Developments in Diagnostics Research

Over the years, data assimilation and forecast schemes have evolved into very complex systems. For example, the ECMWF data assimilation system now handles a ve ry large range of space and surfacebased meteorological observations, combining these with p rior information of the atmospheric state and using a comprehensive linearised forecast model to ensu r that the observations are incorporated in a dynamically consistent way. Meanwhile the ECMWF f orecast model itself represents ever more physical processes, with ever increasing complexity, and is integrated at ever higher resolution. Recognising that any analysis or forecast is actually a probabilistic one, ECMWF continues to incorporate representations of uncertainty into all its fo recast components. Efficient and coordinated diagnosis of such a complex system is a necessity. Diagnostics has always been an active area of research and de velopment at ECMWF. Presently, ECMWF has a small nucleus of scientists dedicated to diagnos tics, who have a broad understanding of the global circulation and an overview of the assimilatio n and forecasting systems. Their unifying role will become ever more important as progress leads, i nevitably, to more fragmentation and specialisation within the overall task of producing foreca sts. However diagnostic work is not only about getting an overview, because all researchers need to p roduce ever more detailed diagnostics within their own particular fields. These trends raise the qu stion of whether we will need to enhance communication, coordination and collaboration across the traditional section boundaries in future. In order to address this issue, and to produce this report, a ‘ Working Group on Diagnostics’ (WGD) has been established at ECMWF. In this report, a diagnostics framework is introduced which highlights key diagnosis areas and their links. From each area, one or two ‘strategic’ diagnostic too ls ( r techniques) are highlighted. These tools are ‘strategic’ in that they are likely to be developed further and will inform future system developments. In order to demonstrate the utility of across -section collaborative work, these tools have been used to collectively address a long-standing prob lem for the ECMWF forecasting systems: that of the over-active Asian monsoon. This case-study prov ides a structural blue-print for future across-section projects focused on other forecasting prob lems and on the assessment of new model cycles. In discussing the above, together with future diagnostic re quir ments, this paper shows where ECMWF stands at present in terms of diagnostic work and proposes a s trategy that will ensure it meets the challenges of the future. Technical Memorandum No. 637 1 Developments in Diagnostics Research