I figured I should just dig up an old thread and update it instead of posting a new topic
http://www.laramieboomerang.com/articles/2014/12/23/news/doc549902a087411614030872.txt
Wyoming cloud seeding project shows promising results
BY TIM STEERE /
TIMS@LARAMIEBOOMERANG.COM • TUESDAY, DECEMBER 23, 2014
The next time you see that ominous winter storm cloud looming over the horizon, fear not, for that cloud might not be your ordinary frozen mass of crystallized water drops.
Based on the results of a nine-year state-sponsored $13 million study, cloud seeding, which refers to the release of silver iodide into clouds via a generator, has a 5- to 15-percent positive effect on wintertime snow accumulation in the Sierra Madre and Medicine Bow mountains, ultimately resulting in a 1.5-to 5-percent increase in overall snowpack. Silver iodide is a catalyst of sorts for ice crystal formation in clouds.
However, UW researchers involved in the Weather Modification Pilot Program are reluctant to make any claims placing absolute confidence in the findings because of several manipulations of ambiguous data conducted by scientists and statisticians at the National Center for Atmospheric Research, or NCAR.
“Personnel at NCAR devoted a significant amount of time looking at the precipitation records with no knowledge of what was seeded,” said Terry Deshler, a retired UW professor of atmospheric science and member of the project’s Technical Advisory Committee. “They treated it all the same and eliminated certain cases because of no precipitation data available. They ended up with 118 experimental cases, but the significance was .28, which means there’s a 28-percent chance the increased precipitation results could have happened purely by chance.”
However, when researchers considered the possibility of upwind precipitation contamination, they found there were 20-30 cases where precipitation was likely the result of wind bringing it elsewhere.
“When you ruled out 20-30 cases where contamination was likely, you find that there was a much higher chance of increased precipitation,” Deshler said. “Although we can’t say it with any statistical confidence, they still believe the way they manipulated the data makes some statistical sense, and concluded there was a 5- to 15-percent chance of precipitation increase from seeding.”
In arid states such as Wyoming, cloud seeding has the potential to benefit a variety of parties, as higher precipitation amounts could be used for more than just public drinking water use.
“For agriculture and much of Wyoming in the western part of the state, water is a highly priced commodity,” said Bart Geerts, a UW professor of atmospheric science who has also studied cloud seeding in separate instances. “The basic reason why all this is being done is to increase the snowpack and get more water in the streams.”
Though silver iodide is not a naturally occurring substance in normal weather cycles, the compound has little, if any known effects on the environment once released into clouds.
“The silver measured in the stream flows after the melt has not substantially increased and the variations in silver concentrations are due more to the geology of the bedrock,” Geerts said.
Additionally, only certain kinds of clouds are “seedable.” For seeding to have any noticeable effect, temperatures must be colder than 17 degrees Fahrenheit, wind must be moving in a favorable direction and super-cooled liquid water must be present, conditions which only exist about 30 percent of the time, Deshler said.
“Thirty percent of the time, those conditions were met over eight winters,” he said. “Only about half the time during that 30 percent there was actually precipitation happening.”
Still, the future looks promising for cloud seeding efforts, especially for states in the lower Colorado basin.
“If you go to California or Arizona, now cloud seeding seems to be a good deal,” Deshler said. “Water conservation districts have the capabilities to do that, but for a larger operation like was done here, you need to have the state involved.”
