2011 Summer AERA Training 1

What’s Normal?What’s Normal?26-29 June 201126-29 June 2011

Edward J. Hopkins, Edward J. Hopkins, Assistant Wisconsin State ClimatologistAssistant Wisconsin State ClimatologistDept. of Atmospheric & Oceanic SciencesDept. of Atmospheric & Oceanic SciencesUniversity of Wisconsin-MadisonUniversity of Wisconsin-Madison

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BackgroundBackground

“Normals” – Way of depicting an expected climate state based upon

statistics over a long-time span.

What normals include:– Averages– Frequencies– Percentiles

Standardized International Agreement– National Weather Service and National Climatic Data

Center following international agreement to update the 30-year “normals” every ten years.

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Background (con’t.)Background (con’t.)

Why 30-year time length? – Climate is always changing!– Three-decade time-span deemed appropriate – Not too long to cover-up long-term changes in climate– Not too short for an uneven set of statistics due to year-

to-year or decadal changes in weather & climate.

Current climate normal interval covers 1971-2000 averaging period, but wait…

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Long-term temperature record

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Modifying the normalsModifying the normals

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Modifying the normalsModifying the normals

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Modifying the normalsModifying the normals

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Modifying the normalsModifying the normals

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Modifying the normalsModifying the normals

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Modifying the normalsModifying the normals

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Modifying the normalsModifying the normals

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New NormalsNew Normals

National Climatic Data Center is computing new normals of station – temperature (maximum, minimum and average), – precipitation, – snowfall and snow cover – heating and cooling degree day information.

Normals for all these variables will be for daily, monthly, seasonal and annual time scales.

For 250 Local Climatological Data stations:– Hourly averages will include humidity & wind

information.

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Climate StationsClimate Stations

Temperature Temperature ~7500 stations~7500 stations

PrecipitationPrecipitation~8700 stations~8700 stations

Snow Snow ~ 6400 stations~ 6400 stations

Snow depthSnow depth~5300 stations~5300 stations

Hourly Hourly ~260 stations~260 stations

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New Normals ScheduleNew Normals Schedule

1 July 2011 -- New 1981-2010 normals of temperature, precipitation & degree days made available to public.

1 Aug 2011 --NWS begins use on workstations.

31 Dec 2011 --All other normals (the “ag normals”).

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Preliminary ResultsPreliminary Results

Changes between 1971/2000 & 1981/2010 due to:– Changes in climate– Changes in stations, instruments & observing procedures

New normal temperatures – Slightly higher than previous normals for many areas of nation.– Due to inclusion of warm 2000-2009 interval.

Increases in temperature are not uniform across nation and from season to season.

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How do new normals differ?How do new normals differ?Source: A. Arguez, NCDC (Jun 2011)

Summer – Jul Max Temps

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How do new normals differ?How do new normals differ?Source: A. Arguez, NCDC (Jun 2011)

Winter – Jan Min Temps

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Changes for WisconsinChanges for Wisconsin

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Changes for WisconsinChanges for Wisconsin

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For more informationFor more information

NCDCNCDChttp://www.ncdc.noaa.gov/oa/http://www.ncdc.noaa.gov/oa/climate/normals/newnormals.htmlclimate/normals/newnormals.html

Or email Or email stclim@aos.wisc.edustclim@aos.wisc.edu from from http://www.aos.wisc.edu/~sco http://www.aos.wisc.edu/~sco

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The Wisconsin State Climatology Office Web PageThe Wisconsin State Climatology Office Web Page

http://www.aos.wisc.edu/~scohttp://www.aos.wisc.edu/~sco

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Views of State Climatology OfficeViews of State Climatology Office

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1919thth Century Weather Data Century Weather Data