Transcript TakleWatershedMeeting - Department of Geological

Trends in Iowa Precipitation:
Observed and Projected Future Trends
Eugene S. Takle
Director, Climate Science Initiative
Professor of Atmospheric Science
Department of Geological and Atmospheric Sciences
Professor of Agricultural Meteorology
Department of Agronomy
Iowa State University
Ames, Iowa 50011
[email protected]
A Watershed Year: Anatomy of the Iowa Floods of 2008
Lessons Learned – Preparing for the Future
Des Moines, Iowa
9 March 2010
Observed Trends
in Iowa Precipitation
State-Wide Average Data
State-Wide Average Data
37.5”
31.5”
19% increase
State-Wide Average Data
Totals above 40”
2 years
8 years
State-Wide Average Data
Cedar Rapids Data
28.0”
32% increase
37.0”
Cedar Rapids Data
7.8”
51% increase
11.8”
Cedar Rapids Data
20.2”
34% increase
26.8”
“One of the clearest trends in the
United States observational record
is an increasing frequency and
intensity of heavy precipitation
events… Over the last century
there was a 50% increase in the
frequency of days with
precipitation over 101.6 mm (four
inches) in the upper midwestern
U.S.; this trend is statistically
significant “
Karl, T. R., J. M. Melillo, and T. C. Peterson, (eds.), 2009:
Global Climate Change Impacts in the United States.
Cambridge University Press, 2009, 196pp.
Cedar Rapids Data
4.2 days
57% increase
6.6 days
Cedar Rapids Data
Years having more
than 8 days
11
2
4.2 days
57% increase
6.6 days
Great Flood of 1993 in the US Midwest:
A New “Great Lake”
Historical Data indicate this should
happen about once every 500 years
Lakshmi, V., and K. Schaaf, 2001: Analysis of the 1993 Midwestern flood using satellite and ground data. IEEE Trans. Geosci & Remote Sens.,
39, 1736-1743.
Projected Future Trends
in Iowa Precipitation
“The future isn’t what it used
to be”
Yogi Berra
Global Carbon Emissions (Gt)
Actual emissions are exceeding worst
case scenarios projected in 1990
Source: Jerry Meehl, National Center for Atmospheric Research
Karl, T. R., J. M. Melillo, and T. C. Peterson, (eds.), 2009: Global Climate Change Impacts in the United States. Cambridge University Press, 2009, 196pp.
Karl, T. R., J. M. Melillo, and T. C. Peterson, (eds.), 2009: Global Climate Change Impacts in the United States. Cambridge University Press, 2009, 196pp.
Low confidence
Karl, T. R., J. M. Melillo, and T. C. Peterson, (eds.), 2009: Global Climate Change Impacts in the United States. Cambridge University Press, 2009, 196pp.
Trend of increase
in occurrence of
heavy precipitation
over the 20th C is
consistent with
increasing GHG
concentrations.
Frequency of
intense
precipitation
events is likely to
increase in the
future.
Karl, T. R., J. M. Melillo, and T. C. Peterson, (eds.), 2009:
Global Climate Change Impacts in the United States.
Cambridge University Press, 2009, 196pp.
Relationship of Streamflow
to Precipitation in Current
and Future Climates
Relationship of Streamflow
to Precipitation in Current
and Future Climates
SWAT (RegCM2):
21 % increase in precip
-> 50% increase in
streamflow
DrainMod (RegCM2):
24 % increase in precip
-> 35% increase in tile
drainage
DrainMod (HIRHAM):
32 % increase in precip
-> 80% increase in tile
drainage
Will These Iowa Precipitation Trends
Continue?
Caution: These are my speculations!!
 In the short-term (next 5-10 years) precipitation
characteristics will be dominated by natural variability
from base conditions of the past 30 years (not long-term
averages)
 If we continue to have high spring and summer rainfall
and soil moisture, we likely will continue to have higher
chances of flooding
 In the longer term (>50 years), hot summers, milder
winters, and higher variability of precipitation will
become more dominant
 Failure to limit global carbon emissions will accelerate
trends toward more extremes of precipitation compared
to the 20th Century
For More Information
 North American Regional Climate Change
Assessment Program: http://www.narccap.ucar.edu/
 For current activities on the ISU campus, regionally
and nationally relating to climate change see the
Climate Science Initiative website:
http://climate.agron.iastate.edu/
 Contact me directly: [email protected]