SMOS-BEC – Barcelona (Spain) LO calibration frequency impact Part II C. Gabarró, J. Martínez, V. González, A. Turiel & BEC team SMOS Barcelona Expert Centre.

SMOS-BEC – Barcelona (Spain)

LO calibration frequency impact

Part II

C. Gabarró, J. Martínez, V. González,

A. Turiel & BEC team

SMOS Barcelona Expert CentrePg. Marítim de la Barceloneta 37-49, Barcelona SPAINE-mail: [email protected]: www.smos-bec.icm.csic.es

SMOS QWG-7 ESRIN, 31 January – 1 February 2012

LO CAL FREQ ANALYSIS

INDEX

1)BRIEF SUMMARY OF QWG-4 (March-2011) & QWG- 5 (June) RESULTS & CONCLUSIONS :

- ICM STUDY- UPC STUDY

2)NEW ANALYSIS WITH DECIMATED DATA FROM MARCH 2010 (processors v500)

2)ANALYSIS OF NOVEMBER/ DECEMBER 2011 DATA (using 2 weeks of LO=2min)

2


ICM QWG-4 STUDY

3

20100325T040821descending

TBH_10min-TBH_2min TBV_10min-TBV_2min

Decimation Study(10min, 6min and 2min)57 orbits from 24th – 25th March 2010

TB_10min-TB_2min

SMOS QWG-7 ESRIN, 31 January – 1 February 2012 4

SSS LO 10min -2min SSS LO 6min -2min

ICM QWG-4 STUDY

SSS LO 10min - 2min


6min

-2m

in

10m

in-2

min

Spatial structures appear both cross-track and along-track The structures are still present after averaging

data with decimated calibration. (Tx+Ty)/2 averaging 0 to 40º incidence angles.

UPC LO ANALYSIS

5


UPC LO ANALYSIS

10

min

-2m

in6

min

-2m

inThe LO-phase error induces structure in xi-eta

Average of 126 snapshots of TBn-TB2

6


CONCLUSIONS FROM QWG-4 & 5

•Clear impact on TB (larger in V-pol) and SSS.

•TB differences between LO-10min and LO-2min have a global STD of 0.47 K.

•LO phase drift produces non-random visibilities errors -> TB spatial structures in xi-eta.

•Relatively small phase error (low STD) may have impact on the image due to this systematic behaviour.

•Spatial structures are expected in SSS retrievals due to imperfect LO phase error cancellation.

•Differences in SSS global STD 0.48 psu.7


LO Cal Freq Analysis in QWG-7

2) DATA SET: DECIMATION STUDY

•24th-26th March 2010 (81 semi-orbits) with MIRAS at LO=2 min

•Repeated the decimitation with the newest versions of processors:• L1PP5.00 (no land-sea contamination bug)• L2PP5.00

8


Different impact across track : Spatial structures, as observed in UPC study.

SSS 10 min- SSS 2min

X-Swath (Km) X-Swath (Km)

SSS 10 min- SSS 2minAveragingAveraging

One half-orbit from Pacific(similar with many)

2) DECIMATION MARCH 2010

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3 days, 81 semi-orbitsStrong filtering (optimal conditions)World except N. Atlantic & Med.Different OTTs for 2, 6, 10 min.

• Large Reduction of STD in TB• Reduction of tails


TB 10 min- TB 2min TB 6 min- TB 2min

10

Comparing calibration at 10 min vs. 6 min

0.55 0.15


SSS 10min – SSS 2min

Latit

udin

al a

vera

ge

Lat=[45S, 30N]Bias = 0.05 psu Std = 0.11 psu

Lat=[45S, 30N]Bias = 0.05 psu Std = 0.11 psu

SSS L3 map 10 min – SSS L3 map 2 min -> 3 days, 0.5o binned

Filtered by:X-Swath < 400 kmPoor_geo & poor_ret


11



• Significant reduction of bias & Std SSS by going to 6min, reduction of tails• Accuracy req. SSS maps 0.1 psu. -> low cal. freq implies additional non negligible error!

SSS

10 m

in-

SSS

2min

SSS

6 m

in-

SSS

2min

WORLD LAT=[45S, 30N]

12

0.28

0.070.16

0.11

Comparing10 and 6 min.


3) DATA FROM NOVEMBER – DECEMBER 2011:

3 periods of 10 days have been selected (from DPGS)

•20th – 29th November : LO=10 min•6th – 15th December : LO=2 min•20th - 29th December : LO=10 min

Maps of 10 days at 4H9 have been constructed.

