The ultimate objective of the ESA Cloud_cci project is to provide long-term coherent cloud property data sets exploiting the synergic capabilities of different Earth observation missions allowing for improved accuracies and enhanced temporal and spatial sampling better than those provided by the single sources.
Figure 1 Examples of Cloud_cci cloud products. Left: Pixel-based (Level 2), middle: sampled on a global grid (Level 3U), right: averaged on a global grid (Level 3C)
The ESA Cloud_cci project seeks to utilize the increasing potential of the synergic capabilities of past, existing and upcoming European and US satellite missions in order to meet the increasing needs for coherent long-term cloud property datasets required by the scientific community.
The main objectives of this project are:
- Development and application of carefully calibrated and inter-calibrated radiance data sets – so called Fundamental Climate Data Records (FCDRs), for ESA and non ESA instruments in an international collaboration.
- Development of a coherent physical retrieval framework for the Global Climate Observing System (GCOS) cloud property Essential Climate Variables (ECVs), which is publicly available and usable by all interested scientists.
- Development of two multi-annual global data set families for the GCOS cloud property ECVs including uncertainty estimates based on FCDRs.
- Validation and inter-comparison of the multi-decadal cloud property products against ground based and other satellite based measurements taking into account the individual error structures of the individual observations as far as possible.
- Development of a cloud-simulator package to strengthen an application of Cloud_cci products for global and regional climate model analysis.
- Providing a common data base and the necessary assessment of cloud data sets as in the framework of Global Energy and Water Cycle Experiment (GEWEX).
- Development of a complete processing system distributed over Europe that can further strengthen operational production of cloud property data sets after the ESA CCI program is finished.
- Intensify the link with the climate modelling community.
Benefits for user community – Added value of ESA Cloud_cci products:
- Spectral consistency of derived parameters, which is achieved by an optimal estimation (OE) approach based on fitting a physically consistent cloud model to satellite observations simultaneously from the visible to the mid-infrared.
- Uncertainty characterization, which will be inferred by the application of the OE approach as physically consistent single pixel uncertainty estimation and further propagated to the final product.
- Increased temporal resolution by including multiple polar-orbiting satellite instruments, which also allows for mature cloud property histograms on 0.5° resolution due to high increased sampling rate.
- Comprehensive assessment and documentation of the retrieval schemes and the derived cloud property datasets including the exploitation of applicability for evaluation of climate models and reanalyses.
In Cloud_cci two global data set families for the GCOS cloud property ECVs including uncertainty estimates are generated:
- AVHRR-heritage dataset family covering all AVHRR, MODIS and (A)ATSR(-2) sensors onboard NOAA, MetOp and ENVISAT satellites. The algorithm developed and applied is CC4CL (Community Cloud Retrieval for Climate). The datasets of this family are named:
- Cloud_cci AVHRR-PM
- Cloud_cci AVHRR-AM
- Cloud_cci MODIS-Aqua
- Cloud_cci MODIS-Terra
- Cloud_cci ATSR2-AATSR
- ENVISAT synergistic dataset family based on simultaneous use of MERIS and AATSR measurements taken onboard the ENIVSAT satellite. The algorithm applied is FAME-C (Freie Universität Berlin AATSR MERIS Cloud). The synergistic dataset is named:
- Cloud_cci MERIS+AATSR
Figure 2 Overview of Cloud_cci datasets and the time periods they cover.