(Jackie Allen, a frequent contributor to the dri news, spent time with Dr. David Kingsmill in April and filed this report.)
It was around 400 B.C. that Aristotle wrote his treatise on atmospheric phenomena, Meteorologica, from which we've derived our modern term "meteorology." Some 2,400 years later, understanding and predicting the weather is no less fascinating to modern man who, with 24-hour television stations devoted to the subject, has a much better handle on the weather's whims than the most educated of the Greek philosophers.
Still, for all the accessible technology, people who live in northern Nevada have learned to rely as much on our aching joints and open windows as on the seemingly confident proclamations of our smiling news anchors. What's so difficult about understanding and forecasting weather patterns in the Truckee Meadows and other intermountain communities like it? Dr. David Kingsmill of DRI's Atmospheric Sciences Center is busy answering that very question.
"There is far more complex topography in the Reno area than I ever thought before moving here," Kingsmill observes. "There is the Sierra, of course, but also lots of interesting smaller mountain ranges-the Pine Nuts, the Pah Rahs-not to mention the Carson Sink and the Carson Valley. These things combine to create a lot of interesting airflow patterns and areas of convergence, where air masses are bumping into each other."
Undaunted by the eccentric terrain, Kingsmill is currently operating two devices that he hopes will help both scientists and residents better understand Western Nevada's capricious weather. One is a Doppler radar station located near DRI's Northern Nevada Science Center in north Reno, and the other a Doppler SODAR (Sound Detection and Ranging) system located at the University of Nevada, Reno's Agricultural Experiment Station in east Reno. The SODAR system is a cooperative project with the National Weather Service, with support from the Cooperative Institute for Atmospheric Sciences and Terrestrial Applications; and Kingsmill hopes the Doppler station will also become a cooperative venture. He notes that they share a common goal, namely to "improve the understanding of weather in western Nevada and, as a result, improve our ability to forecast it."
Mind you, the Truckee Meadows was not completely without weather-watching technology before Kingsmill's projects. The Weather Service continuously operates its own NEXRAD (NEXTgenerationRADar) Doppler radar on Virginia Peak, about 15 miles northeast of downtown Reno, and releases weather balloons twice daily from the northern hills to gauge winds, temperature, and moisture. While these provide a crucial regional picture for scientists and forecasters, they don't always paint an accurate picture of what's happening on the valley floor.
As if to ensure that I didn't miss this key point, a wet spring snowstorm whirled around me as I drove through Reno to meet with Kingsmill. When I arrived, soggily, in his office, he showed me a computer screen displaying Weather Service radar images indicating that there was "not much going on down here." My wet feet begged to differ, and Kingsmill explained the discrepancy. "This is a shallow, low-based storm. The Weather Service radar is located at about 8,500 feet, and so is probably cutting through just the top of the cloud and missing the bulk of the precipitation."
The problem in an intermountain area, explains Kingsmill, lies in the location of the radar. Put the radar on the valley floor, and you get a great picture of current conditions but no ability to monitor incoming systems. From a higher elevation, like that of the Weather Service radar, there is excellent surveillance of about 100 kilometers; but the sweep is not low enough to see what's happening in the valley. Kingsmill's radar, located at an elevation of about 5,000 feet, is designed to "fill in the gap" and detect the precipitation falling from, for instance, a low-lying winter storm. It will also provide a better picture of summer storms in the area, which often present the opposite problem.
"In the summer, you get these thunderstorms with very high bases. Those clouds are way up there, above the Sierra peaks; and you'll often see these bands of precipitation, called Virga shafts, falling from them. Now, the lowest beam of the high-elevation radar is seeing the precipitation, but it's not telling us what reaches the ground." Again, any long-time resident can tell you that the rain often doesn't make it to the ground at all. Instead, it evaporates in the deep layer of dry air below the base of the thunder clouds. The lower elevation radar will help researchers and forecasters make much better estimates of how much rain and snow actually reach the valley floor.
Kingsmill's SODAR project takes on another of the region's unpredictable weather components-the wind. SODAR is, in principle, very much like radar, sending out sound waves rather than electromagnetic waves. These sound waves are then bounced back to create a picture of the surrounding atmosphere. Three antennae, housed in pentagon-shaped cylinders and looking something like space-age versions of a medieval ruin, point upward in three directions: one vertical, one 30 degrees to the north, and one 30 degrees to the west. They alternately emit a high-pitched "beep" every six to seven seconds and then "listen" for that sound to come back, bounced off the temperature variations of the surrounding air mass. The resulting measurements create a picture of air temperature and movement in the area and provide a means to make short-term forecasts of wind movements. This will help those who issue wind warnings to issue them with more lead time and greater certainty. It may also alert air quality managers when a winter inversion may lead to high particulate levels in the valley. It will help researchers like Kingsmill understand and predict the timing of the area's summertime "zephyrs" that regularly sweep across the valley disrupting backyard barbecues.
Both the SODAR and lower-elevation radar also have the potential for contributing to aviation safety in the area. Intermountain airports like Reno-Tahoe International are infamous for bumpy landings, and various types of wind shear-dramatic shifts in wind speed and direction-are often to blame. One type of wind shear can occur when summer thunderstorms create a condition called microbursts. When saturated air from high elevations meets the very dry layer of air nearer the surface, the water in the moist air will evaporate very quickly, causing rapid cooling and a dense pool of air that can descend very rapidly. The downdraft then hits the surface and spreads outward, creating turbulent air near the surface-and nervous passengers in the descending aircraft. Wind shear problems can also occur in the winter, when an inversion traps cold air near the valley floor. As winds descending from the mountains move across the inversion barrier, they create turbulent conditions. "A localized radar system, which many larger airports have," explains Kingsmill, "could monitor for such conditions and warn aircraft of the potential for danger."
For all the detail that the new radar and SODAR systems will add to our weather picture, neither technology is particularly new or unusual. Their benefits are derived mainly from their strategic placement near or at the valley floor. What's more, both were acquired by DRI for very little cost, having been part of a now-defunct weather modification program in Texas run by the National Oceanic and Atmospheric Administration (NOAA). Arlen Huggins, a long-time leader and innovator in DRI's own weather modification research, knew of the existence of the equipment and was able to convince NOAA that DRI could put it to use in its atmospheric research projects. Currently, the SODAR is operating continuously from its peaceful pasture and compiling readings that can be accessed at: http://www.dri.edu/Projects/Radar/SODAR/. Kingsmill's radar is also at its post-visible as the two small white domes on the hills just north of Reno.
Unlike the Weather Service radar at Virginia Peak, which operates continuously, the DRI radar runs episodically-when something interesting is happening with the weather and when operational funds are available. "It's not designed to run on its own, at this point," says Kingsmill. "Our first priority will be to integrate it with what the National Weather Service radar is doing."
Aristotle would no doubt be amazed that we can "listen" to the wind and send out invisible waves to tell us of impending rain. But, despite these wonders, we're still a long way from being able to foretell our weather future with anything close to complete accuracy. By putting existing technology to the best possible use, Kingsmill is helping create a clearer, more detailed picture of the forces at work behind the world's weather and leading us one step closer to truly understanding it.
Jackie Allen
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