A holistic view of precipitation systems from macro- and microscopic perspective

Polarimetric radars are now widely used for precipitation observations in weather and climate research since they offer significant information for the improvement for atmospheric models and numerical weather prediction. Both macrophysical and microphysical processes related to precipitation initiation and processing can be inferred by dedicated scan strategies. In the frame of the initiative for High Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)2), which focuses on improving the accuracy of climate models in relation to cloud and precipitation processes, the HD(CP)2 Observational Prototype Experiment (HOPE) was designed to provide a critical model evaluation at scales covered by Large Eddy Simulation (LES) models, which in turn will be used to better understand sub-grid variability and microphysical properties and processes parametrized by larger scale models. HOPE took place during April and May, 2013, in the vicinity of the TR32/JOYCE (Transregional Collaborative Research Center 32/Jülich ObservatorY for Cloud Evolution) observatory, where a cube of approximately 10 x 10 km was continuously monitored by three K-Band cloud radars, several wind, aerosol, temperature and water vapor lidars, frequent radiosonde ascents, several sets of dual all-sky cameras for stereoscopic cloud reconstructions, and a dense radiation sensing network. Three X-band polarimetric radars installed in Bonn (BoXPol) and the vicinity of JOYCE (JuXPol and KiXpol), were operated in order to obtain together with the other instruments a holistic view of precipitation systems from covering both macro- and microscopic processes. The area is additionally covered by three C-Band precipitation radars of the German Weather Service (DWD), part of which have also polarization diversity. An object-based approach, which identifies a set of radar and satellite-derived descriptors characterizing the structure and temporal development of precipitation systems quantifies the macroscopic scale. Examples are the height, intensity and temporal change of the brightband, size and evolution of columns of enhanced differential reflectivity (ZDR), and the cloud top temperatures and heights. All identifiers can be considered as proxies of precipitation generation and evolution, and they relate to the precipitation yield by the system. The polarimetric moments and their evolution within an detected object allow for a detailed insight into the evolution of droplet size distributions (DSDs) and the associated microphysical processes like coalescence, breakup, freezing, etc. We will show results from the exploitation of the extremely sensor synergy potential during HOPE ranging from frontal passages monitored by cross-frontal high-frequency RHI (range-height indicator) scanning to the temporal evolution of three-dimensional composites of whole convective systems derived from the superposition of the different observations.