The western Mediterranean as a sensitive region for cyclone formation causing heavy-rain events and long-range dust transport

1. Subjects and Participants 1.1 Subjects Convective, mesoscale and synoptic-scale weather systems in the troposphere are responsible for the damaging impacts due to wind, heavy precipitation and flooding and also a crucial role in the transport of moisture, trace gases and aerosol. A significant part of the human impact of climate change is experienced through changes in tropospheric systems. Important examples of such systems are cyclones developing over the western Mediterranean Sea and associated large amplitude upper-level troughs that extend southwards enforcing transport between the mid latitudes and the sub tropics. Such phenomena are neither easy to analyse nor to predict and there are many factors associated with their development, evolution, and predictability that are incompletely researched and poorly understood. Consequences are imprecise forecasts which might lead to economic as well as ecologic losses in the area affected by such weather and climate. The Mediterranean cyclones are often leading to enforced vertical moisture transport and mesoscale lifting accompanied with embedded convection and subsequent heavy precipitation. In some cases flash floods south of the Alps occur (Buzzi and Foschini, 2000). The associated upper tropospheric troughs may cause air pollution events over the Mediterranean Sea by transport of mineral dust from northern Africa over the Mediterranean Sea to Europe (Levin et al. 2005). Finally tropical cyclones pose a substantial threat to life and property in the tropics and mid latitudes due to their strong winds and heavy rainfall with associated high seas, storm surge and severe flooding (Jones et al. 2003). The scale of the systems to be investigated ranges from mesoscale γ (convection, embedded convection, squall lines) to the synoptic scale (MCCs, Mediterranean depression, tropical cyclones). The scientific goal is to use a combined observational and modelling strategy to elucidate the essential dynamical mechanisms that limit the quality of the numerical weather prediction of such systems, especially the precise prediction of the heavy precipitation and storm events in space and time and that determine the transport of air pollutants by those circulation systems. As the cyclones and convective systems cover a wide range from local catchment scale to European scale as well as forecast times from nowcasting to medium- range, process studies measuring the decisive parameters have to be made on equivalent scales. Therefore the use of a long range and high altitude research aircraft is necessary. Better understanding of the governing flow patterns and their appropriate prediction give reason to reduce the damages and air pollution risks associated with the processes mentioned and therefore might be beneficial in ecological and economical aspects.