New study shows robust increases in atmospheric thirst across much of U.S. during past 40 years

Apr 6, 2022 | Announcements, News releases

April 6, 2022
RENO, Nev.

Atmospheric Thrist
Temperature
Climate

Above: A dry Nevada landscape. New research led by DRI scientists shows that atmospheric thirst is a persistent force in pushing Western landscapes and water supplies toward drought.

Credit: Riccardo Panella/DRI.

New study shows robust increases in atmospheric thirst across much of U.S. during past 40 years

Largest changes centered over Rio Grande region of Southwestern U.S.

A multi-dataset assessment of climatic drivers and uncertainties of recent trends in evaporative demand across the continental U.S.

The full text of the study, A multi-dataset assessment of climatic drivers and uncertainties of recent trends in evaporative demand across the continental U.S., is freely available from the Journal of Hydrometeorology: https://journals.ametsoc.org/view/journals/hydr/23/4/JHM-D-21-0163.1.xml.

Reno, Nev. (April 6, 2022) –In arid Western states, the climate is growing warmer and drier, leading to increased demand for water resources from humans and ecosystems. Now, the atmosphere across much of the U.S. is also demanding a greater share of water than it used to, according to a new study by a team from DRI, University of California, Merced, and Scripps Institution of Oceanography at UC San Diego.

The study was published in the Journal of Hydrometeorology and assessed trends in evaporative demand across the U.S. during a 40-year period from 1980-2020 using five datasets. Evaporative demand, sometimes described as “atmospheric thirst,” is a measure of the potential loss of water from the earth’s surface to the atmosphere based on variables including temperature, humidity, wind speed, and solar radiation.

The team’s findings showed substantial increases in atmospheric thirst across much of the Western U.S. during the past 40 years, with the largest and most robust increases in an area centered around the Rio Grande and Lower Colorado rivers. These regions have experienced changes on the order of two-to-three standard deviations from what was seen during the baseline period of 1980-2000.

“This means that atmospheric thirst conditions in parts of the country are now verging outside of the range that was experienced 20 to 40 years ago, especially in some regions of the Southwest,” said lead author Christine Albano, Ph.D., of DRI. “This is really important to understand, because we know that atmospheric thirst is a persistent force in pushing Western landscapes and water supplies toward drought.”

Figure showing changes in atmospheric thirst, measured in terms of reference evapotranspiration (mm), from 1980-2020. The largest changes are centered over the Rio Grande region of the southwestern U.S.

Credit: DRI.

To learn more about the role that different climate variables play in determining atmospheric thirst, Albano and her colleagues analyzed the relative influences of temperature, wind speed, solar radiation, and humidity. They found that, on average, increases in temperature were responsible for 57 percent of the changes observed in all regions, with humidity (26 percent), wind speed (10 percent), and solar radiation (8 percent) playing lesser roles.

“This study shows the dominant role that warming has played on the increasing evaporative demand and foreshadows the increased water stressors the West faces with continued warming,” said study co-author John Abatzoglou, Ph.D., of University of California, Merced.

For farmers and other water users, increases in atmospheric thirst mean that in the future, more water will be required to meet existing water needs. Some of these changes observed in this study are centered over areas where warming temperatures and lower-than-average precipitation are already creating stress on water supplies.

For example, in the Rio Grande region, the study authors calculated that atmospheric thirst increased by 8 to 15 percent between 1980 and 2020. Holding all else equal and assuming no other changes in management, this means that 8 to 15 percent more water is now required to maintain the same thoroughly-watered crop.

“Our analysis suggests that crops now require more water than they did in the past and can be expected to require more water in the future,” said study co-author Justin Huntington, Ph.D., of DRI.

Other impacts of increased atmospheric thirst include drought, increased forest fire area, and reduced streamflows.

“Our results indicate that, decade by decade, for every drop of precipitation that falls, less and less water is likely to drain into streams, wetlands, aquifers, or other water bodies,” said study co-author Michael Dettinger, Ph.D., of Scripps Institution of Oceanography and DRI. “Resource managers, policy makers, and the public need to be aware of these changes and plan for these impacts now and into the future.”

Members of the team are now developing seasonal to sub-seasonal forecasts of evaporative demand.

“We anticipate these types of forecasts will be important for drought and fire forecasting applications,” said study co-author Dan McEvoy, Ph.D., of DRI.

