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The Climate Extremes Index: A Southeast U.S. Perspective. Karin L. Gleason Meteorologist Climate Monitoring Branch NOAA/NESDIS/National Climatic Data Center Asheville, NC. Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009.

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The Climate Extremes Index: A Southeast U.S. Perspective

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The Climate Extremes Index:

A Southeast U.S. Perspective

Karin L. Gleason

Meteorologist

Climate Monitoring Branch

NOAA/NESDIS/National Climatic Data Center

Asheville, NC

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Overview -

  • History of the Climate Extremes Index (CEI)

  • Operational Contiguous U.S. (CONUS) CEI and results

  • Trends in national/regional temperature and precipitation

  • Compare/Contrast CONUS CEI with Southeast (SE) Region CEI results

  • Summary/Conclusions

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- History of the Climate Extremes Index (CEI) -

  • First introduced in 1996 (Karl et al.) to quantify observed changes in climate within the CONUS

  • General lack of observational data on extremes

  • Provided a means to communicate with policy makers regarding our understanding of changes in climate

  • The Climate Extremes Index (CEI) was developed as a “first-glance” monitoring tool to help identify possible trends in a variety of climate extremes indicators

  • Originally looked at historical data (1+ years old) on an annual basis

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- History of the Climate Extremes Index (CEI) – cont’d

  • CEI is comprised of five indicators which illustrate possible extremes in:

  • - monthly mean maximum and minimum temperature

  • - extreme 1-day precipitation

  • - the number of days with/without precipitation

  • - the Palmer Drought Severity Index (PDSI)

  • “Extremes” are defined as occurrences much above/below normal (outside the 90th/10th percentile value) over the period of record – therefore expected extremes average is 20%

  • The area of the CONUS with extreme conditions is compared with the remainder of the CONUS to yield an extreme fraction for a given period

  • The CEI has been updated to include a tropical system component and is calculated for multiple seasons and on an operational basis (updated monthly)

  • Additions and modifications to original index are explained in “A Revised U.S. Climate Extremes Index” (Gleason et al. 2008)

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- History of the Climate Extremes Index (CEI) – cont’d

  • The CEI is the arithmetic average of the following indicators of the percentage of the CONUS area:

  • The sum of the percentage of the CONUS with maximum temperatures (a) much below normal and (b) much above normal.

  • The sum of the percentage of the CONUS with minimum temperatures (a) much below normal and (b) much above normal.

  • The sum of the percentage of the CONUS in (a) severe drought and with (b) severe moisture surplus based on the PDSI.

  • Twice the value of the percentage of the CONUS with a much greater than normal proportion of precipitation derived from extreme 1-day precipitation events.

  • The sum of the percentage of the CONUS with a much greater than normal number of days (a) with precipitation and (b) without precipitation.

  • The sum of squares of CONUS landfalling tropical storm and hurricane wind velocities scaled to the mean of the first five indicators (currently experimental).

  • Expected (mean) value for CEI and components is 20%

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Operational CONUS CEI and Results -

  • Noticeable/steady upward trend in CONUS CEI since about 1970

  • Primarily the result of increasing extremes in max/min temperatures, 1-day precipitation and PDSI (both wet & dry)

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Operational U.S. CEI and Results – cont’d

1-Day Prcp

Tmax

Tmin

PDSI

  • Combined percentages for annual period show upward trend in extremes in these four indicators over the last 30+ years

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Southeast Region -

  • Southeast Region includes:

  • Virginia

  • North Carolina

  • South Carolina

  • Georgia

  • Alabama

  • Florida

(Karl and Koss, 1984)

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Southeast Region versus CONUS Trends -

  • Temperature & precipitation trends for the SE are not as large as in other parts of the U.S.

  • Would expect to see fewer extremes in CEI across SE region as compared with CONUS

SE Trend: +0.26°F/Century

SE Trend: +1.25%/Century

CONUS Trends:

+1.28°F/Century

+6.10%/Century

Data: NCDC, Plots: EPA

Period of record: 1901-2008

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Southeast Region CEI Results -

  • Annual: Slight upward trend from about 1950 to present in SE CEI with a lot of inter-annual variability (CONUS CEI less variable from year to year and more pronounced upward trend)

  • PDSI and 1-day precipitation largest contributors to increase in SE CEI trend

CONUS Region

Southeast Region

+6%/decade over last 30 yrs

+4%/decade over last 30 yrs

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Southeast Region CEI Results – cont’d

  • Annual: Extremes in wet/dry PDSI periods as well as elevated extremes in 1-day precipitation were the only indicators with above expected extremes over the last 2-3 decades in SE.

Southeast Region

PDSI

1-Day Prcp

Tmin

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Southeast Region CEI Results – cont’d

  • Annual: Extremes in monthly maximum & minimum temperatures across SE appear to have transitioned from cool to warm from 1960 to present – (though little overall trend in combined percentage)

Southeast Region

Tmax

Tmin

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Seasonal CEI Results Comparisons -

  • Annual: US CEI temperature extremes are few in the 1960s, but show consistent increase post-1970 and tend to be warmer extremes – (steady upward trend in extremes in combined percentage)

CONUS Region

Tmax

Tmin

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Seasonal CEI Results Comparisons – cont’d -

  • Peak of mid-1930s drought in the High Plains didn’t include SE

Southeast PDSI

CONUS PDSI

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Seasonal CEI Results Comparisons – cont’d -

  • Summer: Similar trends in extreme extent for 1-day precipitation in the CONUS and SE regions (approx. +1%/decade from the mid-70s to the present)

Southeast Region

CONUS Region

1-Day Prcp

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Seasonal CEI Results Comparisons – cont’d -

  • Spring: SE CEI warm minimum temperature extremes not as extensive/consistent as CONUS CEI over last 20 years

Southeast Region

CONUS Region

Tmin

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Summary/Conclusions -

  • A regional CEI helps to visualize and quantify the magnitude and type of extremes which may be affecting certain parts of the country

  • Extremes observed across the SE Region over the last 30 years are not necessarily increasing at the same rate as those observed across the CONUS region

  • Timing of extreme events varies from region to region (e.g. 1930s drought)

  • More inter-annual variability with SE CEI as compared with CONUS CEI (and likely other regions)

  • Annual: SE CEI increasing but not at same rate as the CONUS CEI over last 30 years

  • Annual: Extremes in PDSI and 1-day precipitation are the primary contributors to an increasing SE CEI over last 20-30 years

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- Summary/Conclusions – cont’d -

  • Annual: Little overall trend in max/min temperature extremes in SE, yet evident shift from cold to warm extremes from 1960s to present

  • Summer: Extremes in 1-day precipitation for both CONUS and SE are increasing over the last 30 years

  • Summer: Extremes in minimum temperatures are on rise for both SE and CONUS regions and cool extremes dominate SE region from 1960s to 1970s

  • Spring: Warm minimum temperature extremes across SE not as extensive as seen across the CONUS over last 20 years

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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The Climate Extremes Index: A Southeast U.S. Perspective

- For Additional Information -

  • NCDC’s Climate Monitoring Branch Products:

  • http://www.ncdc.noaa.gov/climate-monitoring/

  • The Climate Extremes Index (CEI) Web Page:

  • http://www.ncdc.noaa.gov/oa/climate/research/cei/cei.html

  • Regional CEI plots and data (for all 9 regions) will likely become operational in 2010

  • Contact: Karin.L.Gleason@noaa.gov

Carolinas and Virginia Climate Conference

Wilmington, NC October 20-21, 2009


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