Polarimetric Radiometer and Scatterometer Measurements

Simon H. YuehJet Propulsion Laboratory

Operational SVW Requirement Workshop, Miami7 June 2006

2

Outline

• Introduction• Coastal Winds off Southern California• Active and Passive Measurements for Hurricane

Erika in 1997• Combined Polarimetric Measurements in

Monterey Bay in 2000 • WindSat Signals for High winds• Summary

3

Coastal Wind off Southern California from POLSCAT/DC-8 on 17 Feb 2002

10km

4

Coastal Wind off Southern California from POLSCAT on 17 Feb 2002

After about 4 hours, wind speed increased by about 4-5 m/s

5

Polarimetric Radiometry

• Microwave emission from sea surfaces is polarized and varies with ocean surface wind speed and direction

• Stokes vector describes the full polarization properties of polarized radiation

• Measurement techniques– Coherent Correlation

measurements

– Incoherent power measurements

2 2

2 2

*45 45

*

2Re

2Im

v hv h

v h v h

v h

LC RCv h

E E T TIE E T TQ

IT TU E E

T TV E E

vE

hE

45E

45ERCE

LCE

6

Symmetry Properties of Polarimetric Radiometer Signals

• Tv and Th are symmetric with respect to wind direction.

• U and V are odd functions of wind direction

7

POLARIMETRIC SCATTEROMETRY

VV VHHV HH

•Polarimetric Scattering Matrix

•Polarimetric Correlation

22 ||||*

VHVVVVVH

VVVH

• Theoretical Predictions of Polarimetric Signature of Wind Direction

vv, hh, vh and hhvv are cosine functions of wind direction

hhhv and vvhv are sine functions

V

H

WindOcean Surface

Radar

8

Significance of Polarimetry and Combined Active/Passive

• Measurements

2 cos(2 )

sin( )

c

s

• Inversion

– From c2, we get φ, -φ, φ+180 and 180-φ

– From s, we get two solutions, φ and 180-φ

• Polarimetry will reduce the number of directional solutions

• Will enhance the identification of circulation

9

NUSCAT/WINDRAD Data at 35 m/s Wind Speed in September 1997

• Simultaneous 13 GHz radar and multi-frequency radiometer observations

• Radar and polarimetric radiometer data showed consistent wind direction.

NASA P-3 FLIGHT OVERHURRICANE ERIKA INSEPTEMBER 1997(AVHRR INFRARED)

10

POLSCAT/WINDRAD ON NCAR C-130

• OCEAN FLIGHTS NEAR MONTEREY, CA IN AUGUST 2000 AND JULY 2002

– STAR FLIGHT PATTERNS OVER MBARI MOORINGS

POLSCAT

Mooring

PALS WINDRAD WINDRAD

11

• Clear Wind Direction Signals in All Polarimetric Channles at 10 M/S Wind Speed

VV, HH, VH, HV, and VVHH are cosine functions

VVHV, VVVH, HHHV, HHVH are sine functions

Upwind

POLSCAT DATA FROM ONE STAR FLIGHT PATTERN Over MBARI M2 Mooring on August 16, 2000

12

Polarimetric Scatterometer and Radiometer Measurements at 11 m/s on Aug 16, 2000

0 cos(2 )

sin( )

sin( )sin(2 )cos( )

cos(2 )

VVVH

V

H

UVT

T

Upwind Crosswind

13

QuikSCAT and WindSat MatchupHurricane Isabel

Date QuikSCAT Rev

WindSat Rev Best Track Maximum Wind Speed (m/s)

Sept 8, 2003 21982 3482 56

Sept 10 22012 3510 62

Sept 11 22019 3518 65

Sept 11 22026 3525 72

Sept 13 22055 3553 72

Sept 14 22063 3562 71

Sept 14 22070 3567 69

14

WindSat 10 GHz Data for Hurricane Isabel Rev 3510

• U data show circulation around eye

15

GMF FOR VERY HIGH WIND• The Approach is based on Young’s technique (JGR 1993) for the estimate of Geosat Altimeter

wind speed algorithm• The same technique applied to the QuikSCAT data to develop the model function for very high

winds

WindSat Tb

HOLLAND’S TC MODEL WIND

LocationVelocity of forward motionCentral and ambient pressureRadius of maximum wind speedAngle of the maximum wind

b(W,)

5 m/s and 20 degree bins

16

Holland Model Direction Versus QuikSCAT Wind Direction for Isabel (QuikScat Rev 22012)

17

WindSat U and V Signals Versus Holland’s Directional Model for Rev 3510

The data from other revs have similar directional features.

18

Polarimetric WindSat Data Show Response to Hurricane Wind direction

• WindSat 10, 18 and 37 GHz data from hurricane Isabel respond to hurricane wind direction

• 10 GHz U1 data show strong response at 50 m/s or higher wind speed

19

WindSat U Model Function and Comparison with Aircraft K-band Data

• WindSat U data agree well with aircraft data• Observable passive directional signals for

above 30 m/s

20

Summary

• Airborne scattermeter data frequently showed features with a few Km scale

• Scatterometer and polarimetric radiometer data show consistent directional signals for 20-35 m/s

• Polarimetric scatterometer signals complement the directional characteristics of VV, HH and HV NRCS

• WindSat 10-GHz U data showed directional response to ocean wind direction for 50-60 m/s winds.– There were anomalous directional features in V data

near eye