Additional information:

The full text of the study, A multi-dataset assessment of climatic drivers and uncertainties of recent trends in evaporative demand across the continental U.S., is freely available from the Journal of Hydrometeorology: https://journals.ametsoc.org/view/journals/hydr/23/4/JHM-D-21-0163.1.xml

The study team included Christine Albano (DRI), John Abatzoglou (UC Merced), Daniel McEvoy (DRI), Justin Huntington (DRI), Charles Morton (DRI), Michael Dettinger (Scripps Institution of Oceanography/DRI), and Thomas Ott (DRI).

This research was funded by the Sulo and Aileen Maki Endowment Fund to the Desert Research Institute’s Division of Hydrologic Sciences, the National Oceanic and Atmospheric Administration (NOAA) California-Nevada Climate Applications Program (NA17OAR4310284), NOAA National Integrated Drought Information System California-Nevada Drought Early Warning System (NA20OAR4310253C), the NASA Applied Sciences, Water Resources Program (NNX17AF53G), the U.S. Geological Survey Landsat Science Team (140G0118C0007), and USDA-NIFA project (2021-69012-35916).

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About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.

About UC Merced

UC Merced opened in 2005 as the newest member of the University of California system and is the youngest university to earn a Carnegie research classification. The fastest-growing public university in the nation, UC Merced is on the cutting edge of sustainability in campus construction and design and supports high-achieving and dedicated students from the underserved San Joaquin Valley and throughout California. The Merced 2020 Project, a $1.3 billion public-private partnership that is unprecedented in higher education, nearly doubled the physical capacity of the campus with 11 buildings earning Platinum LEED certification.

About Scripps Oceanography

Scripps Institution of Oceanography at the University of California San Diego is one of the world’s most important centers for global earth science research and education. In its second century of discovery, Scripps scientists work to understand and protect the planet, and investigate our oceans, Earth, and atmosphere to find solutions to our greatest environmental challenges. Scripps offers unparalleled education and training for the next generation of scientific and environmental leaders through its undergraduate, master’s and doctoral programs. The institution also operates a fleet of four oceanographic research vessels, and is home to Birch Aquarium at Scripps, the public exploration center that welcomes 500,000 visitors each year.

About UC San Diego

At the University of California San Diego, we embrace a culture of exploration and experimentation. Established in 1960, UC San Diego has been shaped by exceptional scholars who aren’t afraid to look deeper, challenge expectations and redefine conventional wisdom. As one of the top 15 research universities in the world, we are driving innovation and change to advance society, propel economic growth and make our world a better place. Learn more at ucsd.edu.

Daniel McEvoy Receives Board of Regents 2021 Rising Researcher Award

Mar 9, 2021 | Announcements, News releases

Reno, Nev. (Mar. 9, 2021) – Last week, the Nevada System of Higher Education (NSHE) Board of Regents named Desert Research Institute (DRI) scientist Daniel McEvoy, Ph.D., the recipient of the 2021 Rising Researcher Award. This honor is given annually to one NSHE faculty member from DRI, the University of Nevada, Reno (UNR), and the University of Nevada, Las Vegas (UNLV) in recognition of their early-career accomplishments and potential for future advancement and recognition in research.

McEvoy is an Assistant Research Professor with DRI’s Division of Atmospheric Sciences and Regional Climatologist for the Western Regional Climate Center. His research has increased our understanding of land surface-atmospheric feedbacks and evaporative processes on droughts, the connections between drought, climate, and wildland fire, and natural resource management applications of weather, climate, and satellite data.

“It is a great honor to receive this year’s Rising Researcher Award,” McEvoy said. “I look forward to continuing my work in climatology for many years to come.”

Some of McEvoy’s most recent published work describes how changes in evaporative demand (a measure of how dry the air is, sometimes described as “atmospheric thirst”) is expected to impact the frequency of extreme fire danger and drought in Nevada and California through the end of the 21st century. He specializes in using big climate data to create applied climate products such as Climate Engine and the Evaporative Demand Drought Index that can be accessed and used in real-world settings such as land and water management.

During the first five years of his career, McEvoy has given over 60 presentations at national scientific conferences and workshops, published 17 peer-reviewed publications to high-quality journals such as Geophysical Research Letters and Journal of Hydrometeorology, and has contributed to two book chapters. McEvoy has also successfully developed and funded more than a dozen grants and contracts from diverse sources such as the National Oceanic and Atmospheric Administration, California Department of Water Resources, NASA, SERVIR, and Google. These funded projects total more than $3.2 million.

McEvoy holds Ph.D. and M.S. degrees in Atmospheric Science from the University of Nevada, Reno, and a B.S. in Environmental Science from Plattsburgh State University of New York. He joined DRI in 2010 as a graduate research assistant working under advisor John Mejia, Ph.D.

