From University of Arizona (US) : “Mapping Extreme Snowmelt and its Potential Dangers”

From University of Arizona (US)


Media contact:
Mikayla Mace Kelley
Science Writer, University Communications

Researcher contact:
Xubin Zeng
Department of Hydrology and Atmospheric Sciences

Rapid snowmelt can be dangerous, and understanding its drivers is important for understanding the world under the influence of climate change.

Rising temperatures are the main source of extreme snowmelt events, but relatively warm rainwater falling on snow is also a driver in many parts of the country.

Snowmelt – the surface runoff from melting snow – is an essential water resource for communities and ecosystems. But extreme snow melt, which occurs when snow melts too rapidly over a short amount of time, can be destructive and deadly, causing floods, landslides and dam failures.

To better understand the processes that drive such rapid melting, researchers set out to map extreme snowmelt events over the last 30 years. Their findings are published in a new paper in the Bulletin of the American Meteorological Society.

“When we talk about snowmelt, people want to know the basic numbers, just like the weather, but no one has ever provided anything like that before. It’s like if nobody told you the maximum and minimum temperature or record temperature in your city,” said study co-author Xubin Zeng, director of the UArizona Climate Dynamics and Hydrometeorology Center and a professor of atmospheric sciences. “We are the first to create a map that characterizes snowmelt across the U.S. Now, people can talk about the record snowmelt events over each small area of 2.5 miles by 2.5 miles.”

Zeng and lead study author Josh Welty, who received his doctoral degree under Zeng’s advising, created a map that catalogs the top-10 extreme snowmelt events in terms of frequency, magnitude, temperature and precipitation over every 2.5-mile square of the U.S. between 1988 and 2017. They also used machine learning to understand how large-scale weather patterns affect extreme snow melt.

The map shows the greatest amount of snow loss over a two day period across the United States within a 30-year window. The largest snow loss, indicated by green and blue, occurs in the mountains of the western United States. Units are millimeters of snow mass lost per two days. Only pixels, which equate to 2.5 square miles each, with extreme snow loss (exceeding 50 mm per two days) are included. Credit: Josh Welty.

They found that in the western half of the country, winds transport water vapor from the Pacific Ocean eastward. However, in the eastern half of the country, weather patterns transport moisture primarily south to north from the Gulf of Mexico all the way to the Great Lakes and New England.

Their maps also reveal that in most cases, extreme snowmelt is caused by unusually warm temperatures. This conclusion is fairly intuitive, but a surprising finding revealed that in certain regions, particularly in the Pacific Northwest and the northeastern U.S., extreme snowmelt events are driven by rain – which is relatively warm – falling on snow. In these cases, extreme snowmelt events become immediately dangerous.

The paper outlines one such example in detail: The Oroville Dam in Butte County, California, holds the second-largest reservoir in the state. In 2017, a series of storms dropped huge amounts of warm rain on the snowcapped Sierra Nevada Mountains, resulting in rapid snowmelt that filled the dam past its brim. Spillways, which provide controlled water runoff, failed, and over 180,000 people were evacuated.

Such events might happen more often in the future, according to Zeng and Welty’s findings. The researchers found only a slight increase in the frequency of such events over the 30-year period, and they didn’t see a trend in terms of the magnitude of extreme snowmelt events. However, 30 years isn’t long enough to establish a trend, said Zeng, who is also the Agnes N. Haury Endowed Chair in Environment in the UArizona Department of Hydrology and Atmospheric Sciences. That means future research will be especially important.

“This paper serves as foundation and a reference point to see if and how things will be changing in different regions over the next 10 to 15 years,” Welty said.

See the full article here .

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As of 2019, the University of Arizona (US) enrolled 45,918 students in 19 separate colleges/schools, including the UArizona College of Medicine in Tucson and Phoenix and the James E. Rogers College of Law, and is affiliated with two academic medical centers (Banner – University Medical Center Tucson and Banner – University Medical Center Phoenix). UArizona is one of three universities governed by the Arizona Board of Regents. The university is part of the Association of American Universities and is the only member from Arizona, and also part of the Universities Research Association(US). The university is classified among “R1: Doctoral Universities – Very High Research Activity”.

Known as the Arizona Wildcats (often shortened to “Cats”), the UArizona’s intercollegiate athletic teams are members of the Pac-12 Conference of the NCAA. UArizona athletes have won national titles in several sports, most notably men’s basketball, baseball, and softball. The official colors of the university and its athletic teams are cardinal red and navy blue.

After the passage of the Morrill Land-Grant Act of 1862, the push for a university in Arizona grew. The Arizona Territory’s “Thieving Thirteenth” Legislature approved the UArizona in 1885 and selected the city of Tucson to receive the appropriation to build the university. Tucson hoped to receive the appropriation for the territory’s mental hospital, which carried a $100,000 allocation instead of the $25,000 allotted to the territory’s only university (Arizona State University(US) was also chartered in 1885, but it was created as Arizona’s normal school, and not a university). Flooding on the Salt River delayed Tucson’s legislators, and by they time they reached Prescott, back-room deals allocating the most desirable territorial institutions had been made. Tucson was largely disappointed with receiving what was viewed as an inferior prize.

