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ISPE Faculty Spotlight
Katie Hirschboeck: taking it to extremes
February 7, 2007
By Stephanie Doster
Katie Hirschboeck
Katie Hirschboeck is all about extremes, from the floods that redesigned landscapes centuries ago to the drought that has plagued the Southwest for more than a decade.
Blending dendrochronology—the dating and study of annual rings in trees—with hydrology, geography, and climatology, Hirschboeck examines what causes such extreme events.
“The overarching theme in all of my research is the climatology of extremes and what kind of atmospheric circulation patterns lead to these,” said Hirschboeck, an associate professor with The University of Arizona’s Laboratory of Tree-Ring Research (LTRR).
A geographer, geoscientist, and climatologist by training, Hirschboeck said that dendroclimatology—the study of tree-rings to reconstruct patterns and variability of climate elements—traditionally has focused on temperature and precipitation reconstructions to address whether certain conditions in the past were hot or cool, wet or dry.
“But dendroclimatology needs to be more than that. Just as important are the delivery mechanisms leading to really wet, dry, or cold periods, and that requires a link to atmospheric circulation,” she said. “That’s where synoptic climatology comes in—taking climate patterns that tree rings are showing us and directly trying to link them to a circulation pattern.”
In her office, tucked under the stands of Arizona Stadium, Hirschboeck is currently plying her skills on the second phase of research for the Salt River Project (SRP), which provides electricity and water to millions of people in the Phoenix area. Working with her LTRR colleague David Meko, Hirschboeck is using updated tree-ring reconstructions of annual streamflow of the Salt-Verde River Basin through the dry summer of 2005 to define the relationships between tree-ring data and the weather and climate patterns that lead to high and low flow extremes in the watershed.
The project also involves examining the degree to which variation in seasonal precipitation and snow cover can be linked with the tree-ring record to provide long-term hydrologic information that is directly applicable to water-use decision making. The results, Hirschboeck said, will allow SRP water managers to place the most recent drought of the late 1990s and early 2000’s into a long-term, historical context linked to climatic variability.
“It’s designed to give water managers an idea of the probability of different kinds of severe low and high streamflow periods to assist them in making decisions,” she said. “The managers need to know how long some of the low flow periods might persist, and this is just the kind of problem that tree rings can shed light on because we can do really long reconstructions to extend the instrumental record of streamflow back in time.”
In the Southwest, trees tend to have the narrowest rings when winter precipitation is low and summer temperatures are high.
“We’re finding interesting things,” Hirschboeck said. “The year 2002, which was extremely dry in many areas of the West, is really showing up as an anomalous year. There are some cores in which you don’t even see the ring.”
In addition to her synoptic dendroclimatology work, Hirschboeck also is involved in research on other kinds of extreme events, including floods and severe freezes. She is a new investigator with the Climate Assessment for the Southwest (CLIMAS) project, where she hopes to apply her expertise in flood hydroclimatology.
Inspired by the success of the SRP project, Hirschboeck has proposed working with floodplain managers and flood warning officials to add climatic information to the Arizona Flood Warning System website. Her vision is that with a click of the mouse, users would be able to access a climatic history of the key weather patterns that have produced the major floods at a certain gage.
“It’s a way of adding a longer-term climatic perspective to the standard hydrometeorological approach used in flood analysis,” Hirschboeck said.
Another project idea involves reevaluating floodplain maps under different types of future climatological scenarios.
When she slips out of her office and into the classroom, Hirschboeck teaches climatology and dendroclimatology courses, as well as an award-winning global change general education course. It’s a wonderful opportunity to teach future citizens of this planet, she says. Her work with students spills into her role as chair of the Global Change PhD Minor Graduate Interdisciplinary Program, which aims to train graduate students who will contribute to an integrated understanding of the natural and social dynamics of global change.
The most recent scientific projections of future climate say it is very likely that the frequency of extreme events such as heavy precipitation, floods, and warm spells that impact droughts will increase. This makes it all the more important to understand how these extremes events operate, Hirschboeck said. Sorting out the climatic causes of extreme events using observations from both the observed and paleorecords will allow us to find innovative solutions to the problems that await us.