Premium
Small‐scale rainfall mechanisms for an idealized convective southerly flow over the Alps
Author(s) -
Gheusi François,
Stein Joel
Publication year - 2003
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.02.85
Subject(s) - geology , precipitation , convection , jet (fluid) , atmosphere (unit) , flow (mathematics) , climatology , scale (ratio) , atmospheric sciences , meteorology , geography , geometry , mechanics , physics , mathematics , cartography
Rain‐producing flows over the south side of the Alps are investigated with an idealized high‐resolution (2.5 km) numerical configuration where only three basic ingredients of typical heavy‐precipitation situations have been retained: (1) a uniform and stationary southerly flow far upstream from the Alps, which drives (2) a conditionally unstable atmosphere towards (3) the real topography of the Alps and the surrounding secondary mountains. Attention is given to small‐scale mechanisms of rainfall over the Po Plain and the Alpine slopes. These are linked with two orographically induced low‐level wind jets: the easterly barrier‐wind jet along the southern flank of the Alps and a south‐easterly jet formed over the sea along the south‐western flank of the Apennines and continuing over land up to the Alps. The specific role of the secondary relief upstream from the Alps in inducing or influencing these low‐level flow features, and also in triggering organized convection, is studied by means of experiments on the sensitivity to topography. The idealized configuration also allows the advantages of a convection‐resolving model for modelling precipitation distributions at the Alpine valley scale to be considered. Copyright © 2007 Royal Meteorological Society