|題名||人工增雨技術研發評估計畫(1/2) The development and evaluation of artificial rainfall enhancement techniques(1/2)
|英文摘要||To develop the abaility and technology with respect to rainfall
enhancement and then apply to domestic cloud seeding operation, this project was conducted to improve cloud seeding model and techniques with
air-platform, plan the application of semi-air-platform, develop local-produced seeding flares, and propose physical and chemical methods to evaluate the effect of cloud seeding.
Theoretical evaluation of the warm-cloud seeding effect with rain embryo
spray and condensation nuclei (CN) flares was perfomed using the Bowen
and detailed bin model, respectively. The Bowen model result indicated that a ten-thoudand times seeding effect may be obtained if the diameter of rain embryo is reduced to about 100 m, and mau reach even up to 100,000 times under favorable environmental conditions. As for seeding with giant condensation nuclei (GCCN)s, the optimal salt size is 4 to 8 m under a maritime aerosol environment, and from 8 to 10m under a continental aerosol environment. The GCCN seeding effect is more effective when the environment is more polluted as compared to the clean or oceanic backgrounds. These results are important bases for developing domestic warm cloud seeding flares.
The simulation result from regional weather model with detail
microphysics showed that, due to the presence of ample ice nuclei in the natural atmosphere, cold cloud seeding in Taiwan might reduce total precipitation, whereas using GCCN is less risky unless extremely high concentration of GCCN is used. In addition, conditions suitable for warm cloud seeding is much more frequent that that for cold-cloud seeding in Taiwan. We thus suggest using warm cloud seeding techniques as the main cloud seeding method in Taiwan.
As for the task of developing warm-cloud seeding flares, the recipie,
including chemical and mixture proportion, as well as the material sources have been identified. Ion composition analysis shows that the domestic flare that we made has similar compositons as the imported ICE flare, and is a potentially more efficient cloud seeding agent. Therefore, our domestic flares possibley can used to replace the ICE flares in the future.
We also proposed two solutions for spraying water droplets as rain
embryos using the C-130H platform. As for the AS365 helicopter, we have
produced finely grinded CaCl2 power and incorporated a powder-spraying
machine into a helicopter, whose function has been tested successfully in the Taichung airport. The B2N platform is evaluated and not suggested for future operation due to restrictions by ACC. From the experiment conducted offshore of Taitung, we demonstrated that the firework platform is a plausible platform for ground seeding operation.
A set of three methods are sesigned for qualitative evaluation of seeding effect: (1) physical ve rification with the polarizatic radar echo; verification using rainfall time series and spatial distribution, as the effect of ground flare seeding should emerge about 40 to 100 minutes after the release of seeding agent; (3) chemical verification by analyzing chemical composition in the rainwater, including the analysis of seeding material, and the food-dye that we added in the water spray of C-130H seeding. As for a more quantitative evaluation, we will need to rely on randomized seeding design and statistical
analysis, which will take a few years to accumulate enough date sample. All these evaluation methods should be used in cloud seeding operation the future.