Cross polarized sar a new potential technique for hurricanes
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Cross-Polarized SAR: A New Potential Technique for Hurricanes. Will Perrie and Biao Zhang Bedford Institute of Oceanography Dartmouth, Nova Scotia, Canada. SAR-wind models. PR vs. incidence angle, from quad-polarization data.  Compared to other PR models ….

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Cross-Polarized SAR: A New Potential Technique for Hurricanes

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Cross polarized sar a new potential technique for hurricanes

Cross-Polarized SAR: A New Potential Technique for Hurricanes

Will Perrie and Biao Zhang

Bedford Institute of Oceanography

Dartmouth, Nova Scotia, Canada


Cross polarized sar a new potential technique for hurricanes

SAR-wind models

PR vs. incidence angle, from quad-polarization data.  Compared to other PR models …

PR dependence onincidence angle

We develop a polarization ratio model to improve wind speed retrievals…


Cross polarized sar a new potential technique for hurricanes

SAR PR ocean wind models

Nonlinear Least Squares fit ….

PR Model I

only incidence angle dependence

PR Model II

with additional wind speed dependence


Cross polarized sar a new potential technique for hurricanes

Mouche et al #2

Our #1model

Mouche et al #1 downwind

Dataset

Thompson et al

Mouche et al #1 crosswind

Johnsen et al

Vachon&Dobson

Elfouhaily

Our #2 model

PR

PR from RADARSAT-2


Cross polarized sar a new potential technique for hurricanes

SAR winds from CMOD5.N and our model#I + R2 HH pol image

Dataset

14.1 m/s

12.9 m/s

12.4 m/s

11.6 m/s

15.9 m/s

16.6 m/s

Zhang, B., W. Perrie, and Y. He (2011), Wind speed from RADARSAT-2 quad-polarization images using a

new polarization ratio model, J. Geophys. Res., doi:10.1029/2010JC006522.

17


Cross polarized sar a new potential technique for hurricanes

C-band models

Co-Polarization Model:CMOD5.N

HH

VV

HV

1:wind speed, wind direction, incidence angle.

2: NRCS_VV saturated under high winds.

VH

Cross-Polarization Ocean model: C-2PO

U10

U10

Correlation coefficient for C-2PO = 0.91

1: only wind speed dependence.

2: NRCS_VH not saturated under high winds.


Cross polarized sar a new potential technique for hurricanes

R2 Quad-Polarization Ocean Backscatter Measurements

Dataset

NRCS_VV, NRCS_HH

depend on incidence

angle, wind direction

NRCS_VV saturates

U10

U10

NRCS_HV, NRCS_VH

not sensitive to incidence

angle, wind direction

no NRCS_HV saturation

C-2PO corr coeff = 0.91

U10

U10


Cross polarized sar a new potential technique for hurricanes

Hurricane wind-speed retrievals with C-2PO

Hurricane Bertha – 12 July 2008


Cross polarized sar a new potential technique for hurricanes

Hurricane Ike – 10 Sept 2008


Cross polarized sar a new potential technique for hurricanes

Hurricane Bill – 22 Aug 2009


Cross polarized sar a new potential technique for hurricanes

Hurricane Danielle – 28 Aug 2010


Cross polarized sar a new potential technique for hurricanes

Hurricane Earlon Sep 02, 2010 at 22:59 UTC

VH polarization

VV polarization

RADARSAT-2 dual-polarization SAR image


Cross polarized sar a new potential technique for hurricanes

Hurricane Earlon Sep 02, 2010 at 22:59 UTC

Winds -buoy #41001 is 18.1

(m/s) C-2PO is 16.0

CMOD5.N is 17.4

H*Wind is 16.8

H*Wind (m/s)

CMOD5.N(m/s)

C-2PO model (m/s)


Cross polarized sar a new potential technique for hurricanes

Comparison of C-2PO and CMOD5. SAR wind retrievals

eyewall? rain? gradients?

Along track-SFMR (hr) time series

SFMR-measured 10s rain rates (mm/hr) time series (hr)


Cross polarized sar a new potential technique for hurricanes

Hurricane Earl

C-2PO

CMOD5.N

Comparisons of C-2PO and CMOD5.N SAR-retrieved winds U10 (Sep 02, 2010 at 22:59 UTC)with collocated H*Wind


Cross polarized sar a new potential technique for hurricanes

Hurricane Ike

dual-polarization SAR image at 23:56 UTC on Sep 10, 2008

VV polarization

VH polarization

CMOD5.N + wind directions via H*Wind

C-2PO model U10


Cross polarized sar a new potential technique for hurricanes

Hurricane Ike

C-2PO

CMOD5.N

Comparisons of C-2PO and CMOD5.N SAR-retrieved winds U10 (23:56 UTC, on September 10, 2008) with collocated H*Wind

CMOD5.N  bias of -4.89 m/s and RMS error of 6.51 m/s C-2PO  bias of -0.88 m/s and RMS error of 4.47 m/s


Summary

Summary

  • C-2PO model presented

  • insensitive to wind direction, radar incidence angle

    • easy mapping of observed cross-pol NRCS to wind speed

  • avoids errors in wind speed retrievals that occur in CMOD5.N

  • in quad-pol data, C-2PO does not seem to saturate

    • potential for hurricane wind retrievals

  • dual-pol Earl:high wind comparisons R2 SAR – airborne SFMR

  • Earl: C-2PO bias= -0.89 m/s, RMSE= 3.23 m/s, CMOD5.N bias= -4.14 m/s, RMSE= 6.24 m/s.

  • Reasons for under-estimates:

  • CMOD5.N is saturated in high winds

  • co- and cross-polarized NRCS calibration error

  • CMOD5.N and C-2PO do not account for rain, high sea states, eye gradients, e.g. dampen the NRCS  biases in wind speeds

  • inaccurate wind directions for CMOD5.N.


Some other sources

Some other sources…

  • Paul Hwang et al. TU2.T10.4 (11:20) Wind retrieval with cross-polarized SAR returns

  • Vladimir Zabeline et al. TH2.T02.2 RADARSAT Application in ocean wind measurements

    Hwang, P. A., B. Zhang, and W. Perrie, 2010: Depolarized radar return for breaking wave measurements and hurricane wind retrieval. Geophys. Res. Lett.,37, L01604, doi:10.1029/2009GL041780.

    Vachon, P.W. and J. Wolfe, (2010), C-band cross-polarization wind speed retrieval, IEEE Geosci. Remote Sens. Lett., 7, 456-459.

    Zhang, B., and W. Perrie (2010), C-band Quad-Polarization ocean backscatter measurements: A new polarization ratio model. SEASAR2010, January 25-29, Frascati, Italy.

    Zhang B., W. Perrie, and Y. He, 2011: Wind speed retrieval from RADARSAT-2 quad-polarization imagesusinga new polarization ratio model. J. Geophys. Res., 116, doi:10.1029/2010JC006522.

    Zhang, B., W. Perrie (2011), Cross-polarized synthetic aperture radar: a new measurement technique for Hurricanes, under review - Bulletin of the American Meteorological Society (BAMS).


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