Food for fertile debate: cloud seeding is back |

Food for fertile debate: cloud seeding is back

Bob Berwyn

Whether Mother Nature is in the mood or not, Durango weather wizard Larry Hjermstad is firing up his cloud-seeding generators all the same.Hjermstad, manager of Western Weather Consultants LLC, recently signed a contract with the Denver Water Board for another season of seeding to boost the city’s water supplies and will continue a long-running program for Vail and Beaver Creek.This winter, with the help of some slick Colorado State University computer models, Hjermstad hopes the operation can be fine-tuned in real time and that could mean even more snow for the Colorado mountains, upping the all-important powder quotient for Eagle County ski areas.Western Weather Consultants uses ground-based burners to disperse tiny particles of silver iodide into the path of oncoming storms. The silver iodide acts as a seeding agent, providing nuclei for the formation of snow crystals and wringing more of the available moisture from passing storms.A $100,000 Bureau of Reclamation grant, obtained by the Colorado Water Conservation Board, will fund a real-time study to measure whether the process increases snowfall from winter storms passing over the mountains. The water conservation board permits and monitors cloud-seeding operations under guidelines spelled out by the state’s weather modification program.Colorado State University researchers will track storms day-to-day, comparing predicted and actual snowfall accumulations in areas targeted by seeding and in control areas, where there is no seeding.The researchers will use computer-generated weather models to predict anticipated snowfall from a given storm and then factor in cloud-seeding data and snowfall tallies from remote sensing stations to try and detect whether the seeding is working.Hjermstad says he hopes to use the results of the modeling to fine-tune the seeding operation even as it is in progress this winter.”This is the first time this type of study will be done on a real-time basis,” says Hjermstad. “We’ll be trying to identify trends of how well the computer models can look at this.”By analyzing the storms as they progress especially the winds around mountaintop levels, Hjermstad may be able to change the rate of seeding or fire up different generators to increase the efficiency of the operation.While Hjermstad and Vail Resorts officials swear by cloud seeding, a series of studies may germinate some doubt among scientifically minded skeptics.For example, two studies commissioned by Denver Water last year showed conflicting results. A statistical analysis of snowfall data indicated the seeding was effective, boosting accumulations by about 14 percent.But a second study, aimed at tracing the silver iodide in 10 target areas, found only one site with significant silver iodide concentrations.”The lack of silver enhancement in the snowpack means the (silver iodide) plumes were not routinely transported over the sampling location. Such a finding indicates a failure to routinely seed the intended cloud regions,&quot the report concluded.The most recent report, issued in mid-October by the National Research Council, an arm of the National Academy of Sciences, is also inconclusive. The report found that, “Evaluation methodologies vary, but in general do not provide” substantial proof.”Although there is physical evidence that seeding affects cloud processes, effective methods for significantly modifying the weather generally have not been demonstrated,” the researchers conclude.The report says that, even as the science of meteorology has improved, there has been a decline in weather modification research.”Extravagant claims, unrealistic expectations, and failure to provide scientifically demonstrable success are among the factors responsible for this decline. Significantly, every assessment of weather modification dating from the first National Academies’ report in 1964 has found that scientific proof of the effectiveness of cloud seeding was lacking,” according the report.The report recommends development of a coordinated national program to conduct sustained research in the areas of cloud and precipitation microphysics, cloud dynamics, cloud modeling, and cloud seeding.”The research should not focus on near-term operational applications of weather modification; rather it should address fundamental research questions from these areas,” the report concludes.

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