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The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit  www.dri.edu.

Climate change and “atmospheric thirst” to increase fire danger and drought in Nevada and California

Nov 19, 2020 | News releases, Research findings

Climate change and “atmospheric thirst” to increase fire danger and drought in Nevada and California

RENO, NEV.
NOV 19, 2020

Climate Change
Wildfire
Drought

New study shows impacts of increased levels of evaporative demand as climate grows warmer and drier

Climate change and a “thirsty atmosphere” will bring more extreme wildfire danger and multi-year droughts to Nevada and California by the end of this century, according to new research from the Desert Research Institute (DRI), the Scripps Institution of Oceanography at the University of California, San Diego, and the University of California, Merced.

In a new study published in Earth’s Future, scientists looked at future projections of evaporative demand – a measure of how dry the air is – in California and Nevada through the end of the 21st century. They then examined how changes in evaporative demand would impact the frequency of extreme fire danger and three-year droughts, based on metrics from the Evaporative Demand Drought Index (EDDI) and the Standardized Precipitation Evapotranspiration Index (SPEI).

According to their results, climate change projections show consistent future increases in atmospheric evaporative demand (or the “atmospheric thirst”) over California and Nevada. These changes were largely driven by warmer temperatures, and would likely lead to significant on-the-ground environmental impacts.

Maps showing increases in evaporative demand toward end of next century.

Study results show increases of 13 to 18 percent in evaporative demand during all four seasons by the end of the century.

Credit: Dan McEvoy/DRI.

“Higher evaporative demand during summer and autumn—peak fire season in the region—means faster drying of soil moisture and vegetation, and available fuels becoming more flammable, leading to fires that can burn faster and hotter,” explained lead author Dan McEvoy, Ph.D., Assistant Research Professor of Climatology at DRI.

“Increased evaporative demand with warming enables fuels to be drier for longer periods,” added coauthor John Abatzoglou, Ph.D., Associate Professor with the University of California, Merced. “This is a recipe for more active fire seasons.”

The research team found that days with extreme fire danger in summer and autumn are expected to increase four to 10 times by the end of the century. Their results also showed that multi-year droughts, similar to that experienced in California and Nevada during 2012-2016, were projected to increase three to 15 times by the end of the century.

“One major takeaway was that we can expect to see a lot more days in the summer and autumn with extreme fire danger related to increased temperature and evaporative demand,” McEvoy said. “Another takeaway was that even in locations where precipitation may not change that much in future, droughts are going to become more severe due to higher evaporative demand.”

Graph showing increase in extreme fire danger days in 2020.

California and Nevada on average experienced a record-setting number of “extreme fire danger” days in 2020, as indicated by the line on the graph above. Extreme fire danger days were calculated using the Evaporative Demand Drought Index (EDDI), with methods described in McEvoy et al. (2020). Data source: http://www.climatologylab.org/gridmet.html.

Credit: Dan McEvoy/DRI.

Study authors say that the cumulative effects of increases in evaporative demand will stress native ecosystems, increase fire danger, negatively impact agriculture where water demands cannot be met, and exacerbate impacts to society during periods of prolonged dryness. Several members of the research team are part of the California-Nevada Applications Program (CNAP), and will use these study results to provide resource managers with a view of possible future scenarios.

“These results provide information to support science-based, long-term planning for fire management agencies, forest management agencies, and water resource managers,” said coauthor Julie Kalansky, Ph.D., Program Manager for CNAP. “We plan to work with partners to help integrate the findings from this paper to support building climate resilience.”

Additional Information:

This study was funded by the National Oceanic and Atmospheric Administration (NOAA) California-Nevada Climate Applications Program (CNAP) and the NOAA National Integrated Drought Information System (NIDIS) California-Nevada Drought Early Warning System.

The full text of the paper, “Projected Changes in Reference Evapotranspiration in California and Nevada: Implications for Drought and Wildland Fire Danger,” is available from Earth’s Future: https://doi.org/10.1029/2020EF001736.

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The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit  www.dri.edu.

Updated California Climate Tracker tool provides more than 120 years of climate data

Sep 10, 2018 | Announcements, News releases

Reno, NV (Sept 10, 2018) – Scientists from the Western Regional Climate Center (WRCC) at the Desert Research Institute (DRI) in Reno, NV are pleased to announce the release of a long-awaited update to a climate mapping tool called the California Climate Tracker (https://wrcc.dri.edu/Climate/Tracker/CA/).

