Nolan DoeskenNolan DoeskenState Climatologist, Colorado Climate CenterState Climatologist, Colorado Climate Center

Atmospheric Science DepartmentAtmospheric Science DepartmentColorado State UniversityColorado State University

Presented at 17th Annual South Platte Forum, October 26, 2006, Longmont, Colorado

Prepared by Odie Bliss, Wendy Ryan and Daniel Denison

Living in the Past –What Does Colorado’s Historic

Weather Data Show Us?

Systematic weather data collection began in the South Platte Basin and in other parts

of Colorado in the early 1870s

Denver November 19Denver November 19--25, 187125, 1871

In the 1880s the Colorado legislature approved and funded

the “Colorado Meteorological

Association” to better monitor and document the climatic resources

of our young state.

In 1890 the USDA took over the responsibilities of climate

monitoring on a national level, and the first civilian weather service

was formed –the U.S. Weather Bureau

Colorado Weather Stations in 1890

Since then, the U.S. Weather Bureau/National Weather Service has faithfully maintained an oft taken for

granted network of weather stations in Colorado and across the country – the Cooperative Observer Network

Photo by Christopher Davey

From Kelly Redmond, WRCC

National Weather Service Cooperative Network

In recent years, many other organizations have gotten involved in weather measurements

» (show your slide of assorted weather stations by various orgs.)

The NWS stations remain the backbone network for long-term

climate monitoring

Colorado average annual precipitation map

What have we learned from nearly 120 years of continuous

climate monitoring in the South Platte Basin?

Winters are consistently colder than summers –☺

Average Monthly Temperatures (1971-2000) for Selected Stations in the South Platte

0

10

20

30

40

50

60

70

80

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonth

Tem

pera

ture

(deg

F)

Boulder Denver Sterling Evergreen Berthoud Pass

Temperatures are far more stable than precipitation. In fact most other

climatic elements (humidity, wind, sunshine and cloudiness, evaporation, etc.) are much more consistent from

one year to the next than precipitation.

Akron 4E Annual Precipitation Totals

5

10

15

20

25

30

1905

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2005

Prec

ipita

tion

(inch

es)

Akron 4E Average Mean Temperatures

35

40

45

50

55

60

1905

1910

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1925

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1935

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1945

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1995

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2005

Tem

pera

ture

(deg

F)

Precipitation varies by as much as 400% from a very dry year to a very wet year

Fort Collins Total Water Year Precipitation(1890 through 2006)

0

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15

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25

30

35

1890

1895

1900

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Month

Prec

ipita

tion

(inch

es)

Drought Visits Our Area Regularly

Photo by NRCS

Colorado Statewide Water Year (Oct-Sep) Precipitationfrom 1896 - 2006

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15

20

25

1895

1900

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2005

Year

Prec

ipita

tion

(inch

es)

Colorado Statewide Water Year Precipitation

Fraction of Colorado in Drought Based on 48 month SPI

(1890 - Sep 2006)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1890

1892

1895

1897

1900

1902

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1907

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2002

2005

Year

Frac

tion

(in p

erce

nt)

Confidently detecting climatic trends is much more challenging and

difficult than determining spatial

patterns, seasonal cycles, or year-to-year

variations

Denver (all 3 stations) Monthly Average Maximum and Minimum Temperatures

30

35

40

45

50

55

60

65

7018

70

1875

1880

1885

1890

1895

1900

1905

1910

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1930

1935

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1945

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2005

2010

Tem

pera

ture

(deg

F)

Denver City Tmax Denver WSFO Tmax DIA Tmax

Denver City Tmin Denver WSFO Tmin DIA Tmin

We can find many frustrating limitations to our climate records –

• Changing instrumentation,

• Aging weather observers,

• Changing environments around our weather stations,

• Changing weather station locations,

• Automation, etc.

Dillon Annual PrecipitationDillon Precipitation

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Prec

ipita

tion

(inch

es)

Fort Collins Winter TemperaturesFort Collins Water Year Average Temperatures

for Winter (Oct-Apr)

25

27

29

31

33

35

37

39

41

43

45

1890

1895

1900

1905

1910

1915

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1925

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2005

Year

Tem

pera

ture

(deg

ree

F)

Colorado Springs minus CheesmanTemperature Difference

Colorado Springs minus Cheesman Average Temperatures

-15

-10

-5

0

5

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20

25

1948

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1996

1998

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2002

2004

Tem

pera

ture

Diff

eren

ce (d

eg F

)

Colorado Springs AP-Cheesman MMNT Colorado Springs AP-Cheesman MMXT

Still, our climate records are more complete, consistent, and widespread than nearly all other forms of long-term environmental monitoring

(i.e. we shouldn’t whine).

Kassler Winter TemperaturesKassler Winter (DJF)

Average Maximum and Minimum Temperatures

0

10

20

30

40

50

60

1914

1917

1920

1923

1926

1929

1932

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1968

1971

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2001

2004

YEAR

Tem

pera

ture

(deg

F)

Winter Tmax Winter Tmin

Kassler Summer TemperaturesKassler Summer (JJA)

Average Maximum and Minimum Temperatures

40

50

60

70

80

90

100

1914

1917

1920

1923

1926

1929

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1935

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1941

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1962

1965

1968

1971

1974

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1980

1983

1986

1989

1992

1995

1998

2001

2004

YEAR

Tem

pera

ture

(deg

F)

Summer Tmax Summer Tmin

If climate is changing (man caused or otherwise), it will still be a long time before we can tell if

our precipitation patterns are changing.

Recently, upward trends in seasonal temperatures have

become noticeable in parts of Colorado

That may be significant for water users/planners whether or not

precipitation is changing

Grand Lake, CO Winter Daily Minimum Temperature Distribution (5 degree bins)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

-45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40Temperature Bin

Freq

uenc

y

Frequency 1950-1961Frequency 1961-1972Frequency 1972-1983Frequency 1983-1994Frequency 1994-2005

Grand Lake, CO Spring Daily Maximum Temperature Distribution (5 degree bins)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 10 20 30 40 50 60 70 80 90Temperature bin

Freq

uenc

y

Frequency 1951-1961Frequency 1962-1972Frequency 1973-1983Frequency 1984-1994Frequency 1995-2005

What should we do??

Always plan for drought!Fraction of Colorado in Drought

Based on 48 month SPI(1890 - Sep 2006)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1890

1892

1895

1897

1900

1902

1905

1907

1910

1912

1915

1917

1920

1922

1925

1927

1930

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1995

1997

2000

2002

2005

Year

Frac

tion

(in p

erce

nt)

And have your rain gauge ready

CoCoRaHS Statewide Precipitation October 21, 2006

CoCoRaHSBoulder County

PrecipitationOctober 21, 2006

If you are a chronic weather watcher or water worrier (or warrior) and you

aren’t already a part of CoCoRaHS,

please see me at the break or at lunch.

For More Information, Visit theCoCoRaHS Web Site

Support for this project provided by NSF Informal Science Education Program, NOAA Environmental Literacy Programandmany local charter sponsors.

http://www.cocorahs.org

Colorado Climate CenterData and Power Point Presentations available for downloading

http://ccc.atmos.colostate.edu