Kinematics and microphysics of MAP-IOP3 event from radar observations and Meso-NH simulations

This paper presents a kinematic and microphysical study of the MAP-IOP3 orographic precipitation event performed with radar observations and Meso-NH numerical simulations. Studies relying on both observations and mesoscale model simulations are of great interest for achieving a better understanding of intense precipitation events. Despite some slight discrepancies between radar observations and numerical outputs in the present work, both emphasize the same phenomena. The merging of two convective cells, which is an important mechanism to locally enhance precipitation is shown. Beyond Meso-NH outputs and radar observations similarities, the Meso-NH model completes and precises qualitative conclusions inferred from radar observations. In particular, it permits to identify and quantify the microphysical processes involved in the triggering and development of the orographic precipitation. The computation of hydrometeor mixing ratio and microphysical budgets highlights the convective nature of the IOP3 precipitation, which is characterized by efficient microphysical mechanisms such as heavy riming, warm coalescence, and melting of heavy particles (graupel and hail). More precisely, the initiation of the system is associated with warm microphysics whereas the development of the system and enhancement of rain involve graupel and hail.

Research Highlights
► Study of MAP-IOP3 event with radar observations and numerical simulations.
► Influence of Lago Maggiore area on orographic precipitation triggering.
► Local enhancement of precipitation by convective cells merging.
► Riming, warm coalescence and melting dominate IOP3 microphysics.
► Liquid and mixed microphysics intensification.