An ESA-DUE project

1. GLOBAEROSOL An ESA-DUE project Óscar Pérez Navarro (GMV), Celestino Gómez Cid (GMV), Irene Más Muñoz (GMV), Óscar Portela Arjona (GMV), Richard Siddans (RAL), Caroline Poulsen (RAL), Don Grainger (Oxford University), Gareth Thomas (Oxford University), Yves Des-Champs (MERIS Consultant).

2. GLOBAEROSOL • Aim is to deliver a 10 year dataset of satellite aerosol data to contribute to climate and air quality applications. • Globaerosol is a consortium of: • GMV- Spain. • Project lead and processor implementation • RAL (Rutherford Appleton Laboratory). UK • Developing SEVIRI algorithm & validation • Oxford University- UK • ATSR-2 & AATSR algorithm & validation • Yves Des-Champs as MERIS Consultant GLOBAEROSOL an ESA-DUE Project

3. GLOBAEROSOL • The project covers the following activities: • Development of a satellite data processing system to generate multi-year global aerosol product (GAP) over land and water, from European satellite instruments covering 1995-2005. • Validation of the GAP using independent ground-based measurements. • Intercomparison of the GAP with other satellite-based aerosol data sets. GLOBAEROSOL an ESA-DUE Project

4. GLOBAEROSOL • The User Group setting product requirements includes: GLOBAEROSOL an ESA-DUE Project

5. GLOBAEROSOL • The Global Aerosol Products will comprise • Aerosol optical depth at 0.55 and 0.87 microns • Angstrom coefficient • Information on speciation • At 10km spatial resolution (sinusoidal grid). • Produced from • ERS2 ATSR-2 (1995-2001) • Envisat AATSR (2002-2005) • Envisat MERIS (2002-2005) • MSG SEVIRI (2004-2005) • Individual sensor products will be provided as well as a merged daily product which combines information from all sensors • MERIS data is taken directly from the ESA operational product • ATSR-2, AATSR and SEVIRI aerosol information is retrieved by GlobAerosol using the Oxford-RAL Aerosol and Cloud (ORAC) scheme GLOBAEROSOL an ESA-DUE Project

6. GLOBAEROSOL The project is divided in two phases: • Phase I is devoted to analyze user requirements and developing a system that generates global aerosol products to meet those requirements. • Major outputs of this phase are • Fully implemented processing chain (at GMV) • Validated aerosol products for a 5 week test period • 27 August 2004 to 30 September 2004. • Validation report detailing the validation results to be circulated to potential users • Feedback from the users on the suitability of the products for their application • This phase is close to completion. • Test products and report will be made available to interested users by mid June • Anyone interested please contact us. • Phase II will then center on the production of the full 10 year product and its more extensive validation • The complete product is expected to be available by mid 2008 GLOBAEROSOL an ESA-DUE Project

7. GLOBAEROSOL • ATSR-2, AATSR and SEVIRI aerosol products are derived using the Oxford-RAL Aerosol and Cloud (ORAC) retrieval scheme. • The scheme uses the optimal estimation method. • The forward model uses the DISORT radiative transfer model in conjunction with a set of aerosol models based on a subset of the same aerosol classes used in the MERIS retrieval. • MARITIME, URBAN, BIOMASS, CONTINENTAL and DESERT DUST • The aerosol retrieval makes use of the visible channels only: • ATSR-2: 0.67, 0.87, 1.6 μm • AATSR: 0.55, 0.67, 0.87, 1.6 μm • SEVIRI: 0.64, 0.81, 1.6 μm • To provide an estimated speciation, the retrieval is repeated for each aerosol class and the model which best matches the measurement is selected. • ORAC has already been used extensively for ATSR cloud retrievals and the aerosol retrieval is currently being used in the GRAPE* project. • Adaptation of the scheme to SEVIRI has been carried out within GlobAerosol. • *See http://www-atm.physics.ox.ac.uk/group/grape/ • and http://www.badc.nerc.ac.uk/ GLOBAEROSOL an ESA-DUE Project