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Mean AVERAGE (SMOSminus ARGO)Periods of 10 days -> one every 3 days

Mean AVERAGE (SMOSminus ARGO)Periods of 10 days -> one every 3 days

high variation over timehigh variation over time

5-19 DecLO =2min

<SSS

-ARG

O>

LO effect between different periods of time is maskedLO effect between different periods of time is masked

01-10 July 2011

31 Dec, 201110 Jan 2012Mixed LO data

2min & 10 min

3) DATA FROM NOV. – DEC. 2011

L1PP500 L2PP500

L2PP550

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SSS Nov 21 to 30 (LO = 10min)- SSS Dec 6 to 15 (LO = 2min)

Latit

udin

al a

vera

ge


15

Lat=[45S, 30N]Bias = 0.25 psu -> higher than decimated

Lat=[45S, 30N]Bias = 0.25 psu -> higher than decimated


(SSS10min – SSS2min)_AB = Δ_impact_LO_AB + Δ_SSSvariability_AB + Δ_other_AB (SSS10min – SSS2min)_AB = Δ_impact_LO_AB + Δ_SSSvariability_AB + Δ_other_AB

20-29 NovLO =10min

6-15 DecLO =2min

20-29 DecLO =10min

Period A Period B Period C

Estimated withARGO measurementsEstimated withARGO measurements

Includes TEC, Sun, galaxy, instrument …Hard to estimate; we have used a

linear interpolation from AC period

Includes TEC, Sun, galaxy, instrument …Hard to estimate; we have used a

linear interpolation from AC period

TO BE ESTIMATEDTO BE ESTIMATED


To compare data from different periods it is necessary to consider all the factors that contribute to the differences in SSS.

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4H9 L3 binned mapaveraged to 1x1 degree

4H9 L3 binned mapaveraged to 1x1 degree

low noise: candidate to detect LO contributionLat: 0N-30S Bias = -0.21Lon: 180W-90W STD = 0.34

low noise: candidate to detect LO contributionLat: 0N-30S Bias = -0.21Lon: 180W-90W STD = 0.34

highly noisyhighly noisy

highly noisyhighly noisy (SSS10min – SSS2min)_AB (SSS10min – SSS2min)_AB


Δ_impact_LO_AB = (SSS10min – SSS2min)_AB - Δ_SSSvariability_AB - Δ_other_AB

17


Δ_SSSvariability_ABΔ_SSSvariability_AB

Optimal interpolation1x1 degree

Optimal interpolation1x1 degree

Differences between OI mapsof ARGO measurementsDifferences between OI mapsof ARGO measurements



18


Δ_other_AB Δ_other_AB

high noise:LO effect will be masked

high noise:LO effect will be maskedlow noise: changes in other factors low enough

to allow assessing LO contributionLatitude: 0N-30S

Longitude: 180W-90W

low noise: changes in other factors low enough to allow assessing LO contribution

Latitude: 0N-30SLongitude: 180W-90W



19


Δ_impact_LO_AB = -0.03 bias, 0.3 stdin the most favorable case

Δ_impact_LO_ABΔ_impact_LO_AB



20

LO cal. freq. seems to impact on land contamination


Δ_impact_LO_AB in optimal situation

Lat=[30S , 0N]Lon=[180W , 90W]

Mean: -0.0320 psuMedian: -0.0318 psuStd dev.: 0.2940 psu

Δ_impact_LO_AB in optimal situation

Lat=[30S , 0N]Lon=[180W , 90W]

Mean: -0.0320 psuMedian: -0.0318 psuStd dev.: 0.2940 psu


Δ_impact_LO_ABΔ_impact_LO_AB

21

∆_SSSvariability mean = 0.0183 median = 0.0206 std = 0.1126 ∆_other mean = -0.2579 median = -0.2559 std = 0.1831


CONCLUSIONS (I)

• In previous QWG it was shown that LO impact is not negligible nor at TB neither at SSS level.• TB spatial structures in xi-eta and across track are observed Study on decimated data (3 days, March 2010) using v500:

- TB 10min – 2min:mean= 0.07 K & std=0.54 K

- SSS L3 0.5o binned maps 10min – 2min: bias = 0.08 psu & Std = 0.28 psu

Study of two different periods (Nov-Dec 2011) - Instrumental factors are much larger than LO contribution

(thus hard to estimate). However, our analysis points to a significant LO impact on SSS maps (under optimal conditions: box in S Pacific)

bias = -0.03 psu & std = 0.29 psu22


CONCLUSIONS (II)

• Evidence is limited as the data for the study are limited. However, now as before, the issue seems serious enough to be taken into account.

• Incremental studies on incremental samples of data will probably lead to more or less the same conclusions.

• Processing improvements (CW and so on) are unlikely to change this situation.

• Definitively: with 10 min LO calibration we will never meet the mission requirements over ocean

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SMOS QWG-7 ESRIN, 31 January – 1 February 2012 24

In summary:

• 10 min kills SMOS salinity requirements

• Processing options will not help

• Time to turn on Guillermo’s proposal

SMOS-BEC – Barcelona (Spain) LO calibration frequency impact Part II C. Gabarró, J. Martínez, V. González, A. Turiel & BEC team SMOS Barcelona Expert Centre.

Documents

smos qwg

study sss

icm qwg

sss retrievals

sss global std

decimation study

brief summary of qwg

tb differences