Update on S3 SYN-VGT algorithm status Status of the S3 ... · In situ data provided by AERONET Stations (D. RAMON, HYGEOS) 2. Satellite data provided by PROBA-V (C. TOTE, VITO) SYN

© ACRI-ST | S3MPC – 2014-2016

Update on S3 SYN-VGT algorithm status Status of the S3 Global Aerosol processing

PROBA-V

QWG 7 – 04/05/2018

2 © ACRI-ST | S3MPC – 2017 Proba-V QWG 7| ACRI-ST | 03-04 – May - 2018

• Status and Evolution of the SYN L2 and VGT-like processing and products Improvements since last QWG

Quality assessment made by S3MPC

Planned evolutions

» Improvement of SYN L2 products

» Alignment with PROBA-V

• Status of S3 Global Aerosol New Products


Summary of previous PROBA-V QWG

Status on last PROBA-V QWG :

Inclusion of a specific SYN L2 cloud detection module

Removal of OLCI/SLSTR channel perturbing the aerosol retrieval module

Improvement of the Cloud mask with less over-flagging and no more parallax effect

Correction of the over-estimation of the AOD, implying also a correction of the over-correction of the SDR

Updated SYN L2 processor delivered in December 2017, taken into account in operations since 11/01/2018

Global reprocessing of 1 week of data (1-7 November 2016) – Quality assessment performed by S3MPC team


RGB image Derived L1b cloud masks SYN NN cloud mask

Impacts of these evolutions


0,4

6

2,0

8

Impact of these evolutions

Previous SYN L2 product - 19/06/2017

SDR @ 490 nm

SDR @620 nm

SDR @ 708.75 nm

SDR @ 865 nm – OLCI

SDR @ 865 nm – SLSTR nadir

SDR @ 865 nm - SLSTR oblique

Figure 1 : Surface directional Reflectance associated with different OLCI and SLSTR channels from

S3A_SY_2_SYN____20170619T101637_20170619T101937_20170621T033649_0179_019_065_2160_LN2_O_NT_

002.SEN3. The unfilled land pixels are the one associated with a negative surface directional reflectance

AOT @ 550


SDR @ 490 nm

SDR @620 nm

SDR @ 708.75 nm

SDR @ 865 nm – OLCI

SDR @ 865 nm – SLSTR nadir

SDR @ 865 nm - SLSTR oblique

Impact of these evolutions

AOT @ 550

0,4

6

Current SYN L2 product - 19/06/2017


Impact on VGT-P products BEFORE - Australia


Impact on VGT-P products AFTER - Australia


SYN L2 Quality Assessment

S3MPC SYNERGY team : Comparison between SYN L2 / VGT-like products with

1. In situ data provided by AERONET Stations (D. RAMON, HYGEOS)

2. Satellite data provided by PROBA-V (C. TOTE, VITO)

SYN L2 products (Using an appropriate combination of flags discarding cloud

contamination):

Quality of SYN L2 SDR acceptable.

Correlation between SYN AOT and AERONET AOT get closer to quality standard.

High biases observed for both data; some cloud contamination need to be filtered


SYN L2 Quality Assessment

S3MPC SYNERGY team : Comparison between SYN L2 / VGT-like products with

1. In situ data provided by AERONET Stations (D. RAMON, HYGEOS)

2. Satellite data provided by PROBA-V (C. TOTE, VITO)

SYN VGT-P like products : High correspondence between SYN TOA reflectance and PROBA-V ones

Regression slope close to 1 comparing the BLUE, Red and NIR radiometric measurements.

0n SWIR measurements, systematic large differences


Remaining issues or limitations

Pixel filtering and flagging 1. Cloud contamination







2. Snow cover

3. VGT flags and transferring SYN flagging information in VGT-like products

Aerosol parameters 1. One aerosol model = continental one

2. Climatological values still dependent on latitude (CAMS climatology not yet included)


Planned evolutions

Two activities : 1. SYN L2 improvements

2. Alignment with PROBA-V

Currently under consolidation/implementation

Planned to be delivered May/July 2018


Planned evolutions

SYN L2 improvements:

1. Improvement of the Aerosol interpolation module (i.e. transferring the aerosol information from macro-pixel to 300m pixel)