8. GLOBAEROSOL • Four different types of processing can be found within Globaerosol: • IOAPs (Individual Sensors Orbit-based Aerosol Products): generated DAILY • IGAPs (Individual Sensor Global Aerosol Products): generated DAILY • MGAPs (Merged Sensors Global Aerosol Products): generated DAILY • Statistical Products: From MGAPs or IGAPs: generated Weekly, Monthly, Yearly. • Individual sensor products are merged by • Applying quality control criteria to the original retrievals • Performing bias correction based on the results of validation against aeronet data. • Calculating a weighted mean of the retrieved AODs, accounting for the errors specific to each instrument / observing condition • Angstrom coefficient is then computed from the merged AODs at 0.55 and 0.87 microns • All the output products are in NetCDF format following CF conventions. GLOBAEROSOL an ESA-DUE Project

9. IOAP Generator AATSR IOAPs ATSR-2 GlobAerManager ORAC HDF Files MGAPS MERIS Merging Generator IGAPS Merging Algorithm SEVIRI DAILY Generator AUX Data* Statistical Statistical Generator GLOBAEROSOL • Schema of GlobAerosol Processing * ECMWF, Cloud Mask, MODIS, LUTS GLOBAEROSOL an ESA-DUE Project

10. Sunglint at noon 0 0.4 0.8 0.55µm SEVIRI AOD 0.55µm MODIS AOD GlobAerosol: SEVIRI / MODIS Monthly mean comparison GLOBAEROSOL an ESA-DUE Project

11. ATSR-2 comparison with MODIS and MISR GLOBAEROSOL an ESA-DUE Project

12. GLOBAEROSOL • Validation by comparison with AERONET • Period to be validate: 27 August 2004 to 30 September 2004. • The validation uses 44 stations available for the period to be validated • The intention is to overcome the inherent difficulty of comparing point measurements from the ground with spatially averaged satellite data, both taken at slightly different times, by assuming the spatial and temporal variability of the two datasets is correlated (though winds). GLOBAEROSOL an ESA-DUE Project

13. GLOBAEROSOL • Validation by comparison with AERONET • Pixels are selected within a region on ±20 km from each station (from a 10km resolution grid). • All aeronet measurements for the given ground station are extracted with time ±DT of the satellite overpass. The baseline for DT is 30 minutes (which given a typical aerosol transport speed of 50km/hour is consistent with the 50km spatial distance sampled from the GlobAerosol GAP if DP is 2). An aeronet measurement both before and after should be available. • The parameters compared are: • Aerosol optical thickness (AOT), at wavelengths, 550 and 865 nm. • Angstrom coefficient. GLOBAEROSOL an ESA-DUE Project

14. All available Aeronet sites Sea/coastal sites Comparison with Aeronet ground-based sun-photometer data with SEVIRI GLOBAEROSOL an ESA-DUE Project

15. Time-series of one site Comparison with Aeronet ground-based sun-photometer data with SEVIRI GLOBAEROSOL an ESA-DUE Project

16. Comparison with Aeronet ground-based sun-photometer data with MERIS AOD870 AOD550 Ángstrom Aerosol Index GLOBAEROSOL an ESA-DUE Project

17. GLOBAEROSOL Conclusions • GlobAerosol will deliver a 10 year aerosol dataset based on ATSR-2, AATSR, MERIS and SEVIRI. • Products from the individual sensors for a 5 week test period have been produced and validated. • ATSR-2, AATSR & SEVIRI are performing well • New version of MERIS data should address the quality issues in previous version. • Work on the merging scheme is close to completion. • Data for the test period and a report describing its validation will be made available in mid June to all interested users & we welcome feedback. • There will be a workshop [Mid July-Beginning September] • Please contact us if you are interested in receiving the test products. • Processing of the complete 10 year period is set to follow the user consultation exercise and should be completed by early 2008. Visit GlobAerosol web site: www.globaerosol.info or Contact Simmon.Pinock@esa.int, oopn@gmv.es, rsiddans@rl.ac.uk,gthomas@atm.ox.ac.uk GLOBAEROSOL an ESA-DUE Project

18. Thank you Óscar Pérez Navarro GS/DP Business Unit Email: oopn@gmv.es www.gmv.com