Evaluation of sea surface salinity

observed by Aquarius

Hiroto Abe, Naoto Ebuchi

(Hokkaido University, Japan)

1

8th Aquarius/SAC-D

Science Team Meeting

(November 13th, 2013)

Objective of this study(1/1)

Validate SSS observed by Aquarius using

various salinity data including Argo observation.

2

Data (1/2) - Level 2 -

Satellite salinity

Aquarius SSS (beam1, 2, 3)

1) V2.3.1 : NASA/JPL PO.DAAC

2) CAP V2.3.1 : NASA/JPL, Dr. Simon Yueh

3) RSS V3 : Remote Sensing Systems

In situ salinity

1) Argo salinity : Global Data Assembly Center,

real-time mode data

2) TAO/TRITON, PIRATA, RAMA buoys

3

Data (2/2) - Level 3 -

Satellite salinity

Aquarius Level 3 SSS (V1.3, V2.2, V2.3.1, CAP V2.3.1)

NASA/JPL PO.DAAC

Salinity data

1) JAMSTEC Argo optimal interpolation system : MOAA/GPV

(Argo salinities are interpolated based on World Ocean Atlas 2001)

2) JMA data assimilation system : MOVE/MRI.COM

(In-situ and satellite altimeter data are assimilated into it)

4

Comparison with in situ data (1/3)

5

Aquarius (Level2) v.s. Argo float

rms difference =

0.44 psu

6

Comparison with in situ data (1/3)

1) wind speed < 15m/s

2) Argo temperature > 5C)

3) Argo depth < 12.5 dbar

4) rad_land_frac < 0.0005

5) rad_ice_frac < 0.0005

Period : 25 Aug 2011 – 31 Oct 2013

Matchup condition : 200 km, 12 h

Argo salinity (psu)

Aquarius S

SS

(psu)

V2.3.1, beam1

7

Comparison with in situ data (2/3)

Rms difference =

0.44 0.55 0.44

Aquarius S

SS

(psu)

Argo salinity (psu)

V2.3.1 CAP V2.3.1 RSS V3

beam1

Comparison with in situ data (3/3)

8

Aquarius (Level2) v.s. moored buoys

9

Comparison with in situ data (3/3)

V2.3.1 CAP V2.3.1 RSS V3

beam1

Aquarius S

SS

(psu)

buoy salinity (psu)

Rms difference =

0.43 0.49 0.47

10

V2.3.1 CAP V2.3.1 RSS V3

-0.8 +0.8 0.0

Sep. 2011

Mar. 2012

psu

Ascending minus descending seasonality (1/2)

11

CAP V2.3.1

RSS V3

60N

60S

0

The bias is small

for the CAP product.

Ascending minus descending seasonality (2/2)

J M M J S N N S

2011 2012

+0.4

-0.4

0.0

(psu)

V2.3.1 la

titu

de

J M

2013

Residual analysis (1/6) -SST-

12

Argo temperature(degC)

resid

ual (p

su)

2

-2 0

30 20 10 0

V2.3.1

RSS V3

CAP V2.3.1

residual = AQ - Argo

Residual analysis (2/6) -SST-

13

bias stddev 1.0

-1.0

0.0

0

1.0

10 20 30 Argo temperature(degC)

The stddev is large under low SST condition.

2.0

0.0

Argo temperature(degC) 0 10 20 30

V2.3.1 CAP RSS V2.3.1 CAP RSS

Residual analysis (3/6) -wind speed-

14

scatt. wind speed (m/s)

2

-2 0

20 10 0

V2.3.1

RSS V3

CAP V2.3.1

residual = AQ - Argo

resid

ual (p

su)

Residual analysis (3/6) -wind speed-

15

bias 1.0

-1.0

0.0

0 10 20

V2.3.1 CAP

stddev

1.0

2.0

0.0 0 10 20

V2.3.1 CAP RSS RSS

scatt. wind speed (m/s) scatt. wind speed (m/s)

The stddev is large under strong wind condition.

16

Rms difference is large under low SST and strong wind conditions.

The CAP product is sensitive to SST and wind speed.

V2.3.1 CAP V2.3.1 RSS V3

Argo temperature(degC)

Win

d s

pee

d (

m/s

)

rms difference

0.0

0.4

0.8

1.2

beam1

Residual analysis (5/6) -SST and wind speed-

rms d

iffe

ren

ce

(p

su

)

Residual analysis (6/6) -SST and wind speed-

17

V2.3.1 CAP RSS

Argo temperature(degC)

Win

d s

pe

ed

(m

/s)

beam1

beam2

beam3

Rms difference depends on beam for the CAP product.

Comparison with JAMSTEC Argo OI (1/3)

18

V2.3.1

JAMSTEC Argo OI (10m)

V2.3.1 – JAMSTEC Argo OI

Residual SSS is negative in

low and mid latitudes

rms is 0.25 psu (>0.2 psu)

Jan. 2012

19

CAP V2.3.1

JAMSTEC Argo OI (10m)

CAP – JAMSTEC Argo OI

Comparison with JAMSTEC Argo OI (2/3)

Negative bias is small

for the CAP product.

Jan. 2012

rms is 0.18 psu (<0.2 psu)

20

2011

Comparison with JAMSTEC Argo OI (3/3)

2012 2013

Jan. 2012

Rms difference is the smallest for the CAP product.

Rms difference (psu) (40S-40N)

Comparison with JMA assimilation system (1/3)

21

V2.3.1

MRI.COM (1m)

V2.3.1 – MRI.COM

Negative bias

rms is 0.23 psu (>0.2 psu)

Jan. 2012

22

CAP V2.3.1

CAP – MRI.COM

MRI.COM (1m)

Less negative bias

Comparison with JMA assimilation system (2/3)

rms is 0.18 psu (<0.2 psu)

Jan. 2012

23

2011 2012 2013

Rms difference is the smallest for the CAP product.

Comparison with JMA assimilation system (3/3)

Jan. 2012 Rms difference (psu) (40S-40N)

Summary (1/1)

Aquarius SSSs, retrieved by recent algorisms, were validated

using various salinity data (V2.3.1, CAP V2.3.1, RSS V3).

24

Rms difference was 0.43 – 0.55 psu.

The ascending – descending bias was small for the CAP product.

Rms difference depended on beam for the CAP product.

The negative biases found in the low/mid latitudes were small for

the CAP product.

Rms difference was 0.21 psu (CAP) and 0.23 psu (the others).

Level-2 SSS v.s. Argo, moored buoy

Level-3 SSS v.s. JAMSTEC OI, JMA/MRI.COM

25

Backup Slide

26

Comparison with in situ data (1/4)

Argo salinity (psu)

V2.3.1 CAP V2.3.1 RSS V3

beam1

Rms difference

0.44 0.55 0.44

Aquarius S

SS

(psu)

27

Comparison with in situ data (2/4)

Argo salinity (psu)

V2.3.1 CAP V2.3.1 RSS V3

Rms difference

0.46 0.52 0.47

beam2

Aquarius S

SS

(psu)

28

Comparison with in situ data (3/4)

V2.3.1 CAP V2.3.1 RSS V3

Aquarius S

SS

(psu)

Argo salinity (psu)

beam3

Rms difference

0.48 0.50 0.51

29

Comparison with in situ data (4/4)

Rms difference is large for the CAP product.

But those are mostly the same in beam3.

CAP

V2.3.1

RSS

Statistical summary

xy-plot of the collocation points (1/1)

30