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
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
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
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
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
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: [email protected]