Comparison of Model-Predicted Transport and Diffusion of Seeding Material with NOAA Satellite-Observed Seeding Track in Supercooled Layer Clouds

Abstract

From 0615 to 0749 UTC 14 March 2000, an operation of cloud seeding for precipitation enhancement by aircraft was carried out in the middle part of Shaanxi Province, China. National Oceanic and Atmospheric Administration (NOAA)-14 satellite imagery was received at 0735 UTC for the study region. A vivid cloud track appeared on the satellite imagery; its length was about 350 km, and its average width and width maximum were 9 and 14 km, respectively. Through application of a three-dimensional numerical model of the transport and diffusion of the seeding material, the simulated plume shape, the turning points, and the width and length of seeding lines agree with that of the cloud pattern indicated by the satellite imagery. The track is consistent with the transport and diffusion of the seeding line. All of these factors suggest that the cloud track that is detected by satellite imaging is the direct physical evidence of cloud seeding near the cloud top, with the cloud responding to the transport and diffusion of the seeding material and/or the propagation of the glaciation by secondary effects. The track is indeed caused by the cloud seeding, and the model can predict the evolution of the response zone of cloud seeding. For this seeding case, the duration for segments of the seeding line varies between 20 and 80 min, and the time period for each segment of the seeding line diffusing to the maximum width is about from 40 to 70 min. One hour after cloud seeding, the dispersion rate of the cloud track is 7.0 km h?1, and the predicted expansion rates of the seeding material concentrations of 1 and 4 L?1 are 7.6 and 4.6 km h?1, respectively. The comparison demonstrates that the numerical model of transport and diffusion can predict the main characteristics of transport and diffusion of the seeding effect, and the simulation results are reasonable.