Thomas Holzer-Popp (DLR), Stefan Kinne (MPI-M) & the Aerosol_cci team aerosol_cci

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 2 URD - sources GCOS as baseline CMUG as model-oriented update Applications: model development, assimiation, decadal forecasting, trend monitoring AEROCOM as aerosol_cci CRG Applications: process studies, trend monitoring MACC (currently added) Application: assimilation (re-analysis)

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 3 GCOS requirements Aerosol optical depth goalthreshold accuracy stability / decadeN/A resolution 1 km / daily 10 km / weekly Other aerosol properties to supplement AOD e.g. single scattering albedo accuracy 0.02 stability / decade Comprehensive ground-based independent validation -> can not be met (per pixel) by any satellite product

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 4 URD - CMUG

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 5 URD - requirements Overall user needs: Easy availability (netCDF) proven and documented quality aerosol properties should identify aerosol species linked to source categories observation of long-term trends (many years) for regions and globally analysis of specific issues (absorption, aerosol above clouds, vertical profile, …) prepare for easy and complete re-processing with new versions

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 6 URD - requirements Level2 products for data assimilation: AOD at 4 wavelengths (440, 550, 670, 870 nm) and several layers 500 (1000) observations per hour years covered 20 km ( 5 km) horizontal 3 km vertical accuracy and precision 0.05 (0.02) with pixel level uncertainty (random + systematic) consistent with clouds and fire

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 7 URD - requirements Level3 products for process studies and trend monitoring: AOD at 4 wavelengths Angstrom coefficient ( ), fine mode fraction (D<1μm), dust fraction Absorption aerosol optical depth (or single scattering albedo) aerosol vertical extinction / AOD profile (any information is valuable) accuracy: combined absolute (low AOD) and relative (high AOD) error characteristics

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 8 URD - requirements derived stability need regional AOD range (0.1 – 0.5) * 5% trend detection -> 0.005

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 9 URD - requirements Satellite variable (reference dataset) required RMS at superpixel level of 10x10 km 2 required RMS at climate model grid level of 1°x1° required RMS at regional level of 1000x1000 km 2 Aerosol optical depth at 550nm and other wavelengths (Aeronet global dataset daily mean) 20% or % or Fine mode fraction (Aeronet global dataset daily mean) 20% or Dust fraction (Coarse fraction from Aeronet global dataset in known dusty conditions daily mean) 30% or 0.2 Absorption optical depth (Absorption optical depth computed from SSA and size of Aeronet daily mean) 20% or % or

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 10 URD - requirements Satellite variable (reference dataset) required monthly RMS month-to-month stability at regional level of 1000x1000 km 2 required monthly RMS year-to-year stability at regional level of 1000x1000 km 2 required monthly RMS decadal stability at regional level of 1000x1000 km 2 Aerosol optical depth at 550nm and other wavelengths (Aeronet regional mean) Fine mode fraction (Aeronet global dataset daily mean) 0.05 Dust fraction (Coarse fraction from Aeronet global dataset in known dusty conditions daily mean) 0.05 Absorption optical depth (Absorption optical depth computed from SSA and size of Aeronet daily mean)

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 11 URD - consistency With CMUG requirements Same basic parameters CMUG gives higher priority and detail to vertical information CMUG adds depolarisation ratio Aerosol_cci adds aerosol type properties horizontal / temporal resolution: CMUG one dimension more demanding aerosol_cci adds regional level accuracy aerosol_cci links to horizontal resolution and adds relative criterium aerosol_cci has lower goal for aerosol type variables agreement on regional level for AOD, difference for AAOD stability aerosol_cci defines target per temporal analysis grid agreement on decadal level for AOD, difference for AAOD

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 12 URD - colocation Done in URD Done through discussions within AEROCOM Iteration with CMUG, WMO-GAW SAG and other CCIs initiated, more iteration with AEROCOM to do Is taken into account Done through WMO-GAW SAG (membership of several aerosol_cci partners) Template from ESA used and published on project website Iteration with CMUG ongoing (March meeting) MACC input upgraded Done in PSD

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 13 URD - evolution Aerosol_cci URD_v1.3 accepted Continuing iterations adding MACC data assimilation requirements (v1.4) Further iteration with other ECVs to complete their requirements Feeding aerosol_cci URD into WMO-GAW SAG aerosol input to GCOS aim to harmonize between different requirements –> iteration with contributors SAG chair: “The aerosol_cci document is far superior to anything else that I have seen concerning requirements.” – including CMUG table Apreaciates tying to applications (CMUG) and accuracy resolution-dependance (aerosol_cci)

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 14 URD - harmonization SAG chair questions and recommendations overall process use the WMO RRR excel sheet to avoid missinterpretations and gapsWMO RRR excel add 1 line for each application / resolution questions can we harmonize application domains? can we harmonize / justify vertical layers (3km – 5km)? CMUG: Why 2 values for accuracy and precision? CCI: 1° x 1° : not equal area / shall we restrict requirements to level2 products? recommendations add duration, coverage (for process studies) add requirements for sub-orbital data (model/sat validation, assimilation)

