High‐resolution numerical simulations of the convective system observed in the Lago Maggiore area on 17 September 1999 (MAP IOP 2a)

Abstract

SUMMARYDuring Intensive Observing Period (IOP) 2a of the Mesoscale Alpine Programme (MAP) a signi cant convective system developed in the Lago Maggiore area. Its evolution is simulated using the Meso-NH model run over three nested domains with a 2 km horizontal resolution for the nest grid. Model results are assessed by comparing computed precipitation and model radar re ectivities with observed parameters. A control simulation initialized with European Centre for Medium-Range Weather Forecasts analyses and run with the standard microphysical scheme of the model yields fairly realistic results. Neglecting the ice processes in the microphysical scheme degrades the numerical results, whereas, signi cant improvement is obtained when heavy rimed particles are considered to be hail instead of graupel.

Quantitative precipitation forecasting in the Alps: The advances achieved by the Mesoscale Alpine Programme

“…In the case of IOP 8 (a long-lasting episode of widespread stratiform rain), the various simulations carried out by Rotunno and Ferretti (2003, MM5), Lin et al (2005, MM5) or Asencio and Stein (2006, MESO-NH) have in common that they are less accurate than the IOP 2b simulations and overestimate precipitation, particularly over the Apennines. Regarding the other MAP events, some very encouraging results were obtained for the IOP 2a (Richard et al, 2003), IOP 3 (Asencio and Stein, 2006) 835 and IOP 5 (Pradier et al, 2002). All these three successfully simulated cases were associated with very narrow convective lines which cannot be resolved unless a very high resolution is used, as is evidenced by for instance Figure 14 of Pradier et al (2002).…”

“…The marked improvement in the MAPRA-based experiment was ascribed to a better representation of the conditionally unstable southerly flow over the Adriatic preceding the onset of the Bora wind and the subsequent strengthening of the low-level convergence over the area . Figure 4 presents results which were obtained with MESO-NH for the case of IOP 2a, a convective line that developed over the Alpine foothills and swept over the Lago Maggiore area (Richard et al, 2003). This event was not very intense in terms of accumulated precipitation (70 mm maximum), but was the most convective event observed during the whole SOP.…”

“…Finally, the MAP data were used to tune or improve the explicit microphysical schemes of some models. For example, Richard et al (2003) and Lascaux et al (2006) demonstrated that implementing a separate prognostic variable for hail (in addition to graupel) could be beneficial in cases of strong convection (IOP 2a).…”

Impact of North Atlantic evaporation hot spots on southern Alpine heavy precipitation events

“…Massacand et al, 1998;Fehlmann and Quadri, 2000;Richard et al, 2003;Argence et al, 2008;Ducrocq et al, 2008;Nussier et al, 2008;Schlemmer et al, 2010) considered events in autumn or early winter, when the Mediterranean is still relatively warm. This can cause considerable evaporation of moisture, which may be transported towards the Alpine ridge due to the flow induced by an upper-level PV streamer and contribute to the occurrence of such heavy precipitation events.…”

Long‐range transport of Saharan dust and its radiative impact on precipitation forecast: a case study during the Convective and Orographically‐induced Precipitation Study (COPS)

“…Complementary studies using microwave observations further assessed the cloud scheme (Wiedner et al, 2004;Meirold-Mautner et al, 2007;Chaboureau et al, 2008). Following the same approach, other instrument emulators were implemented into the Meso-NH system to simulate precipitation radar products (Richard et al, 2003;Caumont et al, 2006) and GPS zenithal delay (Brenot et al, 2006;Yan et al, 2009). The lidar simulator presented here is able to take account of the radiative impact of all the scattering particles predicted by the model, including cloud droplets, ice crystals, dust and other aerosol particles.…”