Cyclones and mesoscale convective systems (MCSs) often cause high-impact weather (HIW) in the western Mediterranean. However, it is still a great challenge to predict where and under which conditions these systems lead to HIW. While the synoptic conditions of these events are relatively well known, the processes and mechanisms governing the precise location of the systems are often unclear. The complexity of orography, land use, and soil texture as well as the difficulty to characterize the initial state of soil moisture and atmospheric variables with high spatial resolution are some reasons why HIW is hard to predict. To improve the understanding of the Mediterranean hydrological cycle, the HyMeX (Hydrological cycle in the Mediterranean Experiment) project was initiated. Within the HyMeX measurement network, the Karlsruhe Observatory for Convection Studies (KITcube) is regarded an important component. As KITcube will be installed in one of the key regions (Corsica/Ligurian Sea) relevant to the evolution of HIW, IMK aims (i) at monitoring the conditions in the pre-convective environment of HIW, (ii) at quantifying the contribution of the different processes leading to HIW, and (iii) at investigating the influence (orographic, thermal, aerodynamic) of the Corsican Island on the initiation and evolution of single cumulonimbus (Cbs), MCSs, and Cbs which are embedded in cyclones.
Figure 1: Orography of the western Mediterranean region (left) and of the Corsica island (right)
To improve our experimental capability of understanding convection initiation and modification, the new observing system KITcube was developed by IMK. The system is designed to monitor the evolution of convection in its different stages (from initiation of convection, cloud formation to growth into deep convection with precipitation) within a box of about 10 x 10 x 10 km3. The whole system is mobile and allows for flexible scan strategies with its different remote sensing systems. The KITcube consists of a surface-based network with stations measuring the standard meteorological parameters of temperature, humidity, air pressure, wind speed and direction (4 mobile stations), turbulent fluxes (7 stations for sensible heat and momentum flux measurements, 1 scintillometer) and the energy balance at the Earth’s surface (2 stations measuring the components of the radiation and surface energy balance as well as soil moisture and soil temperature profiles). These stations normally are distributed over the whole area of KITcube to account for surface inhomogeneities and terrain height.
The KITcube includes two scanning Doppler wind lidars and a third wind lidar for the lowest 500 m to measure wind speed and direction with high temporal and spatial resolution (Fig. 2). A sodar is available for mean wind profile observations. A micro-wave radiometer (HATPRO) measures temperature and humidity profiles as well as the integrated water vapor content. Two infrared-radiometers incorporated in the micro-wave radiometer system estimate the cloud base and two cloud cameras deliver information about the distribution and evolution of clouds in the surroundings of the wind lidars. A scanning cloud radar is installed to monitor the development of clouds and to estimate the horizontal wind profile in clouds. A vertical pointing K-band rain radar, X-band rain radar, disdrometers, and a ceilometer supply additional information about precipitation and cloud base. Two radiosonde systems can be operated at different sites to provide temperature, humidity, and wind profiles in intervals of hours.
Newly developed dropsondes are available to measure in key regions for the evolution of convection. These sondes can be dropped from the DO 128 research aircraft operated by the Institute of Flight Guidance and Control of the Technical University of Braunschweig. The DO 128 is additionally equipped with instruments to measure the standard meteorological parameters, turbulent fluxes of sensible and latent heat as well as the components of the net radiation. The aircraft can be operated very closely to the sea surface (approximately 30 m) to measure the turbulent fluxes of sensible and latent heat.
|Figure 2: Profiling systems included in KITcube|