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L2OS status summary. The SMOS L2 OS Team. What does not allow SMOS by now to reach the mission requirements for OS retrieval? Background issue: low sensitivity Tb/SSS MIRAS calibration still to be improved

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l2os status summary

L2OS status summary

The SMOS L2 OS Team

smos os retrieval problems
What does not allow SMOS by now to reach the mission requirements for OS retrieval?

Background issue: low sensitivity Tb/SSS

MIRAS calibration still to be improved

Image reconstruction imperfections (side lobes impact, Sun removal, land/sea transitions, ...)

RFI in some specific ocean areas

Geophysical modelling deficiencies (galactic noise, TEC variability, roughness correction, ...)

SMOS OS retrieval problems

2

smos os retrieval problems1
What are the main issues we have to face before applying the salinity inversion scheme?

Spatial biases in reconstructed image

Variability at different time scales not due to OS variability (calibration drifts, geophysical conditions)

L1 related problems dominate the quality of retrieved salinity

SMOS OS retrieval problems

3

smos os retrieval problems2
Mitigation by L2OS as L1 post-processing:

Constant OTT built from one ascending orbit in S. Pacific (until L2OS v3.17)

Constant OTT built from 10 orbits in S. Pacific (L2OS v5.00)

OTT from 10 orbits, different ascending/ descending, and updated monthly for DPGS and every 2 weeks for reprocessing (L2OS v5.50)

SMOS OS retrieval problems

4

2012 os retrieval performance
Recent improvements in L2 processor (v5.50):

Time-varying and asc/desc differentiated OTT to mitigate residual biases and drifts

Better outliers sorting and RFI management

Improved roughness correction models

Main remaining problems related to:

Suneffects in OTT

Galacticnoisescatteringmodel

Impact of TEC variabilitywithinsnapshot

2012 OS retrieval performance

5

slide6

Reprocessing performance

SSS1 v316 unfiltered SSS1 v550 unfiltered SSS1 v550 filtered

http://www.argans.co.uk/smos/pages/products.php

6

slide7

Reprocessing performance

SSS1 v316 unfiltered SSS1 v550 unfiltered SSS1 v550 filtered

Larger impact on descending orbits due to double OTT

http://www.argans.co.uk/smos/pages/products.php

7

slide8

Reprocessing performance

10-days/1o averaged SSS

3 -12 August 2011

Zonal average SMOS-Argo

Old processors

+0.2

- 0.2

New processors

L1 v3.46 v5.04

L2OS v3.17 v5.50

by J. Martínez, ICM/SMOS-BEC

8

temporal evolution of mean ott bias
Temporal evolution of mean OTT bias

by P. Spurgeon, ARGANS

FTT#1

FTT#3

FTT#2

0K

Asc.

-4K

Temporal oscillations of meanbiases: 1 K, period ~4months

Desc.

May 2010

May 2011

Last change of Flat Target Transformation (FTT)

9

slide10

OTTs: drift in median delta TB

by P. Spurgeon, ARGANS

Max. 0.5 K

Seasonal variation of Asc – Desc biases: amplitude ~1K

10

slide11

OTTs May 2010-Dec 2011

2K

2K

STD of ascending OTTs STD of descending OTTs

all year no April-August all year only April-August

Clear disturbance due to the presence of sun alias in the FOV:

  • Ascending orbits: April to August
  • Descending orbits: Whole year except April to August

X

Y

0.2

0.2

by X. Yin, LOCEAN

11

slide12

SMOS OS validation through L3

Monthly 1º maps: regional comparisontoArgo

SMOS ascending orbits

±300 km

3-12 m/s wind

Bias - 0.04

0.02

- 0.07

- 0.15

STD0.25

0.38

0.48

0.31

SSS September 2011

SMOS (up), Argo (bottom)

by J. Boutin et al., LOCEAN

12

slide13

Global SMOS OS validation

  • SMOS OS L3 BEC map 1ox1o
  • Optimal Interpolation using WOA2009 as background
  • 15-24 Jan. 2012
  • Argo SSS interpolated at -7.5 m

SMOS - Argo

1299 points

Bias = -0.11

RMS = 0.42

by J. Martínez, ICM/SMOS-BEC

13

slide14

SSS SMOS through the years

WOA 2009

SSS anomalies

(WOA 2009)

SSS difference

2010

2011 - 2010

2010

2011

2011

2010: El niño

2011: La niña

by S. Guimbard, ICM/SMOS-BEC

smos l2os recent work
Analysis of reprocessed L1 and L2 data

Analysis of switched land/ocean LO calibration test

Identifying OTT issues and exploring solutions

New galactic noise scattering model

Use of polarimetric information for TEC estimation

Improving RFI / filtering options

Tuning roughness correction models

SMOS-Aquarius comparisons

SMOS L2OS recent work

15

slide16

Variable LO frequency calibration test analysis

LO at 2 min from 23-Feb-2012

to 23-March-2012

C. Gabarró and BEC team

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

slide17

ANALYZED ZONES

Tropics and mid-latitudes

60S:60N

Equatorial Ocean

10S:10N

Zone 126

Southern Pacific

30S:0N – 150W:120W

Zone 122

slide18

SMOS – ARGO 2012 VS 2011

LO = 2 MIN -> 2012

20120223 - 20120324

Bias = 0.3

STD = 0.5

LO=10 MIN -> 2011

20110223 - 20110324

Bias = 0.1

STD = 0.7

slide19

MEAN/STD/RMS 2011 VS 2012

122

Equatorial

S. Pacific

mean

std

std

mean

RMS

RMS

60 S – 60 N

24/3-22/4

23/1-22/2

mean

std

23/2-22/3

LO=2min

RMS

slide20

AREA 122: 30ºS – 0º/150ºW-120ºW

Feb 23 – Mar 23

LO = 2 min

2012

Jan 23 – Feb 23

SMOS measurements

ARGO measurements

Mar 23 – Apr 23

2011

2012

slide21

AREA 126: 10º S – 10º N

Jan 23 – Feb 23

Feb 23 – Mar 23

LO = 2 min

2012

Mar 23 – Apr 23

2011

2012

slide22

AREA 60º S – 60º N

Jan 23 – Feb 23

Feb 23 – Mar 23

LO = 2 min

2012

Mar 23 – Apr 23

2011

2012

slide23

Effects on the coastal areas

  • Analysis of the impact of the change of calibration frequency near the coast. Comparison before and after setting the variable LO cal. freq.

No evident impact on coastal areas

When using a variable LO cal. frequency

23

slide24

Effects on the coastal areas

  • Analysis of the impact of the change of calibration frequency near the coast. Comparison before and after setting the variable LO cal. freq.

No evident impact on coastal areas

When using a variable LO cal. frequency

Difference due to a

large wind event

conclusions
Conclusions
  • From previous decimation studies:
  • LO calibrated @10 min degrades TB wrt @2 min by 0.47 K (STD global average)
  • SSS (filtered by good retrieval flag) degrades by 0.48 psu global (0.20 psu in optimal conditions, S. Pacific)
  • The increase of usable snapshots @10 min compared to @2 min implies an error reduction of 0.008 psu
conclusions1
Conclusions
  • From variable land/ocean calibration test:
  • The anticipated 10 / 2 min differences have not been observed in the March 2012 test
  • No evidence has been found of any impact of increasing the LO calibration frequency over ocean
  • Any possible impact appears to be hidden by stronger effects on OS quality
  • The L2OS team has not reached a consensus on the advantages / disadvantages of this calibration mode
  • No recommendation is submitted to QWG concerning its operational implementation