2.3 The GEMS Strategy to Advance the State of the Art

There has been extensive discussion in the international community on the way forward in studies of atmospheric omposition and dynamics, leading to the publication in the last two years of key reference documents including

• the GCOS second adequacy report (2003),

• the forthcoming report of  the IGOS_P Theme on Atmospheric  Chemistry (IGACO, 2004),
• the report of the IGOS_P Carbon Theme (2003),
• the first report of the Global Carbon Programme (2003).

These documents contain broadly-based and peer-reviewed statements of the consensus of the international community on the way forward. The GEMS strategy implements key recommendations from  these reports on data assimilation and forecasting. The strategy proposed here therefore has excellent prospects for meeting its users’ needs.

Figure 1.2 illustrates the main strands of the GEMS strategy to build an integrated operational system for monitoring and forecasting the atmospheric chemistry environment:  Global Reactive Gases (GRG), Greenhouse Gases (GHG), Global Aerosol (AER), Regional Air Quality (RAQ), and the GEMS global atmospheric assimilation system at ECMWF. The building blocks of the separate elements of the system already exist. The schematic also illustrates the scientific interactions between the strands of development, which will develop and mature as the integration of the system proceeds.

-->

Figure 1.2: Schematic illustrating the linksand the flow ofdata and  information  between the main elements of the GEMS system: Greenhouse Gases (GHG), Global Reactive Gases (GRG), Global Aerosol (AER), Regional Air Quality (RAQ) and the global atmospheric assimilation system at ECMWF.

In formulating the strategy, both scientific and practical considerations were taken into account. The primary scientific goal is to create an architecture which will provide a fully integrated treatment of all aspects of atmospheric composition and dynamics when it becomes operational towards the end of 2008. Practical considerations shaping the strategy include the need to

·        achieve a fully integrated system built on existing capabilities,

·        achieve operational robustness and resilience,

·        implement a well-tested integrated system which has the flexibility to exploit and support new scientific developments.

The strategy is based on a step-wise approach to establish in parallel, and validate, individual elements of the system in the first half of the period, and then to merge the individual components in an integrated system, and validate the integrated system.

The GEMS system will be built by leading European science teams and a leading European implementation team. The GEMS operational system is without precedent, and without equal, in a number of key respects.

The science on which the system will be built will be state-of the art, and there will be a clearly articulated method to incorporate and exploit new scientific findings.

The operational system for greenhouse gases and for the inference of surface fluxes will be the first such operational system. It will considerably strengthen the already strong European position in international negotiations, because of its transparency and sophistication.

Research systems for assimilation of reactive gases and aerosol have been developed in recent years, but none has the comprehensive use of satellite data, the comprehensive validation mechanisms and the high spatial resolution of the system proposed here. Again the operational global system will be a first, and will maintain and strengthen European leadership in these areas

The GEMS assessments of the impact of the global composition changes on regional air quality will be based on  a range of regional air-quality models using similar assessment protocols, so the assessments will be remarkably comprehensive and extensive, examining impacts on mean fields and on extreme events.

The operational GEMS system will therefore provide a major improvement in European capabilities to forecast natural disasters, to monitor the global environment, and to advance the science of atmospheric dynamics and composition.