An Overview of California Climate

Michael Anderson, State Climatologist[Presented by Michelle Selmon, Senior Environmental Scientist]

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

http://www.prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/tmin/Normals/us_tmin_1971_2000.14.png&year=1971_2000&vartype=tmin&month=14&status=final&zoom=yes

http://www.prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/tmax/Normals/us_tmax_1971_2000.14.png&year=1971_2000&vartype=tmax&month=14&status=final&zoom=yes

Annual Precipitation Map

Seasonal Variability

http://www.prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/tmin/Normals/us_tmin_1971_2000.08.png&year=1971_2000&vartype=tmin&month=08&status=final&zoom=yes

http://www.prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/tmax/Normals/us_tmax_1971_2000.08.png&year=1971_2000&vartype=tmax&month=08&status=final&zoom=yes

http://www.prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/tmin/Normals/us_tmin_1971_2000.12.png&year=1971_2000&vartype=tmin&month=12&status=final&zoom=yes

http://www.prism.oregonstate.edu/products/viewer.phtml?file=/pub/prism/us_30s/graphics/tmax/Normals/us_tmax_1971_2000.12.png&year=1971_2000&vartype=tmax&month=12&status=final&zoom=yes

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

1921

1922

1923

1924

1925

1926

1927

1928

1929

1930

1931

1932

1933

1934

1935

1936

1937

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1989

1990

1991

1992

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1998

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2002

2003

2004

2005

2006

2007

2008

0

10

20

30

40

50

60

70

80

90

100

Northern Sierra 8-Station Precipitation Index

Water Year

Pre

cip

ita

tio

n (

Inc

he

s)

Long term avg

Never exceeded 80 in/yr prior to 1980

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)

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

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

1949

1950

1951

1952

1953

1954

1955

1956

1957

1958

1959

1960

1961

1962

1963

1964

1965

1966

1967

1968

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1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

0102030405060708090

San Joaquin 5-Station Index

Long term avg

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

)

Runoff is dominated by snowmelt

Increasing winter runoff, decreasing spring runoff

Snow Pack

1950

1952

1954

1956

1958

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

0

50

100

150

200

250

107

63

237

97105

66

135

70

171

626360

152

45

66

97

83

134

70

224

67

114

54

148

117

149

37

25

152

104

127

69

130

227

79

98

122

59

29

80

45

83

60

157

52

182

99

82

158

109100

62

93

66

83

137

125

39

102

83

104

171

April 1 Snowpack Water ContentStatewide Percent of AverageEl Niño

El Niño El Niño

El Niño

El Niño

El NiñoEl Niño La Niña

La Niña

La NiñaEl Niño La Niña

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) = − 0.000760538934698067 x + 0.428908406666395R² = 0.0813637228213249

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 = 0.0559932020953617

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

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

Is this year an El Niño year?

http://iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html

El NiñoNeutralLa Niña

Most models predict neutral conditions from summer 2013 will continue for fall

El NiñoNeutralLa Niña

Forecast

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

Atmospheric Rivers

Weather Channel Dec 17, 2010 http://www.weather.com/blog/weather/8_23599.html

• Plume or “fire hose” of tropical moisture

• Heavy precipitation and possibly flooding

aka Pineapple Express

Pineapple Express

Hawaii

Satellite View

Forecast

CA

Where is the storm?Where is the impact?

Satellite Observation of Water VaporAtmospheric River

North America

GOES IR image of major West Coast storm• Time = 0030 UTC 5 January 2008• Low pressure center is off WA coast

The Storm of 4-5 Jan 2008Note that major impacts were focused >500 miles south of the Low pressure center in this storm.

This differs significantly from hurricanes, but the impacts are enormous and spread over a large area

L

~500 miles

Atmospheric river

7-13 in rain

6-10 ft snow

Many major impacts are associated with the landfall of the “atmospheric river” element of the storm, the precise characteristics of which are not operationally monitored offshore or onshore.

32 ft waves

Atmospheric Rivers are not just flood producers.

They are a key part of the water supply system

CAT 3 is > 30 cm (12 in) in 3 days

NOTE: Expanded color bar, but more sites still qualify

West coast precipitation totals during atmospheric river events can rival those from hurricanes

Number of Historical Storms with 3 Days of Precipitation of 12 inches or more

Just a few storms each year are the core of California’s water supplies

Storms and California Water Supply

Dettinger et al, 2011

Atmospheric River Observation at Bodega BayMarch 2013

RASS (radio acoustic sounding system)

Building RASS (radio acoustic sounding system) Completed Observation Site

Antenna array to measure wind speed

56

Hydro-Meterological Testbed HMT

Topography Matters

When atmospheric rivers strike coastal mountains (Ralph et al. 2003)Air ascends coastal mountains, water vapor condenses, heavy rainfall occursDetails of the atmospheric river determine which watersheds flood

Complications: Rain shadowing

Record flooding

Modest flooding

Storm Track changes

Flooding & water supply

MJO/Tropical Convection ENSO

Key Phenomena Affecting California Water Supply/Flooding:

Atmospheric

River

Easterly Wave

Cyclogensis

L

The most extreme CA storm would result from a rare alignment of key processes

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 are in play to create a weather event recorded as observation of rain, snow, temperature

• Alignment of processes necessary for extreme events

Questions?

Email: manderso@water.ca.gov