• govern precipitation over major complex topography, and
• determine three-dimensional circulation patterns in the vicinity of large mountain ranges.

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.

Chapter 1: Motivation

• Operational weather forecasting with high-resolution numerical models has reached a stage where the Alpine circulations can be resolved adequately, and their effect on the key parameters such as precipitation has become directly amenable to numerical simulation.
• It has been realized that many, if not most, of the natural disasters in the Alpine region are linked to strong precipitation events -- landslides (e.g. Valtellina 1987), flash floods (e.g. Vaison-la-Romaine 1992, Brig 1993, Piedmont 1994), hail storms (e.g. Munich 1984) and large avalanches (e.g. Arlberg 1988). Improved prediction and earlier warning could significantly help to avoid loss of life and reduce damage. In general snow and rainfall are difficult quantities to forecast, especially if associated with deep convective activity and thunderstorms. Forecast failures in the Alpine region occur also as a result of the limited ability to simulate orographic circulations and their interaction with the synoptic-scale flows.
• Anthropogenic emission of greenhouse gases are expected to lead within the next century to a significant warming on the global scale. The assessment of the resulting impacts upon the Alpine environment is at a preliminary stage, in particular with regard to precipitation which is also crucial for fresh-water management in the neighbouring regions. Climatological studies and attempts to downscale global change scenarios to mountainous region will clearly benefit from a better understanding of the pertinent circulations and mesoscale processes.
• In addition, mountains are being recognized as one of the key factors which determine the geographical distribution of climate zones (see Fig. 2). Sound estimates regarding global change necessitate improved parameterization schemes for moujntain induced mesoscale processes.
• Airflow systems in mountainous regions create distinct planetary boundary layer features, and thus strongly influence environmental conditions, e.g., the level of air pollution.

The scientific problems pertinent to these issues are not only important in the Alpine region, but they are of general interest for many other mountainous regions of the earth.