1

Mike CrimminsClimate Science Extension Specialist Dept. of Soil, Water, & Env. Science &

Arizona Cooperative ExtensionThe University of Arizona

Mike CrimminsClimate Science Extension Specialist Dept. of Soil, Water, & Env. Science &

Arizona Cooperative ExtensionThe University of Arizona

Southwestern Climate: Past, present and future

Southwestern Climate: Past, present and future

Presentation Overview

• The global climate system• An overview of Arizona

climate • Why so much variability?• Climate change and Arizona

From: http://www.fsl.noaa.gov/visitors/education/climgraph/CG_Figure_10.gif.html

What is climate?Climatology: analysis of

long-term weather patterns over time or space

– The frequency of extreme events also important in climatic analyses (e.g. droughts & floods)

– Mean conditions AND variability

Global Energy Balance

From http://www.bom.gov.au

From http://www.climatechange.gc.ca

Global Circulations: Flows of Mass & Energy

Atmosphere

Ocean

From http://www.bom.gov.au

2

Background on AZ Climate

Annual Average Arizona Temperatures

Annual Average Arizona PrecipitationArizona Climograph

0

0.5

1

1.5

2

2.5

jan feb mar apr may jun jul aug sep oct nov dec

pre

cip

(in

.)

0

20

40

60

80

100

tem

p (

F)

Precip (in.) Temp (F)

Seasonal Distribution of Precipitation

Mean AnnualPrecip (in.)

Annual Avg.Temp (F)

Jan Dec

3 in.

•More winter precip in northern AZ•Stronger monsoon signal in southeast AZ (more summer precip)

(graphic from Sheppard, et al. 2000)

Annual Average Arizona Potential

Evapotranspirationhttp://southwest.library.arizona.edu/

3

Long-term Precipitation VariabilityAverage Daily Observations: Coolidge-AZMET

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

1 31 61 91 121 151 181 211 241 271 301 331 361

Day of Year

inch

es

0

10

20

30

40

50

60

70

80

90

100

deg

F

Ref ET (in) Total Precip (in) Avg Temp (F)

Annual Avg. Total Precip: 7.4 in.Annual Avg. Total ET: 77.6 in

Daily averages based on 1987-2007 period

Example Water Balance: Walnut Gulch, Arizona

http://www.tucson.ars.ag.gov/dap/field_sites.htm

Precipitation: 1000-1988

http://www.climas.arizona.edu/research/paleoclimate/product.html

Upper Gila – Annual Total Precipitation

http://www.cefa.dri.edu/Westmap/

Upper Gila – Summer Total Precipitation

http://www.cefa.dri.edu/Westmap/

Upper Gila – Winter Total Precipitation

http://www.cefa.dri.edu/Westmap/

4

0

5

10

15

20

25

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

Pre

cip

(in

)

Year

Total precip by season

OND

JAS

AMJ

JFM

6/26/2012

Bowie, AZ - NWS Coop Daily Precip Analysis

San Simon Watershed

010203040506070

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

Day

s

Total Wet Days (precip>0.04) per year

0

5

10

15

20

25

30

35

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

Day

s

Total Wet Days (precip>0.04) per season

JFM

AMJ

JAS

OND

Bowie, AZ - NWS Coop Daily Precip Analysis

Historic Streamflows

From USGS, http://pubs.usgs.gov/fs/2005/3081/

Southern AZ Upper Gila – Avg. Annual Temperature

http://www.cefa.dri.edu/Westmap/

Atmospheric Controls on Arizona Climate

Atmospheric Circulation and Arizona Climate

• Large-scale circulation patterns are an important determinant of local climate

• Arizona has a unique geographic position in northern hemisphere

• Circulation patterns are tied to global ocean sea surface temperatures

• Patterns can persist for years and even decades

5

Seasonality of Circulation Patterns

Global Circulations and Aridity

Shift of jet stream track towards Arizona

LL

DRY AIR

MOIST AIR

Winter Circulation Pattern

HH

HHMonsoon

circulation

HHWeak flow around expanded Bermuda sub-tropical

high-pressure systemDRY AIR

MOIST AIR

Summer Circulation Pattern

HH

North American Monsoon

Monsoon

Monsoon start dates for Tucson•Average start July 3rd

•Earliest start June 17 2000 •Latest start July 25 1987

Monsoon season rainfall (June 15th to September 30th)•Average monsoon season rainfall 6.06” •Driest monsoon season 1.59” in 1924 •Wettest monsoon season 13.84” in 1964

