Mountains, and in particular Alpine-type orography, instigate or influence a rich range of mesoscale phenomena. These phenomena and their associated processes are intricate in character, interact with larger and smaller scale flow, and are responsible for much of day-to-day mountain weather and for many of the extreme weather events. Moreover their composite effect contributes significantly to determining the climatic features of mountainous regions.
These facets of orographic-related mesoscale phenomena combine to make their adequate observation, basic understanding, and successful prediction both difficult and desirable enterprises. The challenge has been highlighted by various developments in the last decade: pertinent field studies helped establish the importance of orographic effects and pinpointed gaps in our information and knowledge base; new high resolution numerical models revealed various deficiencies (e.g. the representation of meso-scale moist processes and orographic effects), the lack of suitable observational data for the inter-related purposes of diagnostic analyses and the initialization and validation of forecasts; and the emergence of novel observing systems (e.g. profilers, light-weight dropsondes, airborne Doppler radar and lidar) can contribute substantially to remedying the shortcomings.
The Mesoscale Alpine Programme (MAP) is a measured response of the international atmospheric and hydrologic scientific community to the foregoing challenges and developments. It is conceived as a coordinated and integrated programme of basic research that has direct practical applications in the realm of numerical weather prediction and river runoff forecasting. The programme's coupled overall aims is to further our basic understanding and forecasting capabilities of the physical and dynamical processes that
One of the two core MAP topics relates to the study of orographically-influenced events of deep convection and frontal precipitation to ascertain their scale-interaction, internal structure and microphysical characteristics. Intimately linked to these atmospheric processes is the hydrological response of Alpine watersheds. The second relates to the consideration of the phenomena and processes that give rise to Alpine drag effects with particular regard to the role of three-dimensionality, transience, the boundary layer, cloud processes and the Coriolis effect. These core activities will be supported and complemented by related climatological and dynamical studies linked to Alpine aspects of climate and stratosphere-troposphere exchange.
The MAP is designed as a multi-year programme structured in three phases - an extended ~3 year preparatory period, a 13-month field phase including a shorter intensive special observing period of 3 months, followed by an evaluation period. In Phase I activity will centre on: the climatology of Alpine mesoscale weather systems, numerical experimentation and the detailed systematic evaluation of the performance of current forecast models, the testing of new observing systems. This information base will serve to refine scientific hypotheses on the pertinent phenomena and processes. It will concomitantly help to fine-tune the design and observational strategy for the field experiments of Phase II, which will be undertaken with a state-of-the-art range of instrumentation, and will involve the acquisition of specific and detailed data sets. Integral feature of Phase III will be the assembly and analysis of the observational field data, the testing of hypotheses, and the application of the results in the context of operational forecast models.
Central to the establishment of MAP has been the identification and dovetailing of fundamental research issues and practical forecasting needs. It is this combination that has guided the programme's design, will stimulate its execution, and aid the incorporation of the accrued knowledge into the operational forecasting environment. The MAP is geared to the successful completion of this process and thereby to benefiting the public at large.