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 15 PSD - overview Product nameParameter(s)sensorslevelcomment Tropospheric / total column products Single-sensor AOD / type Multi-spectral AOD Aerosol type probability ATSR-2 / AATSR MERIS POLDER Level2,3Multi-spectral AOD depending on instrument capabilities. Ångstrom coefficient can be derived from multi-spectral AOD. Aerosol type may include information on fine / coarse mode fraction and chemical components, which together best describe the observations Synergetic AOD / type Multi-spectral AOD Aerosol type probability AATSR/SCIAMACHY ATSR-2/GOME AVHRR/GOME-2 Level2,3 AAIAbsorbing aerosol index averaging kernel OMI SCIAMACHY GOME Level2,3 Merged AOD / typeMulti-spectral AOD Aerosol type probability Combining several level2 with appropriate wighting Level3 Aerosol type “climatology” Aerosol type probability / dominant aerosol type All AOD productsLevel3Based on one year of data Stratospheric products ExtinctionGridded extinction profile GOMOS (SCIAMACHY) Level3

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 16 PSD vs. URD (1) No.User requirementProduct specification response Product parameters AOD at 4 wavelengths4 AOD, depending on instrument capabilities Ångström coefficient (based on AOD at 440 and 870 nm) Implicit from 4 AODs where feasable Fine mode fraction (based on 4 AOD) Implicit from 4 AODs where feasable (dominant) aerosol speciation or dust fraction Implicit in aerosol type probability where feasable; focus of synergetic product Absorption: AAOD or SSAImplicit in aerosol type probability where feasable; focus of AAI product Extinction profileNot feasible with the sensor suite used Numerical specifications AccuracyTo be established by validation PrecisionTo be established by validation Horizontal resolution10 x 10 km 2 / 1° x 1° Temporal resolutionDaily (finer not possible with sensor suite used) StabilityTo be established by validation

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 17 PSD vs. URD (2) Data access Easy availabilityTo be taken into account in system design Long-term recordOnly partial (2 years – options to extend further) Error documentation (indicating source of error) Will be available via web portal, with metadata of each product pointing to it System specifications Easy reprocessingTo be taken into account in system design Technical specifications FormatnetCDF as required MetadataCF1-4 convention as required Gridlat-lon for level3 as required Product levelsLevel3 as required Level2 based on MACC need / assimilation Anciliary parameters Cloud fraction (also for pixels without AOD) Missing value for pixels without AOD result Local errorPixel error contained in products

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 18 Planned product use Model development and inter-comparison -> AEROCOM Data assimilation -> MACC (as far as possible) Trend monitoring: only later (longer dataset needed) options proposed for larger dataset processing

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 19 ECV consistency Other ECV participants in Aerosol_cci algorithm workshops cloud masking (cloud, fire, landcover, ozone) surface treatment (oceancolour, landcover, fire) aerosol model -> interest of other ECVs to get our recommendation / tech note) Consistent 3-level cloud masks with cloud_cci Need recommendations from oceancolour_cci and landcover_cci for chlorophyll / sediments and BRDF auxiliary datasets + reference data exchange of URDs between ECV aerosol_cci URD distributed to CMUG and ECVs -> collect further requirements aerosol_cci contributed to cloud_cci URD

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 20 Product uncertainties Known uncertainty contributors cloud screening surface treatment (assumed) aerosol optical properties radiometric calibration pixel size /atmospheric noise radiative transfer / look-up tables Characterization of uncertainty contributions production of test datasets (1 month) with different algorithm versions harmonization of critical modules for round robin – where possible

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 21 Product uncertainties Error sourceAbsolute error contributioncomment calibrationTBDCan be critical Radiative transfernegligibleError due to Mie calculations for dust TBD Noise due to pixel size0.05Varies for different continents Cloud fractionTBDValidation showed that pixels up to cloud fraction of 35% can be exploited for the retrieval Surface reflectanceLand: 0.05 – 0.15 (for visible surface reflectance from 0 – 0.25) Ocean: 0.03 – 0.1 (for visible surface reflectance from 0 – 0.05) Choice of wrong aerosol type (spectral extinction, absorption, phase function) 0 – 0.2 for AOD – 1.Is estimated for each pixel by identifying ambiguous aerosol types through comparing quality of fit with difference between aerosol types with similar spectra) An example: synergetic retrieval algorithm (first estimation based on validation results)

Aerosol_cci > Thomas Holzer-Popp > ESA Living Planet Symposium, Bergen, 1 July 2010 slide 22 ECMWF data needs These have already iterated with D. Tann -> aerosol_cci DARD ECMWF Code Output field UnitsAnalysis or ForecastModel levelsModel GridNeeded for 16510m east wind componentm s -1 AnalysisSurfaceGG (N128)EO retrieval 16610m north wind componentm s -1 AnalysisSurfaceGG (N128)EO retrieval Parameters from ERA Interim, Atmospheric model, Analysis o Requested analysis times: 0000, 0600, 1200, 1800 UTC o Dates: 01/01/1997 to 31/12/1997; 01/10/2008 to 31/12/2008 o Requested representation: Lat/long grid o Requested representation: 0.7 degree o Requested area: Global Grib numberGrib AbbreviationUnitsName 16510Um s -1 10m east wind component 16610Vm s -1 10m north wind component