Response of Cloud and Precipitation Properties to Seeding at a Supercooled Cloud‐Top Layer

Abstract

Abstract To accurately identify ideal operating conditions for scientific cloud seeding and to collect evidence of the effects of seeding, a set of three flights, with figure‐8‐like paths, was designed for supercooled liquid water detection. These flights were conducted near the cloud top before seeding, during seeding, and upon re‐entry. Using both in situ aircraft and satellite remote sensing observations, a comprehensive analysis was conducted to understand the response of cloud properties to seeding within supercooled cloud tops. Satellite observations showed clear icing cloud tracks after seeding with abundant supercooled liquid water near the cloud top. Radar observations confirmed enhanced radar reflectivity echoes in cloud‐seeding regions. For regions cloud seeded with supercooled liquid water, the liquid droplets quickly froze into ice crystals, which further grew into large ice crystals via vapor deposition, riming, and collision‐coalescence processes. With these processes, large ice crystals formed and rapidly fell downward, causing the sinking of cloud tops and precipitation to fall to the ground. By contrast, there were no such phenomena in the regions without supercooled liquid water or in those regions with supercooled liquid, but otherwise without seeding. In addition, radar reflectivity echoes quickly decreased in all regions without seeding. The evolutionary characteristics of radar echoes and in situ observed cloud and precipitation properties suggest that the response of cloud microphysical characteristics to seeding varies with time and location due to various seeding potentials, leading to different formation conditions of both cloud‐top icing and cloud tracks.

Keywords

• supercooled liquid water
• cloud seeding
• icing cloud track
• cloud microphysical properties