OSI-SAF VIIRS SST Pierre Le Borgne, Gérard Legendre, Anne Marsouin, Sonia Péré, Hervé Roquet...
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Transcript of OSI-SAF VIIRS SST Pierre Le Borgne, Gérard Legendre, Anne Marsouin, Sonia Péré, Hervé Roquet...
OSI-SAF VIIRS SST
Pierre Le Borgne, Gérard Legendre, Anne Marsouin, Sonia Péré, Hervé Roquet Centre de Météorologie Spatiale, Météo-France, Lannion, France
With contribution of Alexander Ignatov, NOAA
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Outline
Objectives Operational chain overview and status Quality Level definition Algorithm determination Validation results Conclusions
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Objectives
CMS is commited to produce SST over the NAR area for the EUMETSAT/OSISAF
We aim to start delivering operational L3C products (GDSV2.0 compliant in netcdf 4) in mid 2013
The VIIRS SST chain will be a test chain for our next operational METOP/AVHRR SST chain
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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The OSI SAF VIIRS SST chain overview
ExperimentalOE SST
Radiometric data
Maia cloud mask
Cloud mask controlNo masking!
Multispectral SST calculations
Granule workfile
Algorithm correctionNWP profilesEvery 86 s granule
Remapping and format
NAR SST product MDB
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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From radiom. dataTo workfile
From workfile to NAR
MDB extraction
Buoy!
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Adjacency algorithm
VIIRS pixel neighborhood is needed for:– T11-T12 smoothing
– Gradient computation
– Matchup Database extraction
Trimmed pixels and scan overlapping must be taken into account -> adjacency algorithm needed!
JPSS OAD document for Common Adjacency Software describes the common Adjacency algorithm
An extended algorithm has been derived to allow neighborhood determination to extend beyond adjacent scans
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Raw data
Pixel of interest
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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After local adjacency has been determined
Pixel of interest
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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OSI-SAF VIIRS SST chain: status
Preoperational since mid October 2012
Cloud mask control completed
Final product ready (GDSV2.0 in netcdf4 )
Operational delivery to start in mid 2013
NWP derived correction will be introduced afterwards
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Quality levels?
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Quality levels
?
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Indicators
?
Error as a function ofTs-clim. Minimum,On the MDB
Gradient indicatorAerosol indicatorIce indicator…..
Mask indicator= mean of all indicators
Limit valueCritical value
Indicators defined between 0=clear et 100=cloudyBy limit and critical values such as:
Tlimit-TsTemp. Indicator= -------------- x 100
Tlimit-Tcritical
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Quality levels
Cloud mask indicator : mean of all indicators– Temperature indicator (distance to minimum SST clim)
– Gradient indicator (distance to maximum SST gradient clim)
– Dust indicator (derived from SEVIRI SDI)
– Ice indicator (derived from OSI SAF ice information)
Algorithm risk:– Derived from algorithm potential problems
Mask indicator
Algorithm risk
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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VIIRS SST field on the 20 March 2013 at 02:00
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Undetected cloudiness
VIIRS SST – Minimum SST Climatology (OSTIA) 20 March 2013 at 02:00
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Cloudiness detected by low SST values
Temperature indicator derived from the SST- mini clim difference 20 March 2013 at 02:00
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Cloudiness detected by high gradient values
VIIRS SST gradients on the 20 March 2013 at 02:00
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Univ. Rhode Island Pathfinderderived maximum gradient climatology
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Climatology missing
Erroneous location of max gradients
Gradient indicator
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Mask indicator (mean of all indicators)0= no risks; 100=critical
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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SST confidence levels:Increasing quality from 2 to 5
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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VIIRS SST field on the 22 September 2012 at 13:00
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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VIIRS SST – Mean SST Climatology (OSTIA) 22 September 2012 at 13:00
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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SEVIRI derived SDI
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Dust indicator
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Algorithm determination
RTTOV-10 applied on the SAFREE (radiosonde profiles) data base
Daytime algorithms NLC : SST = (a + b S) T11 + (c + d Tsclim + e S) (T11 - T12) + f S + g (1)
Night-time algorithmsT37_1 : SST = (a + b S) T37 + (c + d S) (T11 - T12) + e S + f (2)where :
– TSclim = first guess climatologic SST
– S = 1/cos () – 1
In practice T11-T12 are smoothed in a 11x11 pixel box
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Overall validation results
NAR area; 15 October 2012 till 15th March 2013Qual levels 3-5
Daytime qual. 3-5
Daytime qual. 5
Nighttime qual. 3-5
Nighttime qual. 5
number of cases
3088 990 3648 1678
bias -0.13 -0.10 -0.05 0.03
standard-deviation
0.46 0.34 0.37 0.29
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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NPP/VIIRS cloud detection is more efficient than the equivalent NOAA-A9/AVHRR
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Overall validation results:Daytime
Qual 5: =-0.10; =0.34
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Overall validation results:Nighttime
Qual 5: =0.03; =0.29
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Conclusion
A VIIRS SST chain has been run in preoperational mode since mid October 2012
Validation results are OK– Cloud free coverage significantly larger than NOAA-19
– Daytime and nighttime standard deviation: 0.46 and 0.37 K resp.
Next phases:– Starting operational delivery (mid 2013)
– NWP derived BT simulations and bias correction/Optimal Estimation
SPIE Defense, Security and Sensing, Baltimore, 29 April-3 May 2013
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Example of a granule over NE Atlantic…..
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THE END
….Remapped at 1 km resolution over Brittany