应用气象学报 (Nov 2023)
Physical Inspection of Randomized Trial for the Artificial Rain Enhancement Experiment at Gutian from 2014 to 2022
Abstract
The verification of the effectiveness of artificial rain enhancement is a worldwide challenge. Based on random experiments of ground-based rocket artificial rain enhancement at Gutian from 2014 to 2022, physical verification of stage samples is carried out using radar macro parameters such as radar echo intensity, echo top height, and thickness of the negative temperature layer. The evolution characteristic analysis of dual-polarization parameters ZDR and KDP is conducted. The physical characteristic response of seeded cases is studied by combining ground raindrop size distribution data. The analysis results show that the non-seeded samples have a small increase in echo intensity, echo top height, and negative temperature layer thickness after hypothetical artificial precipitation enhancement operation, but then quickly decrease. Seeded samples generally show an increase in echo intensity after operation, reaching a peak after 36 minutes. There are 52.6%, 21.1% and 7.9% of seeded samples with maximum growth rates of 0-20%(excluding 0), 20%-50%(excluding 20%) and above 50%, respectively. Half of seeded samples show an increase in echo top height and negative temperature layer thickness, with the former showing a significant increase after 30 minutes and maintaining stability, while the latter increase significantly after 12 minutes. Among them, 36.8%, 13.2% and 2.6% of seeded samples increase with maximum growth rates of 0-20%(excluding 0), 20%-50%(excluding 20%) and over 50%, respectively. At the same time, the dual-polarization parameters ZDR and KDP show sustained enhancement after operation. From the physical response characteristics of seeded individual case, ZDR column appearing in the cloud after operation indicates that the upward airflow in the cloud has increased, causing the echo top height to rise and the echo intensity to increase or maintain. At the same time, KDP column also indicates that there are more large raindrops or partially melted ice particles in the cloud after operation. The ground rainfall size distribution shows a characteristic of increasing first with small and medium drops and then with large drops, resulting in an increase in spectral width. The maximum minute rainfall intensity generated by the cloud system within 50 minutes after the operation increases significantly, and the cumulative rainfall has increased by 49% compared to the operation time. In summary, cloud seeding helps the development, enhancement, and maintenance of clouds, not only increasing the number and size of precipitation particles, but also to some extent prolonging the life of the cloud.
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