MACC provides a large inter-related suite of products and undertakes corresponding product-development activities. For both efficient delivery and improvement of services and efficient management, the project is divided into components that either provide a specific sets of products or support the provision and evolution of these products. A broad division can be made between products at global and regional scales. The GLOBAL cluster comprises four components: G-GHG, G-RG, G-AER and G-IDAS. The first three are devoted to aspects of observations, modelling, product validation, flux inversion and product generation that are specifically related respectively to greenhouse gases, reactive gases and aerosols. G-IDAS develops the global data assimilation for all three types of atmospheric constituent, runs an integrated global production and product delivery system, and provides associated meteorological and climatological information derived from ECMWF’s meteorological operations and climate reanalysis. G-IDAS relies on G-GHG, G-RG and G-AER for much of what it needs to improve its global data assimilation, and delivers products not only to other MACC clusters, downstream service providers and other users, but also to G-GHG, G-RG and G-AER for further processing. The global cluster as a whole receives observational data on constituents from D-SAT and D-INSITU and data on emissions from D-EMIS and D-FIRE. It builds both on the comprehensive analysis and forecasting system and related components developed within the GEMS project and on specific services developed within the PROMOTE project.
The interactions between the components of the GLOBAL cluster, the other components and clusters of MACC and external inputs and outputs are illustrated below. Arrows show the main flows of data, products, software and other project information. In addition, specifications of user requirements and feedback on data and product quality flow from the downstream service providers and end users to the GLOBAL cluster, and from the GLOBAL cluster through the D-SAT and D-INSITU components to the providers of observational data.
The cluster of global components
There is a high level of scientific integration within G-IDAS. For example, the assimilation of data on reactive gases provides improved knowledge of some aerosol precursors while the assimilation of data on aerosols improves the simulation of heterogeneous chemistry. The reactive-gas assimilation in addition provides information needed to evaluate the sources and sinks of greenhouse gases that result from oxidation. There is also a high level of technical integration within G-IDAS, with all components installed in as unified a way as possible within the Integrated Forecasting System software used by ECMWF for its operational weather prediction.
Beyond this, connections among the global components (and related cross-cutting components) occur in the forms of data flows and transfers of improved algorithms and inputs. For example, at the level of data, the four-dimensional fields of aerosols and greenhouse gases produced by G-IDAS, which are products in their own right, are also delivered to G-AER and G-GHG as inputs for the generation of improved estimates of surface fluxes. Similarly, the inventories compiled and evaluated by D-EMIS are passed to the global components for use in the assimilation and flux inversion algorithms. At the level of exchange of algorithms, the service-evolution tasks within the global components feed improvements into the global assimilation system. There are also important feedbacks from the global components to improve their inputs. For example, statistics on the changes made to surface fluxes of the greenhouse gases by the assimilation and inversion procedures can be used to guide improvements to the inventories used to estimate these fluxes in the first place, thus providing a link between G-GHG and D-EMIS.