MAP Newsletter 1

The scientific goals were clearly divided into two main classes of different but related interests, which partly is reflected in the new grouping. Gravity waves and associated topics were motivated by a strong scientific emphasis, wherein Foehn was featured as a concrete item of considerable concern to practical forecasting. Heavy precipitation (frontal and convective) combined with upper level features was presented as a more pragmatic issue closely related to the forecasting interests of several meteoro logical services in the Alpine region. Also, both topics are next door to climate issues, and additional pragmatism was expressed in that the matter of deep convection was felt to shower good funding. These lines of interest constituted the basis for the definition of the scientific key topics, a task that was achieved by day three to read

Orographically induced precipitation and convection
Orographically induced gravity waves and low-level flows
Validation of high-resolution mesoscale models over complex orography. Furthermore, a supporting objective has been agreed upon
Establishment of a climatology of mesoscale weather systems in the Alpine region

This last item shall include efforts to facilitate the collection and exchange of non-GTS data.

Strong links between these key topics and fronts, upper-level features and PBL were made, the latter being included as secondary topics of MAP . The presented synthesis reveals the scientific quality involved in addressing two issues of widespread interest.

Planning the Field Phase

The defined scientific objectives are linked to distinct and partly overlapping seasons. Given the non-feasibility of more than one special observing period, this led to the recommendation to have the field phase from mid August to mid-November 1998. This choice allows to capture deep convection and flooding in the southwestern Alps (which often takes place in September) and guarantees good probability of Foehn. Two target areas are required, one south of the Alps, possibly equipped with a surface meso-net which is particularly crucial for convection, and the other noth of the Alps for Foehn-related measurements. The availability of aircraft from the different contributing countries and institutions formed an important point of discussion. Much thought was given to topic-related strategies to warm up to the field experiment. The warm-up phase for key topic 1 would consist in an iterative process between high-resolution modelling and establishing of a profiler network for inter comparison, as well as for locating preferred regions of gravity wave breaking. The definition of the preferred location for deep convection is more troublesome, however, particularly since no perfect climatology is available for the southern Alpine area. To avoid conflicts between different objectives as far as airborne measurements are concerned, aircraft mission scenarios have to be developed as pedestal for on-line decision depending on specific weather situation.

MAP Newsletter. November 1994