High Quality Wind Retrievals for Hurricanes Using the SeaWinds Scatterometer

W. Linwood Jones and Ian AdamsCentral Florida Remote Sensing Lab

Univ. of Central FL

Presentation Outline

Hurricane Wind Vector Retrieval Issues CFRSL Hurricane Retrieval Algorithm QRad Rain Rate Algorithm Isabel and Fabian Results Conclusion

Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

Wind retrievals not tuned for high wind speeds Geophysical Model Function developed for wind

speeds < 20 m/s

CFRSL Approach Tropical Cyclone GMF tuned for retrieving high wind

speeds Blended UMASS aircraft scat measurements and

NSCAT GMF

Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

Egg spatial resolution @ 25 km sampling is too coarse

CFRSL ApproachUses gridded “slice sigma-o” @ 12.5 Km

sampling

25 km resolution using “eggs”

50 k

m

25 k

m

Longitude

Lat

itude

Range gated “slices” from “egg”

6 km

30 km

12.5 km

25 km

Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

Rain has negative effects on wind measurementsRain attenuation lowers retrieved wind speedsVolume scattering increases retrieved wind

speeds and alters directional signaturesRain “splash” increases retrieved wind speeds

and changes anisotropic ocean surface features

MUDDH performance in hurricanes is poor

Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

Rain has negative effects on wind measurements

CFRSL ApproachSimultaneous rain measurement using QRadRain attenuation and volume backscatter

correction providedRain splash effect included in GMFRain Quality Flags Provided

CFRSL Hurricane Retrieval Algorithm

“Slice” sigma-0’s for improved spatial resolution - 12.5 km

Sigma-0 minimum eye location Wind speed retrieved from individual sigma-0

(assumed spiral wind directions) Rain inferred using QRad rain rate algorithm Sigma-0 corrections from atmospheric

transmissivity and rain volume backscatter Flag pixels that correspond to high rain

attenuation

QRad Algorithm Block Diagram

Bin Slice Sig-0

SpiralWind Direction

Atmos. Attenand

BackscatterCorrection

L2A Tb’s

Hurricane Wind Speed

QScatL1B sig-0

Locate Center

QRadRain Rate

RetrieveWind Speed

Hurricane Wind Retrieval

Hurricane Eye Location

Based uponAverage of “4-flavor”Sigma-0’s12.5 kmsampling

Longitude

Lat

itude

QRad/SRad Rain Algorithm

Look at noise channel of scatterometerSubtract echo channelCalibrate radiometric temperature vs. TMI

Train brightness temperature/rain rate relationship via TMI

Coincident with scatterometer measurement

QRad Integ. Rain Rate Product

Improved CFRSL rain retrieval algorithm provides earth-gridded 50 km data product

Instantaneous integrated rain rates > 2.4 km*mm/hr

Resampled to 12.5 km wind vector grid

QRad – TRMM 2A12 Instantaneous Rain Rate

QRad TMI

Longitude

Lat

itu

de

Land

QRad – TRMM 3B42RT HQ Instantaneous Collocated Low Rain event

QRadTMI

QRad – TRMM 3B42RT HQ Instantaneous Collocated Moderate Rain event

QRadTMI

QRad – TRMM 3B42RT HQ Instantaneous Collocated High Rain Event

QRadTMI

QRad (CFRSL) & TMI Integrated Rain Rates for Simultaneous Events

TMI Integ. Rain Rate, km*mm/hr

CF

RS

L I

nteg

. Rai

n R

ate,

km

*mm

/hr

AMSR vs. SRad Path Attenuation, Horizontal Polarization

102

AMSR Attenuation SRad Attenuation

2003 Hurricane Results

HRD Wind Field, Time Interpolated CFRSL Wind Retrieval

QRad Rain Rate(mm/hr)

QuikSCAT Rev. 22055, Sept 13, 2003 22:04 Z

(m/sec)

SSMI Rain Rate

HRD Wind Field, Time Interpolated(m/sec)

SeaWinds Rev. 03927, Sept 15, 2003 15:40 Z

SRad Rain Rate(mm/hr)

CFRSL Wind Retrieval

SSMI Rain Rate

CFRSL Wind Retrieval

SRad Rain Rate(mm/hr)

HRD Wind Field, Time Interpolated(m/sec)

QuikSCAT Rev. 22084, Sept 15, 2003 22:52 Z

SSMI Rain Rate

HRD Wind Field 01:30 Z

SeaWinds Rev. 03934, Sept 16, 2003 02:52 Z

CFRSL Wind Retrieval

SRad Rain Rate(mm/hr)

(m/sec)

SSMI Rain Rate

HRD Modeled Wind Speed (m/s)

CF

RS

L W

ind

Spe

ed (

m/s

)

HRD Modeled Wind Speed (m/s)

JPL

Win

d S

peed

(m

/s)

SeaWinds Rev. 03934, Sept 16, 2003 02:52 Z

JPL Wind Field CFRSL Wind Retrieval

QuikSCAT vs. H* Wind Analysis

SeaWinds vs. HRD Model

CFRSL AlgorithmComposite Wind Speeds

Conclusion Ready to test current algorithm in operational

environment Acceptable estimates of high rain rates inside

storm conditions Reasonable wind speed retrievals up to 40 - 45 m/s

Work must be done to improve model function and rain backscatter and attenuation estimates Will utilize UMass IWRAP and SFMR data set Have simultaneous AMSR and SRad for the 2003

hurricane season