Documentation for Users of the Aerosol_cci ECV products
The Climate Research Data Package (CRDP) contains the latest / best and most complete + validated datasets of Aerosol_cci. All datasets cover at least the “golden year” of the Aerosol_cci products 2008. In addition, for mature products from sensors with predecessor instruments (i. e. ATSR-2 for AATSR) an additional dataset for the year 2000 is provided. A complete time series is provided for one algorithm for AATSR (Swansea algorithm, version 4.1; 2002 – 2012). All products provide global coverage except at high latitudes and in some cases except deserts; 2 products cover only ocean; three products are flagged as experimental since they require significant further development (BAER, ESA MERIS-standard, SYNAER).
Aerosol_cci offers 3 categories of products:
- Total column aerosol optical depth (AOD) and Ångström coefficient (AC)
- Total column absorbing aerosol index (AAI)
- Stratospheric extinction profiles and stratospheric column aerosol optical depth
In-depth analysis of the eight AOD algorithms was made and is summarized in Popp, et al., RS, 2016 (doi:10.3390/rs8050421), Holzer-Popp, et al., AMT, 2013 (doi:10.5194/amt-6-1919-2013) and de Leeuw, et al., RSE, 2013 (DOI: 10.1016/j.rse.2013.04.023). The following documentation is publically available to support understanding the products:
- User requirements document: http://www.esa-aerosol-cci.org/?q=webfm_send/1150
- Archive of mature algorithm ATBDs: http://www.esa-aerosol-cci.org/?q=webfm_send/1152
- Archive of experimental algorithm ATBDs: http://www.esa-aerosol-cci.org/?q=webfm_send/1152
- Comprehensive error characterisation report: http://www.esa-aerosol-cci.org/?q=webfm_send/975
- Product validation and intercomparison report: http://www.esa-aerosol-cci.org/?q=webfm_send/1069
- Product user guide: http://www.esa-aerosol-cci.org/?q=webfm_send/1112
- Climate Assessment Report: http://www.esa-aerosol-cci.org/?q=webfm_send/1114
- a report on analysing the consistency of cloud masks between Aerosol_cci and Cloud_cci (draft): http://www.esa-aerosol-cci.org/?q=webfm_send/507
- User requirements update form: http://www.esa-aerosol-cci.org/?q=webfm_send/1150
Following notes shall be taken into account:
- All AOD algorithms use a common definition of 4 basic aerosol components (fine mode extremes of weak and strong absorption, sea salt and mineral dust [de Leeuw et al, 2013]) externally mixed according to each algorithms strategy
- The consistency of the cloud masks used in Aerosol_cci against Cloud_cci (AATSR AOD) was assessed showing below 1% of inconsistent pixels (analyzed erroneously as at the same time as fully cloudy and fully cloud-free) and about 20% of overall neglected pixels (containing twilight zone of mixed cases, but also missed pixels for safety from cloud contamination).
- All AOD products are provided in sensor projection (level2: sinusoidal grid) and as gridded datasets (level3: all daily, most monthly).
- AAI and stratospheric products are only provided as level3 gridded datasets.
- Validation is limited in areas with sparse reference data (open ocean, Southern hemisphere) and near clouds.
- Additional aerosol (e.g. mixing fractions between the 4 components) and diagnostic (e.g. cloud, surface fit quality) parameters are contained in the product files, but have not been validated and are therefore not listed.
- All products contain pixel level uncertainties based on error propagation and in some cases parameterizations (using a posteriori validation results). These uncertainties have statistically been compared to true errors against AERONET. This validation showed added value in the uncertainties (correlation to true error for different retrieval conditions), but absolute uncertainty values deviate from true errors in most cases – therefore using relative uncertainties (across regions, seasons) is recommended. Harmonization in absolute values of uncertainties is required and will be the focus of one task in phase 2 of Aerosol_cci (2014-2016).