Sentinel-3 Product Notice SYNergy

Transcription

1 Sentinel-3 Product Notice SYNergy Mission Sentinel 3-A Sensor SYNERGY products (combination of OLCI and SLSTR) Product SY_2_SYN SY_2_VGP SY_2_VG1 SY_2_V10 Product Notice ID S3A.PN-SYN-L2.02 Issue/Rev Date 05/09/2018 Version 1.0 Preparation This Product Notice was prepared by the Sentinel 3 (S3) Mission Performance Centre and by ESA experts Approval ESA Mission Management Summary This is a product notice for the release of operational Sentinel-3 SYNERGY Level 2 products to user s community. The notice gives a clear indication of the current implementation for the retrieval of Surface Directional Reflectance (SDR) and Aerosol Optical Depth (AOD) parameters as well as their characteristics and potential (current) limitations. The products are currently available via the ESA S3 Expert Data Hub. ESA page 1 / 7 05/09/2018

2 Processing Baseline Processing Baseline IPF Processing Baseline: 2.39 (S3A) / 1.10 (S3B) IPFs version OL_1 IPF version: SL_1 IPF version: SY_2 IPF version: PUG version: Current Operational Processing Baseline IPF IPF Version In operations since (creation date) OL Land Centres: NTC mode: 29/08/ :33 UTC SL Land Centres: NTC mode: 02/08/ :32 UTC SY Land Centres: NTC mode: 25/07/ :25 UTC PUG Land Centres: NTC mode: 12/06/ :43 UTC ESA page 2 / 7 05/09/2018

3 Status of the Processing Baseline The IPF processing baseline 2.35 / 1.6 for the SYNERGY level 2 products includes some major corrections and improvements which are summarised below: The SYN L2 processing includes an aerosol retrieval module using co-registered OLCI and SLSTR radiometric measurements. However, to ensure the quality of this retrieval, all absorption bands and bands dedicated to cloud detection have been removed from the SYN L2 processing and are not included either in the SYN L2 products. The discarded bands are Oa13 (761,25 nm); Oa14 ( nm); Oa15 (767.5 nm); Oa19 (900 nm); Oa20 (940 nm); S4 (1375 nm). The aerosol retrieval section is performed on a macro-pixel resolution with one macro-pixel defined as a 15 by m SYN pixels. Derived aerosol data are then interpolated on the reduced 300m grid using, for each 300m pixel, data from the overlapping macro-pixel plus data from the 3 closest neighboring macro-pixels. The filtering of cloudy and snow/ice pixels has been reviewed. Any pixel detected as snow/ice or cloudy will not be taken into account in the aerosol retrieval module. Similarly, pixels in the direct neighboring of cloudy pixels (flagged as cloud_margin) are also discarded from aerosol retrieval module. However, the pixels flagged as cloudy are the only ones associated with a _Fillvalue in the final SYN L2 product. Snow or cloud_margin pixels are cosmetically filled and associated with SYN L2 data in the final product. One exception can be observed in case of extensive cloud cover. A current issue prevents macropixels including only pixels flagged with cloud, cloud_margin and cloud_ambiguous to be taken into account in the cosmetic filling module. The impact is some blockiness in the resulting SYN L2 products at the edge of the cloud mask. This issue is currently under investigation and will be corrected in the next version of the SYN processor. The cosmetic filling strategy has been reviewed. This section is performed on the macro-pixel resolution. If the aerosol retrieval failed over one macro-pixel, successful neighbors are searched in a limited area (configurable radius set to 20). If the number of successful neighbors is higher than a certain threshold (configurable parameter set to 10%), an averaging of data associated with these successful macro-pixels is performed. If the number of successful macro-pixels is below this threshold, the aerosol optical thickness is set to climatological values, extracted from the Monthly CAMS reanalysis. Inland waters are discarded from processing ESA page 3 / 7 05/09/2018

