Ocean Wave Slope and Galactic ReflectionSIMON YUEH

Santa Rosa, March 28, 2012

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Principle for Ocean Wave Slope Estimate

• ΔTBG varies with angular spread (or wave slope or wind speed) and position of beam in the galaxy

• For each Aquarius footprint, ΔTBG is evaluated for Gaussian beam width (B) of 5, 10, 15, 20, 25 and 30 degrees

• Use 3 months of Aquarius Beam 1 data for each wind speed range to find B(w) that minimizes the mean square difference.

( , )Bg x y sky x yT R GP T d dq q q qD = ò

B

ΔTBG

P1 P2P3

P1

P2

P3

Background figure from LeVine and Abraham, 2004

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Sensitivity of TBG to B

• ΔTBG has more variations for low B (low wind speed) near galactic plane

Low wind

Medium wind

High wind

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Aquarius B vs. Wind Speed

• B(w) estimated from v-pol and H-pol agree with each other

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Slope Model Comparison

• Larger than Cox-Munk – could this be caused by swell or long wave?

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Improvement on Salinity Retrieval Case Study 1 (High TBG and low wind)

• Use CAP algorithm to retrieve SSS using existing (red) and modified (black) TBG corrections

• Hycom SSS in green

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Improvement on Salinity RetrievalCase Study 2 (Repeat ase 1)

• Use CAP algorithm to retrieve SSS using existing (red) and modified (black) TBG corrections

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Improvement on Salinity RetrievalCase Study 3

• Use CAP algorithm to retrieve SSS using existing (red) and modified (black) TBG corrections

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Summary

• Aquarius data near galactic plane will allows the recovery of ocean wave slope

• The retrieved wave slope improves SSS retrieval, in particular by about 1 psu near galactic plane under light wind conditions

• SSS retrieval become less sensitive to errors in the wave slope estimate for higher wind speed (larger wave slope or more smearing)

• The improvement did not provide much reduction for global averaged SSS error.

• Ascending/descending bias not reduced.

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Aquarius CAP Algorithm for SSS and Wind Retrievals

• Tested the algorithms using the Aquarius V1.1 and V1.2 data

2 2 2 2 22 2 20 0 0 0

2 2 2 20 0

( )( ) ( ) ( )( , , )2 2 ( ) ( )

m mm VV VVm HH HHmpol

p VV p HH

Q U Q UI IF SSS WT T k k

s s s sfs s

+ - +- - -= + + +

D D

• CAP Algorithm: Retrieve SSS, Wind Speed and Direction Using Combined Passive and Active (CAP) Data

• Select the ambiguity closest to the NCEP winds in direction

BV BHI T T= +

BV BHQ T T= -

Yueh and Chaubell, IEEE TGRS, in press

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Comparison of V1.2.3 and CAP Salinities

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Comparison of V1.2.3 and CAP Salinities