Browsing by Author "Berne, A."
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Item Open Access Multifrequency radar observations collected in southern France during HyMeX-SOP1(American Meteorological Society, 2015-02) Bousquet, O.; Berne, A.; Delanoe, J.; Dufournet, Y.; Gourley, J. J.; Van-Baelen, J.; Augros, C.; Besson, L.; Boudevillain, B.; Caumont, O.; Defer, E.; Grazioli, J.; Jorgensen, D. J.; Kirstetter, P. E.; Ribaud, J.F.; Beck, J.; Delrieu, G.; Ducrocq, V.; Scipión, Danny; Schwarzenboeck, A.; Zwiebel, J.The radar network deployed in southern France during the first special observing period (SOP 1) of the Hydrological Cycle in the Mediterranean Experiment (HyMeX) was designed to precisely document the 3D structure of moist upstream flow impinging on complex terrain as a function of time, height, and along-barrier distance, and surface rainfall patterns associated with orographic precipitation events. This deployment represents one of the most ambitious field experiments yet, endeavoring to collect high-quality observations of thunderstorms and precipitation systems developing over and in the vicinity of a major mountain chain. Radar observations collected during HyMeX represent a valuable, and potentially unique, dataset that will be used to improve our knowledge of physical processes at play within coastal orographic heavy precipitating systems and to develop, and evaluate, novel radar-based products for research and operational activities. This article provides a concise description of this radar network and discusses innovative research ideas based upon preliminary analyses of radar observations collected during this field project with emphasis on the synergetic use of dual-polarimetric radar measurements collected at multiple frequencies.Item Open Access Orographic effects on snow deposition patterns in mountainous terrain(American Geophysical Union, 2014-01-07) Mott, R.; Scipión, Danny; Schneebeli, M.; Dawes, N.; Berne, A.; Lehning, M.Orographic lifting of air masses and other topographically modified flows induce cloud and precipitation formation at larger scales and preferential deposition of precipitation at smaller scales. In this study, we examine orographic effects on small‐scale snowfall patterns in Alpine terrain. A polarimetric X‐band radar was deployed in the area of Davos (Switzerland) to determine the spatial variability of precipitation. In order to relate measured precipitation fields to flow dynamics, we model flow fields with the atmospheric prediction model “Advanced Regional Prediction System.” Additionally, we compare radar reflectivity fields with snow accumulation at the surface as modeled by Alpine3D. We investigate the small‐scale precipitation dynamics for one heavy snowfall event in March 2011 at a high resolution of 75 m. The analysis of the vertical and horizontal distribution of radar reflectivity at horizontal polarization and differential reflectivity shows polarimetric signatures of orographic snowfall enhancement near the summit region. Increasing radar reflectivity at horizontal polarization over the windward slopes toward the crest and downwind decreasing reflectivity over the leeward slopes is observed. The temporal variation of the location of maximum concentration of snow particles is partly attributed to the effect of preferential deposition of snowfall: For situations with strong horizontal winds, the concentration maximum is shifted from the ridge crest toward the leeward slopes. Qualitatively, we discuss the relative role of cloud microphysics such as the seeder‐feeder mechanism versus atmospheric particle transport in generating the observed snow deposition at the ground.Item Open Access Seasonal small-scale spatial variability in alpine snowfall and snow accumulation(American Geophysical Union, 2013-02) Scipión, Danny; Mott, R.; Lehning, M.; Schneebeli, M.; Berne, A.In mountainous regions, snow accumulation on the ground is crucial for mountain hydrology and water resources. The present study investigates the link between the spatial variability in snowfall and in snow accumulation in the Swiss Alps. A mobile polarimetric X-band radar deployed in the area of Davos (Switzerland) collected valuable and continuous information on small-scale precipitation for the winter seasons of 2009/2010 and 2010/2011. Local measurements of snow accumulation were collected with airborne laser-scanning for the winters of 2007/2008 and 2008/2009. The spatial distribution of snow accumulation exhibits a strong interannual consistency that can be generalized over the winters in the area. This unique configuration makes the comparison of the variability in total snowfall amount estimated from radar and in snow accumulation possible over the diverse winter periods. As expected, the spatial variability, quantified by means of the variogram, is shown to be larger in snow accumulation than in snowfall. However, the variability of snowfall is also significant, especially over the mountain tops, leads to preferential deposition during snowfall and needs further investigation. The higher variability at the ground is mainly caused by snow transport.