6

Upper Level Flow - May Upper Level Flow - June

Upper Level Flow - Julywesterly wind

easterly wind

Four CornersHigh Pressure

CO. River ValleyThermal Low

Core Monsoon Area(abundant tropical moisture,

frequentthunderstorm activity)

Mid-level moisturefrom Gulf of Mexico

Low-level moisturefrom Gulf of California

PACIFIC OCEAN

Mexico

TX

NM

CO

AZ

UTNV

CA

TX

KS

NE

GULF OFMEXICO

Conceptual diagram of key circulation features of the North American Monsoon System

Interannual Climate Variability

El Nino – Southern Oscillation

7

Dominant Circulation Pattern: La Nina Winter

ArizonaDrought

Dominant Circulation Pattern: El Nino Winter

Arizona ENSO Connection

19992000

2001

2002

2003

2004

2005

20062007

Pacific Decadal Oscillation

Period North Pacific SSTs

Southwest Winters

1920s-1940s Cold Wetter

1940s-1970s Warm Drier

1970s-20?? Cold Wetter

20??-???? Warm Drier?

Warm Cool

Surf. PressureAnomaly

(from Pagano 1999)

(from http://tao.atmos.washington.edu/pdo)

Pacific Decadal Oscillation (Nov-Mar)

-3

-2

-1

0

1

2

3

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PD

O in

dex

Climate Change Trends and patterns in

temp

IPCC 2007

8

Observed U.S. Climatic Trends

Courtesy of Noah Knowles, USGS

Trends in Nov-Mar Snowfall Fraction

More Rain, Less Snow More Snow, Less Rain

Proceedings of the National Academy of Sciences, 2005

Dev=2003-1989

What is going on and why?

From http://www.climatechange.gc.ca

Changes in greenhouse gases over

the past 10,000 years

IPCC 2007

9

Climate Change Attribution

•Earth is now radiating 0.85 W/m2 less energy than it is receiving•Imbalance and associated warming are consistent with GHG forcings•Components of natural variability (e.g. solar irradiance and volcanic aerosols) are small•More warming “in the pipeline”

Hansen et al. 2005Stott et al. (2000)

Natural Only

Observed

Natural vs. Anthropogenic Forcings

Where are we headed?

Precipitation Sensitivity to Warming Temperatures

Solomon et al. 2009

Temp Projections for Arizona

IPCC-AR4 18 model ensemble outputCourtesy of Jon Eischeid and Marty Hoerling, NOAA

Increasing Temps=Increasing Aridity?

Hoerling & Eischeid 2007

10

Implications for Arizona• Higher temperatures

– Higher evaporation and transpiration rates (increased water loss in reservoirs, faster drying of soils following precip events, more stress on vegetation)

– Less snow/more rain in winter; less snowpack for spring runoff, earlier pulse of precip/less water available in summer

– Longer growing seasons; more extreme events• Precipitation

– Projections are lower confidence – Higher temperatures on same precipitation variability:

more intense drought periods– Increasing variability more flooding with intervening

drought periods

Closing Points• Elevation, latitude, and ocean sea-surface

temperatures create a complex Arizona climate

• Different mechanisms create summer versus winter precipitation

• Lots of opportunity for variability (spatially and temporally)

• Climate change is real and a reason for concern in Arizona

Resources• Climate Assessment for the Southwest

(http://www.climas.arizona.edu/)• National Weather Service• (http://www.weather.gov)• Climate Prediction Center

(http://www.cpc.noaa.gov/)• Western Regional Climate Center

(http://wrcc.dri.edu/)• National Drought Monitor

(http://www.drought.unl.edu/dm/index.html)• Climate Science Applications Program

(http://cals.arizona.edu/climate)