2. Two cloud masks, based on SYN NN approach. More strict before the aerosol retrieval than before product formatting

3. Snow pixels discarded from aerosol retrieval module but included in SYN L2 products after cosmetic filling

4. Modification of the reference climatology – CAMS reanalysis

Less cloud contamination

Better pixel filtering implying better aerosol retrieval results

Smoother L2 products with less sharp differences


Planned evolutions

Alignment with PROBA-V:

1. Correction of VGT flags and Better handling of the inputs with a transfer of the SYN L2 flags

2. Updated Approach for Projection on Plate Carrée + modification of the status map computation

3. Updated Composite Methods with the addition of specific selection rules


VGT Band mapping and Pixel filtering

Better handling of inputs: OLCI Quality flags and SLSTR Exception/confidence flags taken into account

A. To filter the radiances used in this module

B. To define the quality flag of VGT channels

Pixel filtering: Uncertain flag initialised to FALSE

VGT flags initialised with SYN L2 flags (cloud, ice_or_snow), then if not raised, VGT tests are applied

Cloud shadows – not planned for the moment


1 km Plate Carrée Projection

Radiometric measurements

Stretched bi-cubic interpolation + filtering regarding VGT_good flag

Flags

tests on the Sum of weights computed from Stretched bi-cubic interpolation

Others measurements

nearest approach


Composite methods

Addition of several filters before choosing the maximum NDVI

Preferred Pixel Alternative option 1 Alternative option 2 or

comment

TEST 1 All spectral band available

Covered only by few VGT bands

TEST 2 B0, B2 and B3 bands « GOOD »

« BAD » radiometric values

No test on MIR channel

TEST 3 Clear sky pixel Ice/snow pixel Cloudy pixel

TEST 4 SZA « Good », SZA « Acceptable » SZA « bad »

TEST 5 Max NDVI

© ACRI-ST | S3MPC – 2014-2016

Status of the S3 New Products dedicated to Global Aerosol


Sentinel 3 Land aerosol product

Currently processed by Sentinel 3 PDGS in NTC:

OLCI L1B FR

SLSTR L1B RBT

SYN L1/L2 Processor

SYN L2 (SDR + AOT)

SYN L2 VGT-P like

SYN VGT-S Processor SYN VGT-S1

like SYN

VGT-S10 like


Sentinel 3 Land aerosol product

Future production in NRT and NTC :

OLCI L1B FR

SLSTR L1B RBT

SYN L1/L2 Processor

SYN VGT-S Processor

SYN L2 (SDR + AOT)

SYN L2 VGT-P like

SYN VGT-S1 like

SYN VGT-S10 like

SLSTR L2 AOD Processor

SLSTR L2 AOD

SYN L2 AOD

SYN L2 AOD Processor


SL_2_AOD (NRT) & SY_2_AOD (NTC)

• Global products = one single file providing data over Sea and Land :

Sea pixels over entire SLSTR swath (NRT)

Land pixels over Dual view only (NRT)

Sea and Land pixels over the entire OLCI swath (NTC)

• Reduced resolution = 4,5 km

= 9*9 SLSTR 500m pixel or 15*15 SYN 300m pixels

• Designed to follow as far as possible recommendations of the ESA Aerosol CCI website


Future Sentinel 3 Aerosol products

1 single file providing :

• Same content + {SDR, AOD, AOD_uncertainty, SSA} @ 440 nm

Under development

Delivery to PDGS planned end Q2 2018

SL_2_AOD SY_2_AOD

1 single file providing :

• {SDR, AOD, AOD_uncertainty, SSA} @ 550, 670, 865, 1600, 2250nm

• {FM_AOD, D_AOD, AAOD} @ 550 nm

• ANG_550_865

• Contextual information (position, time, flags, angles, …)

Delivered End of April 2018 to EUMETSAT


First SL_2_AOD images

Clear-sky image over France acquired on 19/06/2017

Aerosol Optical Thickness @ 550 nm

0, 0

0, 1

5

0, 3

1

0,1

0



Acquisition over Madagascar acquired on 03/12/2017


Single Scattering Albedo @865 nm

0

0,1

2

0,5

0

0,9

4

0,9

65

0,9

80

0,1

0



Acquisition over Brazil acquired on 05/12/2017


Surface reflectance @865 nm


Thank you for your attention

Documents

Update on S3 SYN-VGT algorithm status Status of the S3 ... · In situ data provided by AERONET Stations (D. RAMON, HYGEOS) 2. Satellite data provided by PROBA-V (C. TOTE, VITO) SYN