Originally launched in 2009, the California Climate Tracker was designed to support climate monitoring in California and allows users to generate maps and graphs of temperature and precipitation by region. The 2018 upgrade incorporates substantial improvements including a more user-friendly web interface, improved accuracy of information based on PRISM data, and access to climate maps and data that go back more than 120 years, to 1895.

Map of California created with California Climate Tracker tool.

The map above, created using California Climate Tracker, shows mean temperature percentile rankings for different climatological regions in California during June – August 2018. Credit: Dan McEvoy, DRI.

“One really significant change between the old and new versions of the California Climate Tracker is that in the previous version, you weren’t able to look at archived maps,” said Daniel McEvoy, Ph.D., Assistant Research Professor of Climatology at DRI and member of the Climate Tracker project team. “Now you can say for example, ‘I want to see what the 1934 drought looked like,’ and go back and get the actual maps and data from 1934. You can also look at graphs of the data and see trends in temperature and precipitation over time.”

In addition to providing historical and modern data for regions across California, this easy-to-use web-based tool can be used to produce publication-quality graphics for reports, articles, presentations or other needs. It can be accessed for free by anyone with a standard web browser and an internet connection.

“The California Climate Tracker was initially designed and developed for use by the California Department of Water Resources, but we hope it is also useful to a much broader community of water managers, climatologists, meteorologists and researchers in California,” McEvoy said.

The map above, created using California Climate Tracker, shows precipitation percentile rankings for various climatological regions in California during October 2017 – August 2018. Credit: Dan McEvoy, DRI

The recent upgrade to this tool was the work of Nina Oakley, Ph.D., Justin Chambers, and McEvoy, all of whom are part of the Western Regional Climate Center at DRI. The original version of the California Climate Tracker tool was developed at DRI and designed by John Abatzoglou, Ph.D., now of the University of Idaho, based on a system for identifying regional patterns of climate variability within the state of California that he developed with Laura Edwards, M.S, now State Climatologist and Climate Field Specialist for the South Dakota State Climate Office, and the late Kelly Redmond, Ph.D., former regional climatologist for WRCC and DRI.

The California Climate Tracker was built with support from and in collaboration with the California Department of Water Resources. The team is currently in the process of building a similar tool for Nevada and are seeking funding partners to sponsor that work.

To access the California Climate Tracker tool, please visit: https://wrcc.dri.edu/Climate/Tracker/CA/

For more information on the Western Regional Climate Center at DRI, please visit: https://wrcc.dri.edu

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The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit  www.dri.edu.

Scientists investigate northern Sierra Nevada snow droughts

Jan 7, 2018 | News releases, Research findings

Above: From the east side of Washoe Lake, the view of Slide Mountain and Mount Rose on January 7, 2018, showed the effects of the ongoing snow drought. Warm wet and dry periods in November and a dry period in December created snow drought conditions throughout the region. Credit Benjamin Hatchett, DRI.

Reno, NV (Wednesday, January 17, 2018): The Lake Tahoe Basin and northern Sierra Nevada are currently experiencing a condition known as snow drought, according to new research and data from scientists at the Desert Research Institute (DRI). Snow droughts, or periods of below-normal snowpack, occur when abnormally warm storms or abnormally dry climate conditions prevent mountain snowpack from accumulating.

“As of early January, the snowpack in the Lake Tahoe Basin was only 28 percent of normal,” said Benjamin Hatchett, Ph.D., a postdoctoral researcher with DRI’s Division of Atmospheric Sciences. “We experienced warm wet and dry periods in November and a dry period in December that has created snow drought conditions throughout the region, followed by warm, rainy weather so far in January that has caused snowpack levels to decline further, especially at low elevation sites.”

Snow droughts have become increasingly common in the Sierra Nevada and Cascade mountains in recent years, as warming temperatures push snow lines higher up mountainsides and cause more precipitation to fall as rain.

Hatchett, an avid backcountry skier, began to notice the trend several years ago and recently published research outlining an approximately 1,200-foot rise in the winter snow levels over the last ten years across the northern Sierra Nevada.

Looking deeper into the rising snow levels and a general continued lack of snow in their local region, Hatchett and fellow DRI climate researcher Daniel McEvoy, Ph.D., an assistant research professor of climatology and regional climatologist at DRI’s Western Regional Climate Center (WRCC), sought to expand upon the little that is currently known about snow droughts and their impacts to local watersheds and economies.

