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A Significant Breakthrough in Cloud Seeding
등록일 : 2017-06-30 00:54 | 최종 승인 : 2017-06-30 00:54
Althusser Wright

[리서치페이퍼=Althusser Wright 기자]

Cloud Seeding by Pearson Scott Foresman / Wikimedia Commons

Cloud seeding is a form of weather modification, a way of changing the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud.

Earlier in the year researchers were looking for something and after 4 attempts they finally found it.  A crew of atmospheric scientists, meteorologists, and students congregated near Snake River Basin in Idaho.  The basin is a horseshoe-shaped depression nestled in between ranges of the Rocky Mountains that can be 125 miles at its widest point.

The state's notorious spuds mostly come from this tillable land.  Any day that the weather was just right, meaning when the clouds contained the perfect amount of supercooled moisture and were the ideal temperature at the right altitude, the team get in their planes and flew up to do some work.  They would fly into the center ripe clouds and drop silver iodide to see if it would manufacture extra snow (cloud seeding).  Cloud seeding has been going on in some form for about 70 years, but there still is not substantiated evidence that the practice actually works and if so how much it works.

Can they make it snow from this method or not?

Well, that's what SNOWIE is here for.SNOWIE is Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment and its mission is to prove once and for all if cloud seeding is effective or not to produce snowfall.Bob Rauber, has been studying the phenomenon since the 1970's and is one of SNOWIE's principal ­investigators and a professor of atmospheric science at the University of Illinois at Urbana-­Champaign says "These questions have been around since it started and we don't know if it's right because we haven't been able to validate it."

January 19, 2017, was the fifth attempt.  On that day Assistant Professor of Atmospheric Science at the University of Wyoming, Jeff French went up in a small King Air propeller plane.  The pilot took French to about 14,000 feet and then down to 12,000 to find the absolute best space in the clouds for supercooled liquids where the temperature is between 5 and 14 degrees Fahrenheit.

The plane was equipped with several instruments to measure things like water vapor, wind, temperature, and atomic pressure.The measurements are read by a computer processor set crammed into the four-seater airplane.  

Simultaneously another aircraft from 1,000 feet above French was dropping silver iodide, and if they succeeded snow would drift over the mountains.  French could see nothing as his plane cruised through the clouds but his instruments were there to catch the action.  They could detect surges in reflectivity that meant ice crystals were forming, watch them travel with the weather, and perhaps figure out whether snow actually appeared where the silvery chemicals had fallen.  Radars at two remote mountain sites manned by students who had to snowmobile up to the sites were scanning for the same type of measurements, were the first ones to see the zigzag suggesting snow was actually made.

Synthetic weather modification is a homerun for scientists to say the least.  Mountains play a major role in this since they help create and steer precipitation.  Air will approach a mountain and rise with the terrain while this is happening the air cools super-fast and then is condensed into an "orographic" cloud (Orographic clouds are clouds that develop in response to the forced lifting of air by the earth's topography).

Snowflake by Alexey Kljatov / Wikimedia Commons

Natural snowflake embryos often form inside clouds when ice crystals grow on tiny particles that are similar to gas or dust or pollution.  These are termed nuclei by scientists.  The saying goes to make more snow, add nuclei.  The reason why silver iodide sprinkles are used is due to the fact that when they collide with supercooled liquid water, they, in turn, make the water freeze as long as the temperature is below 21 degrees Fahrenheit.  

Drought-dry regions and ski resorts alike send silver into the sky on a regular basis and in that process spend millions of dollars, however, they cannot be sure according to scientific evidence that it is working for them.

The Cooperative Institute for Research in Environmental Sciences, a collaboration between the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder came within a hair of proving the cloud seeding actually worked.  The performed a decade of snow-based research and concluded in a 148-page review that "It is reasonable to conclude that artificial enhancement of winter snowpack over mountain barriers is possible." But later in the same paragraph the authors ambiguously stated: "No rigorous scientific study has demonstrated that seeding winter orographic clouds increases snowfall.As such, the 'proof' the scientific community has been seeking for many decades is still not in hand."

The SNOWIE team has made a significant breakthrough here.  The have published online reports showing three instances where they found the formation of snow due to their activity.  Rauber wrote of the second time, "The seeding signatures were unmistakable and distinct, with the lines mimicking the seeder flight track." They started to believe maybe the signatures weren't a coincidence, and they wanted more.Sure enough, it paid off.

"The remarkable thing was not that we saw it," says Friedrich, "but that we were able to repeat it multiple times."

It should be noted that they haven't fully analyzed the data.Their results have not undergone peer review and been published in an academic journal.  They still have a lot of work to do before they can put it out for the world to see exactly how, and how well, cloud seeding can work.They'll be ­digging into data for four to six years, although they are shooting to get the ­whiz-bang results out within 12 months.

Of SNOWIE's data, Derek Lestrud, a meteorologist with Idaho Power and president of the North American Weather Modification Council—said, "What we got was well above and beyond what anybody imagined."

[리서치페이퍼=Althusser Wright 기자]
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