An Overview of California Climate Michael Anderson, State Climatologist.

An Overview of California Climate

Michael Anderson, State Climatologist

Talk Overview• California Climate

• Climate Signals

• Atmospheric Rivers

California

• 1340 miles of coastline (~75% of Pacific coast of conterminous US)

• 800 miles long• Average width 250 miles but crosses

550 miles of longitude (LA is east of Reno)• Land area of 163,696 square miles

– US Area is 3.79 million sq. miles– Rank 3rd behind Alaska and Texas

Elevation

• Max Elevation – Mt Whitney 14,491ft(Mt Shasta 14,161 ft)

• Min Elevation – Death Valley -282 ft

• Mt Whitney and Death Valley are only ~150 miles apart!

• Many islands in Sacramento/San Joaquin Delta lie ~20 feet below sea level

California’s topographyaffects our weather and climate

Comparing RegionsCA Climate TrackerDWR Hydrologic Regions

Climate Change Variables

• Temperature

• Precipitation

• Snowpack

• Annual and Seasonal Runoff

• Peak River Flows

• Mean Sea Level

Statewide 20th CenturyTemperature and Precipitation

WRCC’sCalifornia Climate Tracker

Differences from 1949-2005 average

Higher minimum temps since 1980

WRCC’sCalifornia Climate Tracker

Differences from 1949-2005 average

Dust Bowl Era

WRCC’sCalifornia Climate Tracker

11 year Mean

High variability, no trend

Spatial Variability

Annual Precipitation Map

Seasonal Variability

Inter-Annual Variability

Year to Year Precipitation Variability

Dettinger et al, 2011

Std Dev of Annual PrecipitationMean Annual Precipitation

California precipitation is uniquely variable

Higher values are higher variability

Precipitation and Runoff

Northern Sierra

Northern Sierra 8 Station Index

Annual Average: 50 inchesMaximum Year (1983): 88.5 inchesMinimum Year (1924): 17.1 inchesPeriod of Record 1921- Present

Average of:Mt. Shasta City QuincyShasta Dam Sierraville RSMineral Pacific HouseBrush Creek RS Blue Canyon

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep0

2

4

6

8

10

Monthly precipitation, inches

Lower elevation mountains

19211925

19291933

19371941

19451949

19531957

19611965

19691973

19771981

19851989

19931997

20012005

20092013

0

10

20

30

40

50

60

70

80

90

100

Long term avg

Never exceeded 80 in/yr prior to 1980

Water Year

Northern Sierra 8- Station Index Precipitation in Inches

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Monthly Average Runoff of Sacramento River System

1906-1955

1956-2007

Month

Ru

no

ff (

mil

lio

n a

cre

-ft)

Flood Control Operations

Runoff is a mixture of direct runoff and snowmeltIncreasing winter runoff, decreasing spring runoff

Water Supply Operations

Precipitation and Runoff

Southern Sierra

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep0

2

4

6

8

10

San Joaquin 5 Station Index

San Joaquin 5-Station Index

Annual Average: 40 inchesMaximum Year (1983) 77.4 inchesMinimum Year (1924) 14.8 inchesPeriod of Record 1949 - Present

Average of:Calaveras Big TreesHetch HetchyYosemite HQNorth Fork Ranger StationHuntington Lake

Monthly precipitation, inches

Higherelevation mountains

1905 1913 1921 1929 1937 1945 1953 1961 1969 1977 1985 1993 2001 2009 0

10

20

30

40

50

60

70

80

90

Long term avg

Water Year

San Joaquin 5 Station Index Precipitation in inches

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Monthly Average Runoff in San Joaquin River System

1901-19551956-2007

Month

Ru

no

ff (

mill

ion

acr

e-ft

)

Flood Control Operations Water Supply Operations

Runoff is dominated by snowmelt

Increasing winter runoff, decreasing spring runoff

Snow Pack

2011

2011

2011

SnowmeltApril-July Runoff

190619071908190919101911191219131914191519161917191819191920192119221923192419251926192719281929193019311932193319341935193619371938193919401941194219431944194519461947194819491950195119521953195419551956195719581959196019611962196319641965196619671968196919701971197219731974197519761977197819791980198119821983198419851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201120120%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

55%

60%

65%

70%

0%

10%

20%

30%

40%

50%

60%

70%

f(x) = − 0.000760538934698068 x + 0.428908406666395R² = 0.0813637228213251

Sacramento River (SBB+FTO+YRS+AMF Combined)April - July Runoff in percent of Water Year Runoff

Water Year (October 1 - September 30)

Pe

rce

nt

of

Wa

ter

Ye

ar

Ru

no

ff

Linear regression (least suqares) line showing historical trend

3-year running average

19011902190319041905190619071908190919101911191219131914191519161917191819191920192119221923192419251926192719281929193019311932193319341935193619371938193919401941194219431944194519461947194819491950195119521953195419551956195719581959196019611962196319641965196619671968196919701971197219731974197519761977197819791980198119821983198419851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201130%

