A case study of the conditions for topographic cloud seeding based on the retrieval of satellite measurements

Taking the precipitation processes occurred in 21 June 2007 at Baiyu mountainous area in the northern Shaanxi as an example, the microphysical properties of clouds were retrieved by the satellite retrieval methodology. From the orbital satellite data of higher spatial resolution, the retrieved microphysical structures show that on the windward side of the mountain, the cloud top temperatures are about -31 ℃, and the effective radii of the particles are around 9 μm, with more supercooled water and little ice crystal contained, and that the low clouds whose temperatures are about -20 ℃ produce more precipitation due to the involvement of higher clouds above them in the rain process. The cloud area on the windward of the mountain which is about 4000 km2 brings about the good chance for the operational topographical cloud seeding. From the geostationary satellite data of higher temporal resolution， it is found, based on the three hour microphysical evolutions of clouds on the windward of the mountain, that the clouds had been maintaining rather deep, the effective radii of particles are stable, and no precipitation is triggered. Most cloud drops only experience the process transferred from diffusional growth to evaporation. All these suggest that the clouds on the windward of the mountain are the cloud system for the operational cloud seeding.