High-resolution weather forecast for an alerting system in the Alps area

A project called SISTEMA, co-funded by Regione Lombardia (the most important region in Italy), has been started at the end of 2008. The aim is to develop an alerting system for extreme events, depending on meteorological conditions, linked to hydro-geological events (for example debris flows) or atmospheric emissions due to an accident in the potential-risk plants. The final aim is to have a system able to forecast any potential risk over the selected areas or in that sub-areas where their characteristics make them very sensible to meteorological and local conditions. Moreover, it is also considered the management of the potential risk, defining the potential risk for all relevant scenery, for each of them operational procedures have been established to mitigate risks and the effects of potential disasters depending on the meteorological and hydrological event as well as the accidental atmospheric releases of dangerous pollutants. A special focus has been made on around Tirano, Valtellina, an area in the Alps near Switzerland boundary and Bernina region. Meteorological simulations are made over a mesoscale domain centered on Lombardia, which includes the central Alps region, its sub-alpine area and the Po valley. Operational forecasts are planned to be made up to 48-96 hours, depending on the domain and the resolution. The selected model is the WRF, which is currently used at Epson Meteo Center at different scales and resolution. Multiple-nesting have been used to simulate meteorological fields over the final mesoscale domain, starting from a larger domain centered on Italy which is included in a continental-scale domain over Europe and surrounding areas. The final mesoscale domain has an horizontal resolution of 1.33 km, while the Italian domain has an horizontal grid mesh at 4km and at the European scale domain the horizontal resolution is 12 km. The same modeling chain has been also used to reconstruct 57 past situations in connection with extreme events relevant to hydro-geology (debris flow, floods). These case studies cover a time period ranging from 1951 and 2009. Other simulations have been made for relevant cases after 2000. Initial data from all cases before 1999 have been taken by NCEP/NCAR reanalysis, while after that date the data comes from AVN-GFS initialization. Data from the Mount Lema radar by the Swiss Meteorological Institute have being used for comparison and calibration purposes. Particularly, 3-hours accumulated radar precipitations can be used for calibration and these data have been available to us from 2005. Before that data, only 24 hours accumulated value have been available; due to the fairly time and range coarse data, these ones cannot be used for quantitative purposes and they have been considered only for a qualitative comparison. Results of the performed simulations have shown that the model can reproduce quite well the considered events, both from the rightness of the highest-value locations of the precipitation and its distribution, as well as the timing of the examined events. The first comparison with the radar data have also shown that some systematic over-estimations may appear when the rain intensity is greater than 20 mm/3h). Some precipitations, but with generally low values, also occur in mountain areas where radar data don't show any echoes. However, the simulations performed in the relevant cases, when an the extreme hydro-geological event occurred, have shown quite correct precipitation values which in turn can be used as the input in the hydrological models. These ones are able to correctly identify the threshold values for that event and the possible overcoming. In this case, the alert procedure will start, sending information to local authorities and decision makers and activating any required mitigation of risks and effects.