MANDOP analysis and airborne Doppler radar for mesoscale studies

The development, these last ten years, of airborne Doppler radars able to follow precipitating systems during a significant part of their lifetime and, more recently, of radars equipped with dual-beam antennas allowing the sampled area to be extended (avoiding the necessity of performing two consecutive flights over the same area in order to obtain the three-dimensional wind field), has increased the need for new wind-field analyses flexible enough to output wind fields at several scales of motion, in particular at mesoscale. Numerous retrieval techniques valid for ground-based radars exist. Some of them are devoted to convective-scale studies, others, such as the MANDOP analysis, are devoted to mesoscale meteorology. The application of these techniques to airborne Doppler-radar data is subject to new problems linked to the influence of the flight parameter's accuracy onto the sensitivity of the retrieved wind field (in particular the vertical-velocity field). The knowledge of the effect of this sensitivity is of crucial importance for mesoscale motions with very weak vertical velocities. In this context, the paper describes the application of the MANDOP analysis (a new analysis devoted to mesoscale meteorology and valid for any kind of Doppler-radar data but until now only tested for ground-based radar data) to the case of airborne dual-beam radar data, with special attention brought to the accuracy of the wind-field retrieval for mesoscale motions. The study of these problems, and of the expected accuracy on the retrieved wind fields, is performed by means of simulated data. An application of the method to real data extracted from the CaPE experiment data set is also made. This application is twofold. First, a comparison is made between fields retrieved from airborne radar data and several combinations of airborne and ground-based radar data, illustrating the flexibility of the analysis and validating its application at mesoscale on dual-beam radar data; then a comparison is made between MANDOP and an analysis devoted to convective-scale studies, the COPLANE analysis, on the same airborne data set, illustrating the capabilities of the MANDOP analysis to be applied within convective areas and thus to be used to scrutinize a precipitating system at various scales with the same airborne Doppler-radar data set.