In a new study recently published in the journal Earth Interactions, Hatchett and McEvoy explored the root causes of snow droughts in the northern Sierra Nevada, and investigate how snow droughts evolve throughout a winter season. To do this, they used hourly, daily and monthly data to analyze the progression of eight historic snow droughts that occurred in the northern Sierra Nevada between 1951 and 2017.

“We were interested in looking at the different pathways that can lead to a snow drought, and the different implications that each pathway has for mountain systems,” McEvoy explained.

The snow drought of 2017/2018 as observed at Fallen Leaf Lake, Calif. and the Central Sierra Snow Lab in Soda Springs, Calif. Map created by ClimateEngine.org – Powered by Google Earth Engine. Credit Benjamin Hatchett, DRI.

Previous research has used April 1st (the date that snowpack levels, measured as snow water equivalent or SWE, in the Sierra Nevada typically reach a maximum) as the primary date for calculating snow drought, and classified each snow drought as one of two types, warm or dry. “Warm snow drought” years were characterized by above-average levels of precipitation and below-average snow accumulation (SWE); “Dry snow drought” years were characterized by below-average levels of precipitation and below-average snow accumulation (SWE).

Hatchett and McEvoy’s work expanded upon these concepts by examining the progression of snow droughts throughout the entire winter season.

Their results illustrate that each snow drought originates and develops along a different timeline, with some beginning early in the season and some not appearing until later. Snow droughts often occurred as a result of frequent rain-on-snow events, low precipitation years, and persistent dry periods with warmer than normal temperatures. The severity of each snow drought changed throughout the season, and effects were different at different elevations.

“We learned that if you just look at snow levels on April 1st, you miss out on a lot of important information,” McEvoy said. “For example, if you are in a snow drought all winter long and come out of it right at the end due to a few big storms, there are probably implications to that.”

Sometimes, McEvoy explained, snow droughts were found to occur in years with above-average precipitation. For example, in 1997, a powerful atmospheric river storm event led to record-breaking flooding throughout the region – but much of the moisture arrived as rain rather than snow, with detrimental effects on the snowpack.

Climate change is likely to make snow drought an even more common phenomenon in the future, said Hatchett, as temperatures in the northern Sierra Nevada are expected to continue warming.

“There has always been an occasional snow drought year in the mountains, but that was typically the ‘dry’ type of snow drought caused by lack of precipitation,” Hatchett said. “As the climate grows warmer and more precipitation falls as rain instead of snow, we are seeing that we can have an average or above-average precipitation year and still have a well below-average snowpack.”

The implications of snow drought have not yet been studied extensively, but may include impacts to water resources, snowmelt runoff, flooding, soil moisture, tree mortality, ecological system health, fuel moisture levels that drive fire danger, human recreation, and much more. In regions such as the Lake Tahoe Basin, where mountain snowpack sustains wildlife, ecosystems, local economies, and provides crucial water resources to downstream communities throughout the year, the impacts of snow droughts could be enormous.

The last four winters, Hatchett and McEvoy noted, have all exhibited some degree of snow drought in the northern Sierra Nevada. Even the recent huge winter of 2016/17, which ended with far above-average snowpack levels (205% of the long-term median on April 1, 2017 in the Lake Tahoe Basin), began with a period of early-season snow drought during a dry November. This winter has been no exception, with snow drought taking hold over low elevation areas in November, and moving to higher elevation sites in December.

Only time will tell how the 2017/2018 winter season will end, but in the meantime, snow drought is affecting the region in ways that have not yet been fully quantified.

Hatchet and McEvoy hope that their research will prompt further investigations into the potentially devastating impacts of snow drought, and will help to inform regional climate adaptation planning efforts.

“We spend a lot of time going out and skiing, climbing, and hiking in the mountains, which is what inspired us to study these things,” Hatchett said. “We’re seeing and experiencing snow drought first-hand, and we have to quantify it and understand it because these are changing patterns on the landscape that will have massive implications for the mountain environments that we experience each day and the mountain communities that we live in.”

The full version of the study—“Exploring the Origins of snow drought in the northern Sierra Nevada, California”—is available online at –http://journals.ametsoc.org/doi/10.1175/EI-D-17-0027.1

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The Desert Research Institute (DRI) is a recognized world leader in investigating the effects of natural and human-induced environmental change and advancing technologies aimed at assessing a changing planet. For more than 50 years DRI research faculty, students, and staff have applied scientific understanding to support the effective management of natural resources while meeting Nevada’s needs for economic diversification and science-based educational opportunities. With campuses in Reno and Las Vegas, DRI serves as the non-profit environmental research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.