Effects of cloud seeding in west Texas

Analysis of three-dimensional, volume-scan, C-band radar data using sophisticated tracking software indicates that AgI seeding increased the areas, durations and rain volumes of the cells. The radar-estimated rainfall volume at bases of the Agl-treated cells was more than double the rain volume from the cells that received simulated treatment. This result is significant at the 3% significance level using rerandomization procedures. In moving from the cell scale to the larger scales, it was found that cell merger occurred twice as often in the AgI-treated cases. The next step focused on the areas in which the cells received treatment. This "focused area' approach involved calculations for radii of 5, 7, 10, 15, 20, 25 and 35 km around each treatment position, providing eight separate analyses. The rainfalls from the seeded cells exceeded the rainfalls from the non-seeded cells in the focused area by over 50% by the end of the analysis period. Because of the small sample and the large natural rainfall variability, it is likely that chance has confounded this assessment of the results of treatment in the SWCP. -from Authors