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 3 rd 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 topography affects our weather and climate

Comparing Regions CA Climate TrackerDWR Hydrologic Regions

Climate Change Variables Temperature Precipitation Snowpack Annual and Seasonal Runoff Peak River Flows Mean Sea Level

Statewide 20 th Century Temperature and Precipitation

WRCC’s California Climate Tracker Differences from average Higher minimum temps since 1980

WRCC’s California Climate Tracker Differences from average Dust Bowl Era

WRCC’s California 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 Precipitation Mean 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 inches Maximum Year (1983): 88.5 inches Minimum Year (1924): 17.1 inches Period of Record Present Average of: Mt. Shasta City Quincy Shasta Dam Sierraville RS Mineral Pacific House Brush Creek RS Blue Canyon Monthly precipitation, inches Lower elevation mountains

Long term avg Never exceeded 80 in/yr prior to 1980

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

Precipitation and Runoff Southern Sierra

San Joaquin 5-Station Index Annual Average: 40 inches Maximum Year (1983) 77.4 inches Minimum Year (1924) 14.8 inches Period of Record Present Average of: Calaveras Big Trees Hetch Hetchy Yosemite HQ North Fork Ranger Station Huntington Lake Monthly precipitation, inches Higher elevation mountains

Long term avg

Runoff is dominated by snowmelt Increasing winter runoff, decreasing spring runoff

Snow Pack

El Niño La Niña El NiñoLa Niña

2011

Snowmelt April-July Runoff

Peak Runoff

Feather RiverAmerican River

MaxAvgMin American 98,00027,0003,200 Feather150,00043,0005,000 MaxAvgMin American166,00039,0001,500 Feather245,00055,0003,000 Feather RiverAmerican River

MaxAvgMin American 98,00027,0003,200 Feather150,00043,0005,000 MaxAvgMin American166,00039,0001,500 Feather245,00055,0003,000 Average is higher Extremes are more extreme Feather RiverAmerican River

Climate Signals

El Niño Southern Oscillation (ENSO) El Niño Warm equatorial Pacific ocean Flat Zonal Pacific Jet Stream Enhanced storm track, flooding 1983, , , 1993, 1994, , , La Niña Cool equatorial Pacific ocean Variable Loopy Pacific Jet Stream 1985, , , , , Low Pressure Blocking High Pressure Warm Extended Pacific Jet Stream & Amplified Storm Track Dry Wet Warm Variable Pacific Jet Stream Cool Variable Polar Jet Stream Polar Jet Stream

Ocean Temperature Differences during El Niño and La Niña Warming in equatorial PacificCooling in equatorial Pacific USA

Sea Surface Elevation Changes during El Niño and La Niña El Niño Higher ocean levels in east, lower in west La Niña Lower ocean levels in east, higher in west Change in ocean levels 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 Oceanic Niño Index (ONI) Blue La Niña Red El Niño Strong El Niño 97-98

Is this year an El Niño year? El Niño Neutral La Niña Most models predict neutral conditions from summer 2013 will continue for fall El Niño Neutral La Niña Forecast Climatological Probability

Pacific Decadal Oscillation Anomaly patterns during warm and cool phases of PDO Sea Surface Temp (colors), Sea Level Pressure (contours) & Surface Wind Stress (arrows) research/divisions/fed/oeip/ ca-pdo.cfm Historical Pattern of PDO Long term pattern of climate variability similar to ocean component of El Niño years vs 6-18 months Warm phase (positive)Cool phase (negative)

Atmospheric Rivers

Weather Channel Dec 17, 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 Vapor Atmospheric 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 2008 Note 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 Bay March 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 occurs  Details 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 Activity Group 1: Pacific Decadal Oscillation Warm PhaseCool Phase Hands Up Hands Down Hands Up Hands Down Group 2: El Niño Southern Oscillation El NiñoLa Niña Group 3: Madden Julian Oscillation Group 4: Seasons Group 5: Scientists Hands Up Hands Down Hands Up Hands Down Wet SeasonDry SeasonWet phaseDry phase Big Storm Conditions Hands Up Likely Drier Conditions Hands Down Hands Up Hands Down Count 20 Count 3 Count 2 Count 8 Ocean Atmosphere Ocean/AtmosphereGeophysical

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?