Comparative study of liquid carbon dioxide and silver iodide seeding effects on cumulonimbus clouds rainfall enhancement and hail suppression

Abstract

In this work, a comparative study of liquid carbon dioxide versus silver iodide seeding effects on a one-dimensional transient cumulonimbus cloud model is made. The over-riding concern is to figure out the implications of different seeding methods and agents for rainfall enhancement and hail suppression in cumulonimbus clouds. Based on the model results, it may be inferred that for the liquid carbon dioxide seeding, the seedability temperature limit is wider and the dynamic effects and precipitations are stronger compared to those of the silver iodide seeding. In addition, based on the model results, the rainfall enhancement can augment to 52 % for liquid carbon dioxide as the cloud top level increases. However, this rainfall enhancement can augment to only 19 % in the case of silver iodide seeding. Also, the model results show that for clouds with cloud top level less than 7 km, the cumulative rainfall for the point seeding is less than that for the horizontal seeding, but for clouds with cloud top level more than 9 km, the rainfall amount for the point seeding is more than that for the horizontal seeding. The results also show that there exist two threshold temperatures for the silver iodide seeding methods. The model results also indicate that the silver iodide seeding in the mixed clouds can be used for the cloud seeding with the aim of hail suppression. In general, the obtained results from this model show to be comparable with the recorded data at rain gauge stations.