Revealing Geophysically-Consistent Spatial
Structures in SMOS Surface Salinity Derived
Maps
Marcos Portabella, Estrella Olmedo,
Justino Martínez, Antonio Turiel
SMOS Barcelona Expert Centre
Pg. Marítim de la Barceloneta 37-49, Barcelona SPAIN
E-mail: smos-bec@icm.csic.es
URL: www.smos-bec.icm.csic.es
SMOS-BEC – Barcelona (Spain)
Outline of the talk
• SMOS L2 standard product
• Accounting for non-linearities
• New product design
• Geophysical assessment with singularity analysis
• Conclusions
SMOS-BEC
SMOS standard L2 product (I)
SMOS-BEC
SMOS standard L2 product (II)
Comparison of distribution functions (real->grey theoretical->green):
PORTION OF DISGARDED POINTS IS NOT ALLWAYS THE SAME
Nm=97
Nm=33
SMOS-BEC
Nm=137
Xi2/Nm>1.25
Xi2/Nm>1.25
Xi2/Nm>1.25
ALL THESE
POINTS ARE
FILTERED
ALL THESE
POINTS ARE
FILTERED
ALL THESE
POINTS ARE
FILTERED
SMOS standard L2 product (III)
Comparison of density functions (real->red theoretical->blue):
Nm=33
G
O
O
BAD
QUALITY D
Q
U
A
L
I
T
<5%
Y
SMOS-BEC
Nm=97
>95%
BAD
QUALITY
BAD
QUALITY
<5%
Nm=137
G
O
O
D
Q
U
A
L
I
T
Y
>95%
BAD
QUALITY
G
O
BAD
O
QUALITY D
Q
U
A
L
I
T
<5%
Y
>95%
5 / 10
Accounting for nonlinearities (I)
1.- Floor error: smaller on 1st Stokes parameter
SMOS-BEC
Accounting for nonlinearities (II)
2.- Land sea contamination and 18-day subcycle:
18-day is the (approx.) repeat subcycle of the satellite; land-sea
contamination has this inner cycle also (J. Tenerelli, private comm.)
Intra-annual
Inter-annual
Annual mean
variability
From 9-day averages
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From 18-day averages
Accounting for nonlinearities (III)
3.- Climatology may induce some biases
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Accounting for nonlinearities (IV)
4.- Some tails, many ripples  Nodal sampling
Average reduction
of std. dev.
of 0.7 K
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Accounting for nonlinearities (V)
5.- Histograms of single retrievals of SSS have
greater dispersion than expected
18-day single-angle
SSS histograms
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Design of a new product (I)
Taking into account the discussed non-linear effects,
we have designed a new L3 product:
• Daily OTT
• Derived from 1st Stokes parameter
• 18-day, 0.5º resolution
• Nodal sampling applied
• SSS is computed averaging all single-angle
SSS retrievals 3 psu around the mode of
their distribution.
We have compared it with the standard DPGS
product
SMOS-BEC
Standard 18-day binned map (CP34-BEC)
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Mean around the mode
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Standard 18-day binned map (CP34-BEC)
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Mean around the mode
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Comparison with Argo Real-Time Mode
Zone
Description
Latitude
Longitude
Global
Tropics and mid-latitudes
60S-60N
All
Tropic
Tropics
30S-30N
All
NPac
A region of the North Pacific
45N-60N
170E-140W
Z122
A region of the South Eastern Pacific
30S-0N
150W-120W
Z124
A region of the South Western Tropical Pacific
24S-10S
165E-165W
Z126
Equatorial Oceans
10S-10N
All
Z131
Southern Ocean
60S-40S
All
Z132
Intertropical Pacific
5N-15N
110W-180W
OTT
Zone used for the OTT computation
45S-5S
140W-95W
ARGO
comparison
CP34BEC
(18-d)
Mean
around
mode
Global
Tropic
Npac
Z122
Z124
Z126
Z131
Z132
OTT
Mean
-0.19
-0.20
-0.62
-0.09
-0.10
-0.22
0.02
-0.21
-0.05
Std
0.38
0.33
0.69
0.20
0.28
0.33
0.53
0.26
0.23
Nbuoys
3720
2221
66
151
372
798
566
125
295
Mean
0.03
-0.05
-0.17
0.07
0.04
-0.08
0.43
-0.06
0.25
Std
0.56
0.49
1.11
0.25
0.38
0.43
0.80
0.33
0.28
Nbuoys
4243
2602
88
155
386
842
530
125
297
SMOS-BEC
Geophysical assessment via SA (I)
What is singularity analysis?
All ocean scalars are submitted to the action of flow
advection (the same for all them) plus other dynamic effects
(specific).
The ocean is a turbulent flow, both in 3D (vertical mixing,
small scales of order of meters) and in 2D (horizontal
dispersion, important at sub-mesoscale and greater scales).
In a turbulent flow, advection creates sharp changes and
irregularities in all scalars, which may be of small amplitude
but are well characterized by a dimensionless scalar field: the
singularity exponents field (denoted by h).
Singularity analysis is a sophisticated mathematical
technique to extract singularity exponents from maps of a
given scalar.
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Geophysical assessment via SA (II)
What is SA useful for?
Singularity exponents of different ocean scalars must correspond,
so they can be used to assess the quality of different products
h = 0,15
SSS
SST
SMOS-BEC
SMOS-BEC
Standard 18-day binned map (CP34-BEC)
SMOS-BEC
Mean around the mode
SMOS-BEC
SMOS-BEC
SMOS-BEC
Standard 18-day binned map (CP34-BEC)
SMOS-BEC
Mean around the mode
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Conclusions
• Many on-linear effects impact SSS retrievals in
SMOS.
• We have made an effort to reduce those effects
and to create new maps as less biased as possible.
• When compared to Argo, the new maps are
globally less precise (greater. std. dev.) but more
accurate (smaller bias)
• Singularity analysis reveals consistent geophysical
structures in the new products.
SMOS-BEC
GUI Singularity Analysis
Singularity Analysis Web Service is now operational (registered users)
http://cp34-bec.cmima.csic.es/CP34GUIWeb/
SMOS-BEC
27 / 10
SMOS-Mission Oceanographic Data Exploitation
SMOS-MODE
www.smos-mode.eu
info@smos-mode.eu
SMOS-MODE supports the network of SMOS ocean-related R&D
Last meeting during 2nd SMOS Science Conference (May 2015)