35%

40%

45%

50%

55%

60%

65%

70%

75%

80%

85%

90%

30%

40%

50%

60%

70%

80%

90%

f(x) = − 0.000595473119359156 x + 0.709987377930854R² = 0.0559932020953621

San Joaquin River (SNS, TLG, MRC, and SJF Combined)April - July Runoff in percent of Water Year Runoff

Water Year (October 1 - September 30)

Pe

rce

nt

of

Wa

ter

Ye

ar

Ru

no

ff

Linear regression (least suqares) line showing historical trend 3-year running average

Peak Runoff

Feather River American River

Max Avg Min

American

98,000 27,000 3,200

Feather 150,000 43,000 5,000

Max Avg Min

American 166,000 39,000 1,500

Feather 245,000 55,000 3,000

Feather River American River

Max Avg Min

American

98,000 27,000 3,200

Feather 150,000 43,000 5,000

Max Avg Min

American 166,000 39,000 1,500

Feather 245,000 55,000 3,000

Average is higherExtremes are more extreme

Feather River American River

Climate Signals

El Niño Southern Oscillation (ENSO)

El Niño• Warm equatorial Pacific ocean• Flat Zonal Pacific Jet Stream• Enhanced storm track, flooding• 1983,1986-87, 1991-92, 1993,

1994,1997-98, 2002-3, 2009-10

La Niña• Cool equatorial Pacific ocean• Variable Loopy Pacific Jet Stream• 1985, 1995-96, 1999-2001,

2007-8, 2010-11, 2011-12

Low PressureBlocking

High Pressure

Warm

Extended Pacific Jet Stream& Amplified Storm Track

DryDry Wet

WarmVariable Pacific Jet Stream

Cool

Variable

Polar Jet

Stream

Polar Jet

Stream

Ocean Temperature Differences during El Niño and La Niña

http://www.climatewatch.noaa.gov/wp-content/uploads/2009/10/ENSO-states-viz.jpg

Warming in equatorial Pacific Cooling in equatorial Pacific

USAUSA

http://sealevel.jpl.nasa.gov/files/archive/science-elnino/el-nino-la-nina.jpg

Sea Surface Elevation Changes during El Niño and La Niña

El NiñoHigher ocean levels in east, lower in west

La Niña Lower ocean levels in east, higher in west

Change in ocean levels

USA

USA

When do we have El Niño/La Niña?• Develops April-June, strongest in December-February• Typically lasts 9-12 months, can last up to 2 years• Typically occurs every 2-7 years

Updated 11-19-14 http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml

Oceanic Niño Index (ONI) Blue La Niña Red El Niño

Strong El Niño97-98

2014 Warming Ocean (switch from negative to positive values)

Is this year an El Niño year?

Updated 11-19-14 http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

Most of the models predict weak El Niño conditions for winter and spring

Red bars: El Niño conditions Green bars: neutral conditions Blue bars: La Niña conditions

El NiñoNeutralLa Niña

Forecast

El NiñoNeutralLa Niña

Climatological Probability

Pacific Decadal Oscillation

Warm phase Cool phase

Anomaly patterns during warm and cool phases of PDOSea Surface Temp (colors), Sea Level Pressure (contours) & Surface Wind Stress (arrows)

http://jisao.washington.edu/pdo/

http://www.nwfsc.noaa.gov/research/divisions/fed/oeip/ca-pdo.cfm

Historical Pattern of PDO

Long term pattern of climate variability similar to ocean component of El Niño

20-30 years vs 6-18 months

Warm phase (positive) Cool phase (negative)

Atmospheric Rivers

Group ActivityGroup 1: Pacific Decadal Oscillation

Warm Phase Cool Phase

Han

ds U

p

Han

ds

Dow

n

Han

ds U

p

Han

ds

Dow

n

Group 2: El Niño Southern Oscillation

El Niño La Niña

Group 3: Madden Julian Oscillation

Group 4: Seasons

Group 5: ScientistsH

ands

Up

Han

ds

Dow

n

Han

ds U

p

Han

ds

Dow

n

Wet Season Dry Season

Wet phase Dry phase

Big Storm Conditions

Han

ds

Up

Han

ds

Up

Han

ds

Up

Han

ds

Up

Likely Drier Conditions

Han

ds

Dow

n

Han

ds

UpHan

ds

Dow

n

Han

ds

Dow

n

Count 20

Count 3

Count 2

Count 8

Ocean Atmosphere

Ocean/Atmosphere Geophysical

Take Home Points

• California has a Mediterranean Climate(warm dry summer, cool wet winter)

• Topography is important

• Lots of variability in space and time

Take Home Points

• Atmospheric Rivers important for floods and water supply

• Many processes in play to create a weather event recorded as obs of rain, snow, temperature

• Alignment of processes necessary for extreme events

Questions?

Email: [email protected]