Potential vorticity (PV) banners are low-level elongated PV anomalies that originate in close proximity to an orographic obstacle and define its wake. They have been proposed on theoretical grounds ...(Smith 1989) and have been a ubiquitous feature of high-resolution numerical simulations of flow past the Alps prior to the launch of the Mesoscale Alpine Programme (MAP) (Aebischer and Schaer 1998). Atmospheric wakes generated by simple obstacles have been the subject of several studies during 1990's, including observational studies e.g., Hawaii (Smith and Grubisic 1993), St. Vincent (Smith et al. 1997), Aleutians (Pan and Smith 1999), and a series of theoretical and idealized modeling studies (e.g., Schaer and Smith 1993a,b; Grubisic et al. 1995; Schaer and Durran 1997; Rotunno et al. 1999). However, MAP was the first field experiment in which the attempt was made to document PV banners in the lee of a complex obstacle such as the Alps. Specific objectives of the MAP PV banner project were related to the existence, structure, stability, and generation of Alpine PV banners.
The Mesoscale Alpine Programme (MAP) field phase took place in the fall of 1999 in the European Alps. Scientifically, the experiment focused on a number of objectives, as diverse as orographic ...precipitation, terrain-induced gravity wave breaking, orographycially-induced potential vorticity banners, gap flows, foehn life cycle, atmospheric boundary layer in mountaneous regions, potential vorticity streamers and hydrological processes. This contribution presents a summary of the observation-related advances that have been achieved as a result of MAP in our understanding of the above mentioned science.
Depuis l'expérience internationale pionnière GATE en 1974, notre documentation et notre compréhension du système de mousson africaine avaient évolué relativement lentement. Comment notre vision de ...cette mousson ressort-elle après les 10 ans du projet AMMA ? Si les principaux acteurs de ce système couplé atmosphère-océan continent étaient déjà bien connus, AMMA a permis d'approfondir le détail des processus en jeu et de leur couplage. D'une vision statique de ce système émerge petit à petit une vision plus dynamique où intervient désormais l'ensemble du globe : l'Afrique en entier, les latitudes tempérées, la mousson indienne et même toute la ceinture tropicale. Une voie est ainsi ouverte pour comprendre sa variabilité intra-saisonnière.
Since the pioneering GATE international field experiment in 1974, little progress had been made on the documentation and understanding of the West African Monsoon system. Ten years after the AMMA project was initiated, how has our knowledge of this monsoon evolved? Although the main actors of this atmosphere ocean-continent coupled system were already known, AMMA has allowed us to study thoroughly the details of the processes at play and their coupling. Starting from a static view of the system, a more dynamical view is now emerging, involving the whole Earth system : the whole African continent, mid-latitudes, the Indian monsoon and the entire tropical belt. This has opened new avenues of investigation into the intraseasonal variability of the West African monsoon.
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