With no parties willing to provide land for the new institution, the citizens of Tucson prepared to return the money to the Territorial Legislature until two gamblers and a saloon keeper decided to donate the land to build the school. Construction of Old Main, the first building on campus, began on October 27, 1887, and classes met for the first time in 1891 with 32 students in Old Main, which is still in use today. Because there were no high schools in Arizona Territory, the university maintained separate preparatory classes for the first 23 years of operation.


UArizona is classified among “R1: Doctoral Universities – Very high research activity”. UArizona is the fourth most awarded public university by National Aeronautics and Space Administration(US) for research. UArizona was awarded over $325 million for its Lunar and Planetary Laboratory (LPL) to lead NASA’s 2007–08 mission to Mars to explore the Martian Arctic, and $800 million for its OSIRIS-REx mission, the first in U.S. history to sample an asteroid.

The LPL’s work in the Cassini spacecraft orbit around Saturn is larger than any other university globally. The UArizona laboratory designed and operated the atmospheric radiation investigations and imaging on the probe. UArizona operates the HiRISE camera, a part of the Mars Reconnaissance Orbiter. While using the HiRISE camera in 2011, UArizona alumnus Lujendra Ojha and his team discovered proof of liquid water on the surface of Mars—a discovery confirmed by NASA in 2015. UArizona receives more NASA grants annually than the next nine top NASA/JPL-Caltech(US)-funded universities combined. As of March 2016, the UArizona’s Lunar and Planetary Laboratory is actively involved in ten spacecraft missions: Cassini VIMS; Grail; the HiRISE camera orbiting Mars; the Juno mission orbiting Jupiter; Lunar Reconnaissance Orbiter (LRO); Maven, which will explore Mars’ upper atmosphere and interactions with the sun; Solar Probe Plus, a historic mission into the Sun’s atmosphere for the first time; Rosetta’s VIRTIS; WISE; and OSIRIS-REx, the first U.S. sample-return mission to a near-earth asteroid, which launched on September 8, 2016.

UArizona students have been selected as Truman, Rhodes, Goldwater, and Fulbright Scholars. According to The Chronicle of Higher Education, UArizona is among the top 25 producers of Fulbright awards in the U.S.

UArizona is a member of the Association of Universities for Research in Astronomy(US), a consortium of institutions pursuing research in astronomy. The association operates observatories and telescopes, notably Kitt Peak National Observatory(US) just outside Tucson. Led by Roger Angel, researchers in the Steward Observatory Mirror Lab at UArizona are working in concert to build the world’s most advanced telescope. Known as the Giant Magellan Telescope(CL), it will produce images 10 times sharper than those from the Earth-orbiting Hubble Telescope.

Giant Magellan Telescope, 21 meters, to be at the NOIRLab(US) National Optical Astronomy Observatory(US) Carnegie Institution for Science’s(US) Las Campanas Observatory(CL), some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high.

The telescope is set to be completed in 2021. GMT will ultimately cost $1 billion. Researchers from at least nine institutions are working to secure the funding for the project. The telescope will include seven 18-ton mirrors capable of providing clear images of volcanoes and riverbeds on Mars and mountains on the moon at a rate 40 times faster than the world’s current large telescopes. The mirrors of the Giant Magellan Telescope will be built at UArizona and transported to a permanent mountaintop site in the Chilean Andes where the telescope will be constructed.

Reaching Mars in March 2006, the Mars Reconnaissance Orbiter contained the HiRISE camera, with Principal Investigator Alfred McEwen as the lead on the project. This National Aeronautics and Space Administration(US) mission to Mars carrying the UArizona-designed camera is capturing the highest-resolution images of the planet ever seen. The journey of the orbiter was 300 million miles. In August 2007, the UArizona, under the charge of Scientist Peter Smith, led the Phoenix Mars Mission, the first mission completely controlled by a university. Reaching the planet’s surface in May 2008, the mission’s purpose was to improve knowledge of the Martian Arctic. The Arizona Radio Observatory(US), a part of UArizona Department of Astronomy Steward Observatory(US), operates the Submillimeter Telescope on Mount Graham.

The National Science Foundation(US) funded the iPlant Collaborative in 2008 with a $50 million grant. In 2013, iPlant Collaborative received a $50 million renewal grant. Rebranded in late 2015 as “CyVerse”, the collaborative cloud-based data management platform is moving beyond life sciences to provide cloud-computing access across all scientific disciplines.
In June 2011, the university announced it would assume full ownership of the Biosphere 2 scientific research facility in Oracle, Arizona, north of Tucson, effective July 1. Biosphere 2 was constructed by private developers (funded mainly by Texas businessman and philanthropist Ed Bass) with its first closed system experiment commencing in 1991. The university had been the official management partner of the facility for research purposes since 2007.

U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.