A novel approach for efficient rain enhancement through the combined glaciogenic and hygroscopic cloud seeding

Abstract. Rain enhancement by artificial cloud seeding is widely used to increase water resource in arid and semi-arid regions. However, large uncertainties regarding cloud seeding and its effectiveness remain. This study proposes a novel approach for efficient rain enhancement of convective clouds with warm cloud base by combining glaciogenic seeding with silver iodide (AgI) and hygroscopic seeding with cloud condensational nuclei (CCN). The numerical simulation experiments through the WRF model are systematically conducted and indicate that comparing to control (unseeded) experiment, the combination of an earlier hygroscopic CCN seeding in the low warm layers at a seeding rate of 10¹³ s⁻¹ and the subsequent glaciogenic AgI seeding in the upper mixed-phase layers at a seeding rate of 0.09 g s⁻¹ can increase the surface rainfall up to 57%, which is seven times higher than 7.97% in a single glaciogenic seeding and nearly three times higher than 20.74% in a single hygroscopic seeding, showing a much stronger rain enhancement rate in the new approach. It is found that the earlier hygroscopic seeding in warm cloud layers can greatly enhance the supercooled liquid water (SLW) content in cold cloud layers through updraft lifting and create a much more advantageous condition suitable for the subsequent glaciogenic cloud seeding. Moreover, the combined cloud seeding approach causes much stronger dynamic effect than any individual cloud seeding approach, and significantly enhances precipitation efficiency of convective clouds with warm cloud base. The novel cloud seeding approach has potential application in rain enhancement operation in middle and high latitudes.