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Weather grounds biking at Boulder’s Valmont Bike Park
Jan 11th
Parks and Recreation Department requests public cooperation in staying off Valmont Bike Park trails to prevent additional damage
The Parks and Recreation Department has closed Valmont Bike Park due to poor trail conditions, and is asking for public cooperation to stay off Valmont Bike Park trails to prevent further damage. Recent running, snowboarding, sledding, dog walking and biking on the trails have caused excessive damage to not only the top surfacing material, but to the base layer as well. The maintenance required to repair this damage is costly and time-consuming and will extend the re-opening date of the park due to the extra surfacing maintenance work.
“Our staff is evaluating trail and feature surfacing daily to determine if any areas of the bike park can be opened, and we will notify the public once those areas open,” said Kirk Kincannon, Parks and Recreation Department director. “However, due to moisture deep in the soil and surfacing material, no areas of the park will be opened within the next few days.”
The Boulder Mountainbike Alliance (BMA) also urged the public to refrain from using the trails at this time.
“We need your cooperation to protect the coolest bike park on Planet Earth,” said Jason Vogel, BMA president. “Warm weather does not mean Valmont Bike Park is ready to ride. We are contending with upwelling groundwater freezing subsurface as well as snowcover and snowmelt. These conditions are a perfect storm for destroying the park we’ve all worked so hard to make a reality. BMA urges all park users to respect park closures.”
CU study: less hail may increase flooding on Front Range
Jan 9th
FROM COLORADO’S FRONT RANGE BY 2070
Summertime hail could all but disappear from the eastern flank of Colorado’s Rocky Mountains by 2070, says a new study by the National Oceanic and Atmospheric Administration, the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences and the National Center for Atmospheric Research.
Less hail damage could be good news for gardeners and farmers, said lead author Kelly Mahoney, a research scientist at CIRES, but a shift from hail to rain can also mean more runoff, which could raise the risk of flash floods. “In this region of elevated terrain, hail may lessen the risk of flooding because it takes awhile to melt,” Mahoney said. “Decision makers may not want to count on that in the future.”
For the new study, published this week in the journal Nature Climate Change, Mahoney and her colleagues used “downscaling” techniques to try to understand how climate change might affect hail-producing weather patterns across Colorado.
The research focused on storms involving pea-sized and smaller hailstones on Colorado’s Front Range, a region that stretches from the foothill communities of Colorado Springs, Denver and Fort Collins up to the Continental Divide. Colorado’s most damaging hailstorms tend to occur further east and involve larger hailstones not examined in this study.
In the summer in Colorado’s Front Range above about 7,500 feet, precipitation commonly falls as hail. Decision makers concerned about the safety of mountain dams and flood risk have been interested in how climate change may affect the amount and nature of precipitation in the region.
Mahoney and her colleagues began exploring that question with results from two climate models, which assumed that levels of climate-warming greenhouse gases will continue to increase in the future, from about 390 parts per million in the atmosphere today to about 620 parts per million in 2070.
But the weather processes that form hail, like thunderstorms, occur on much smaller scales than can be reproduced by global climate models. So the team “downscaled” the global model results twice: first to regional-scale models that can take regional topography and other details into account, then again to weather-scale models that can resolve individual storms and even the cloud processes that create hail. The regional-scale topography step was completed as part of NCAR’s North American Regional Climate Change Assessment Program.
Finally, the team compared the hailstorms of the future, from 2041 to 2070, to those of the past, from 1971 to 2000, as captured by the same sets of downscaled models. Results were similar in experiments with both climate models.
“We found a near elimination of hail at the surface,” Mahoney said.
In the future, increasingly intense storms may actually produce more hail inside clouds, the team found. However, because those relatively small hailstones fall through a warmer atmosphere, they melt quickly, falling as rain at the surface or evaporating back into the atmosphere. In some regions, simulated hail fell through an additional 1,500 feet of above-freezing air in the future as compared with the past.
The research team also found evidence that precipitation events over Colorado become more extreme in the future, while changes in hail may depend on the size of the hailstones — results that will be explored in more detail in ongoing work.
Mahoney’s postdoctoral research was supported by the Postdocs Applying Climate Expertise, or PACE, program administered by the University Corporation for Atmospheric Research and funded by CIRES Western Water Assessment, NOAA and the U.S. Bureau of Reclamation. PACE connects young climate scientists with real-world problems such as those faced by water resource managers.
Co-authors of the new paper include James Scott and Joseph Barsugli of CIRES and NOAA, Michael Alexander of the NOAA Earth System Research Laboratory and Gregory Thompson of NCAR.
A mite windy in Boulder today
Dec 31st