4 The VGT processing is performed after SYN L2 module and uses as input surface reflectance and aerosol data computed during this section. This data are then projected on the 1 km Plate-Carrée grid to be compliant with historical VGT products. This projection is performed by a simple averaging of all SYN L2 data included in a Plate-Carrée Box. Known product quality limitations Despite these evolutions and corrections, some choices and limitations need to be underlined : To avoid strong interfaces between the different aerosol models, and waiting for an update of the corresponding Auxiliary Data Files, only the continental model is taken into account. This limitation can create erroneous patterns over deserts or mountains. Similarly to OLCI level 2 products, camera interfaces can also be visible on some SYN L2 products. As the aerosol retrieval is supposed to be more accurate on dual-view area, a transition between nadir only and dual view area can be observed in some SYN L2 products. In a majority of products, this transition is visible through sharp differences in the Aerosol Optical thickness Values. When the OLCI orbit file starts in ascending mode, an operational issue can prevent the SLSTR data to be well-handled by the SYN L2 module. There will be then no SLSTR data in the SYN product and the aerosol retrieval will be performed using only OLCI pixels. To avoid empty SYN L2 files, only the descending orbits parts will be considered in the PDGS production. A full technical solution is currently investigated The combination of {SYN_success; SYN_aerosol_filled; SYN_AOT_climato} flags can be misleading. These flags are firstly defined on the macro-pixel resolution. Then, during the aerosol interpolation, for each 300m pixel, the flags associated with the 4 closest macro-pixels are taken into account : o If only one of these macro-pixels is flagged cosmetic fill SYN_aerosol_filled or SYN_AOT_climato, the 300m pixel is flagged accordingly. o However, the 300m pixel is flagged as SYN_success if the 4 macro-pixels are flagged as SYN_success. As consequences, depending on the used macro-pixels, a 300m pixel can be flagged by both SYN_AOT_climato and SYN_aerosol_filled. If successfully retrieved AOT values are available, those will be always used for the interpolation. However, if a 300m pixel is interpolated from 3 SYN_success macro-pixels and one SYN_aerosol_filled macro-pixel, it will be flagged as SYN_aerosol_filled and not SYN_success ESA page 4 / 7 05/09/2018

5 Note that, currently for the VGT-like products, the projection on Plate-Carrée grid is performed using a simple averaging of all 300m pixel geographically included in one box, without taking into account neighboring pixels. This computation can lead to pixelated patterns close to borders or close to cloudy area. This projection will be improved in the following months and replaced by the stretched bicubic interpolation, to be compliant with PROBA-V products (evolution planned to be released in 4 th quarter of 2018). This modification will also provide better VGT flags directly linked to this remapping and no longer linked to SYN L2 grid. Note also that the cloud and snow VGT flags are currently linked to derived SLSTR L1b nadir view cloud and snow flags and not the ones derived from specific SYN L2 cloud/snow detection module. The current Status map associated with SY_2_VG1 & V10 composite products can be misleading, specifically concerning land and missing data. If a land pixel is empty (too many clouds or corrupted radiometry associated with this pixel all along the composite period), this pixel will not be flagged as land. As consequences, it is not possible to distinguish ocean and missing pixels. A correction is currently under investigation to avoid this confusion and to better characterized each SYNERGY VGT-S pixels. Products Availability Copernicus Open Access Hub ( S3 Expert Users Data Hub Other None Any other useful information References OLCI L1 Product Notice o S3A.PN.OLCI-L1.03, v1.0 dated on 14/03/2018 o S3B.PN.OLCI-L1.01, v1.0 dated on 28/06/2018 SLSTR L1 Product Notice ESA page 5 / 7 05/09/2018

6 o S3A.PN.SLSTR-L1.04, v1.1 dated on 02/05/2018 o S3B.PN.SLSTR-L1.01, v1.0 dated on 28/06/2018 Product Data Format Specification SYNERGY Level 1 & 2 Instrument Products, Ref: S3IPF.PDS.006, Issue: 1.9, Date: 04/12/ Static ADFs S3-A S3A_SL_1_MCHDAX_ T000000_ T235959_ T MPC_O_AL_003.SEN3 S3A_SY_1_GCPBAX_ T000000_ T235959_ T MPC_O_AL_003.SEN3 S3A_OL_1_MCHDAX_ T000000_ T235959_ T MPC_O_AL_003.SEN3 S3A_SY_1_PCP_AX_ T000000_ T235959_ T MPC_O_AL_005.SEN3 S3 SY_1_CDIBAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3A_SY_2_PCP_AX_ T000000_ T235959_ T MPC_O_AL_004.SEN3 S3A_SY_2_RAD_AX_ T000000_ T235959_ T MPC_O_AL_002.SEN3 S3A_SY_2_RADPAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3A_SY_2_RADSAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3A_SY_2_SPCPAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3 SY_2_AODCAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3-B S3 SY_1_CDIBAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_SY_1_GCPBAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_SL_1_MCHDAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_OL_1_MCHDAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_SY_2_PCP_AX_ T000000_ T235959_ T MPC_O_AL_002.SEN3 S3B_SY_2_RAD_AX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_SY_2_RADPAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_SY_2_RADSAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3B_SY_2_SPCPAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 S3 SY_2_AODCAX_ T000000_ T235959_ T MPC_O_AL_001.SEN3 In red, updated ADFs ESA page 6 / 7 05/09/2018

7 End of the Product Notice ESA page 7 / 7 05/09/2018