Precipitation extremes during 1895-2003 in the continental United States

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Precipitation extremes during 1895-2003 in the
continental United States

• Kenneth E. Kunkel
• Illinois State Water Survey
• Collaborators Dave Easterling, Kelly Redmond,
  Ken Hubbard, Connie Woodhouse, Ed Cook

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Questions

• Are the frequency and intensity of extremes
  changing?
• What is the magnitude of natural variability in
  the frequency and intensity of extremes
• What are the implications for the global change
  debate?

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• Trends in extreme precipitation
• Characteristics of early 20th Century pluvial
• Causes of observed trends

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U.S. Climate Data

• U.S. Cooperative Observer Network in operation
  since late 1880s
• Daily Observations Max and Min Temp, Precip,
  Snowfall, Snow Depth
• Digitizing of Observations began in 1948
• Miscellaneous projects resulted in the digitizing
  of selected data prior to 1948

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Until recently, digital availability of pre-1948
daily climate data has been deficient
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Climate Database Modernization Project

• U.S. Congress has appropriated funds to NOAA
  NESDIS to digitize data records
• One of the first data sets chosen for
  digitization was the daily cooperative records.
  Digitization of these records finished for the
  most part in 2001.

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Long-term Stations 1895-2003
Red new Blue - old
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Data Set Quality Control

• Basic QC of data performed by National Climatic
  Data Center
• A collaborative project, partially funded by NOAA
  OGP CCDD, to more completely QC these data has
  been completed
• Illinois State Water Survey, National Climatic
  Data Center (Dave Easterling), U. of
  Nebraska-Lincoln (Ken Hubbard), Desert Research
  Institute (Kelly Redmond)

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Extremes Definition

• Event Duration days
• Recurrence (threshold exceedance) years
• 1,5,10,30-day duration
• 1,5,20-year recurrence
• National index

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1-day duration
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1-dy,1-yr Extreme Precipitation 1895-1905
Blue positive anomaly Red negative
anomaly
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1-dy, 1-yr Extreme Precipitation 1990-2000
Blue positive anomaly Red negative
anomaly
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Current Drought in West

• High frequencies in western U.S. occurred shortly
  before 1922 Colorado River compact
• Analysis of this period reveals role of extreme
  seasons
• Compact based on 16.5 maf annual flow 1906-2001
  average was 15.1 maf paleoclimatic
  reconstructions indicate 400-year average of only
  13.5 maf

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Tree ring reconstruction

• Tree-ring reconstruction of western US climate
  recently extended back to more than 1000 years
  before present (Cook et al, Science, in press)
• Comparative analysis tree-ring reconstruction for
  early 20th Century pluvial (consecutive years of
  positive PDSI, cumulative PDSI sum) Connie
  Woodhouse, Dave Easterling, Ed Cook

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Western United States Tree-Ring Climate
Reconstruction Consecutive Years of Positive
Palmer Drought Severity Index
of years period cumulative sum average annual value
9 9 8 7 7 1076-1084 1112-1120 1424-1431 1615-1621 1911-1917 12.86 8.99 6.46 11.51 12.22 1.129 1.000 0.807 1.645 1.750
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Wettest Seasons in Western U.S.
season precipitation (mm)
winter 1908-09 winter 1968-69 winter 1939-40 spring 1995 winter 1915-16 winter 1913-14 winter 1914-15 winter 1997-98 winter 1995-96 spring 1906 winter 1940-41 winter 1979-80 winter 1910-11 winter 1905-06 winter 1935-36 209 201 196 189 182 182 182 181 180 178 178 177 176 176 175
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Causes

• Studies with GISS GCM
• North Pacific Index
• Cyclone tracks
• Klein, W. H., 1957 Principal tracks and mean
  frequencies of cyclones and anticyclones in the
  Northern Hemisphere. U.S. Weather Bureau Research
  Paper 40, 60 pp.
• U.S. Weather Bureau, Daily Synoptic Series,
  Historical Weather Maps, Northern Hemisphere Sea
  Level, January 1899 to June 1939, Cooperative
  project of U.S. Army Air Force and U.S. Weather
  Bureau, Washington DC 1944.

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CONCLUSIONS

• Heavy Precipitation Frequencies were highest
  during the late 20th Century but also rather high
  during the late 19th and early 20th Century
• The late 20th Century peak may be caused by
  Tropical Pacific SST anomalies. The early 20th
  Century peak occurs at a time of large positive
  values of the NPI and above normal frequency of
  cyclones coming ashore in the Pacific Northwest.

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THE END
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