Post on 27-Mar-2021
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