Observation of precipitating systems over complex orography with meteorological Doppler radars: A feasibility study

This paper concerns the use of airborne or ground-based Doppler radars to o bserve precipitating systems over complex orography. As nearly all of the p revious experiments involving Doppler radars were conducted over flat surfa ces over the continents or the oceans, new techniques are needed firstly to separate ground clutter from meteorological signal and, in the case of air borne Doppler observations, to deduce navigational errors. Secondly, it is necessary to take the atmospheric circulation induced by orography into acc ount in the three-dimensional wind field analysis. Variational techniques a re presented to solve these problems. The proposed methods are tested with simulated groundbased and airborne Dop pler radar observations for analytic flows over analytic terrains and for n umerically simulated wind and reflectivity fields for the Brig event (22 Se ptember 1993) of heavy precipitation over the southern flank of the Alps (C osma and Richard, 1998), and with actual airborne Doppler data relative to weak snow showers over the Rocky Mountains on 12 March 1995.