAT data.

ConclusionsConclusions Preliminary results indicate that QuikSCAT Preliminary results indicate that QuikSCAT

data improved the forecast more than WindSat data improved the forecast more than WindSat data for a majority of the cases examined.data for a majority of the cases examined.

The combination of WindSat and QuikSCAT The combination of WindSat and QuikSCAT provided the largest positive forecast impact provided the largest positive forecast impact by day 7.by day 7.

At T254 WindSat demonstrated larger AC At T254 WindSat demonstrated larger AC gains with a 1° superob than a 0.5° superob. gains with a 1° superob than a 0.5° superob. (QuikSCAT uses a 0.5° superob by default).(QuikSCAT uses a 0.5° superob by default).

AcknowledgementsAcknowledgements

• Prof. Michael Morgan (UW-AOS) for Prof. Michael Morgan (UW-AOS) for giving insightful advice and for local giving insightful advice and for local computer resources.computer resources.

• Stephen Lord (NCEP) for computer Stephen Lord (NCEP) for computer resources and tape space.resources and tape space.

• Stacie Bender and Dennis Keyser for Stacie Bender and Dennis Keyser for collecting and processing our various collecting and processing our various data streams.data streams.