Publication Date:
2015-09-27
Description:
The first Special Observation Period of the HyMeX campaign took place during Fall 2012. A specific observational network has been set-up in The South of France with the aim to better understand the role and impact of a complex terrain on the horizontal and vertical structure of rainfall and the associated microphysical processes. The event, referred as IOP7a, that occurred on the 26 th of September 2012, is studied in this paper. A first analysis, based on two reference parameters of the drop size distribution (DSD), shows that the topography of the region has an impact on the rainfall structure at a fine scale and that rainfall regimes also has an influence on the DSD parameters. A more detailed study, based on the evolution of the shape of the DSD and the evolution of the liquid water content (LWC) with respect to different rainfall regimes, reveals that the coalescence mechanism is of significant importance for the different rainfall regimes and for the different topographic areas. Nonetheless, as we get closer to the ground, the modification of the DSD shows that other microphysical and dynamical processes such as evaporation, break-up, turbulence in the presence of vertical wind, might compete with the coalescence mechanism or enhance it. The respective strengths of these processes depend on the local environment; the coalescence seems enhanced by a layer with higher LWC as the local terrain becomes more complex and evaporation appears more important above flatter terrain. Thus, both the orography and the rainfall regime can impact the rainfall structure and the associated microphysical and dynamical processes.
Print ISSN:
0035-9009
Electronic ISSN:
1477-870X
Topics:
Geography
,
Physics
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