Numerical simulations of a squall line observed during MAP IOP 2A

During the course of the MAP (Mesoscale Alpine Programme) field experiment, a major squall line developed in the afternoon of 17 September, 1999 over the Alpine foothills northwest of the Lago Maggiore and moved eastward during the night. This system has been quite well observed by the three ground based Doppler radars operating in the Lago Maggiore area during the MAP campaign.

Numerical simulations of this event have been carried out with a non hydrostatic model run over three nested domains of increasing resolution. The results of the high resolution simulation (2km) are quite consistent with the observations. The generation, propagation and life cycle of the system are well captured. The comparisons with the observations deal with rain gauges measurements, radar reflectivities, and radar derived wind fields.

Additional experiments show the sensitivity of results to the initial state (ECMWF analysis versus ARPEGE analysis) and to some parameters of the ice microphysical scheme.