Decadal Signals In Precipitation

Slide 1: The prominence of decadal variability in North American precipitation S c ott St. G eorge Geological Survey of Canada Toby A ult University of Arizona

Slide 3: Greg McCabe, Michael Palecki, and Julio Betancourt, 2004: Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States PNAS 12, 4136 - 4141

Slide 4: Here be decadal variability Decadal variability in precipitation or drought as a signal detection problem Terrestrial climate records often processed to emphasize D2M timescales4

Slide 5: Does it matter at the regional scale? 5

Slide 6: 1920 1940 1960 1980 2000 Decadal variance 30% Decadal variance 5% 1920 1940 1960 1980 2000

Slide 7: Where is decadal variability in precipitation strong?

Slide 8: Dan Cayan, Michael Dettinger, Henry Diaz, and Nick Graham,1998: Decadal variability of precipitation over western North America. Journal of Climate 11, 3148-3166

Slide 9: Methods Photo: Christos_m2001

Slide 10: PDSI Temperature Precipitation Streamflow Storms Rain/snow

Slide 11: Gridded (0.5 deg) monthly precipitation, Climate Research Unit, University of East Anglia Period of record: 1901 - 2002

Slide 12: Decadal variability Decadal variabil Decadal varia Decadal v

Slide 15: Noise Interannual Trend Multidecadal Decadal

Slide 17: What did we find? Photo: futureshape

Slide 18: Slides missing* * Thank goodness

Slide 19: Winter decadal 0% 10% 20% 30% variance

Slide 20: Autumn decadal 0% 10% 20% 30% variance

Slide 21: Annual multidecadal 0% 10% 20% 30% variance

Slide 22: Northern California precipitation

Slide 23: Northern California precipitation Decadal variance = ~30 percent

Slide 24: D2M ‘hotspots’

Slide 25: “Decadal-scale fluctuations are crucial because they control water supplies, affect biota, and may modulate higher-frequency events such as floods and drought.” Dan Cayan and colleagues [1998]

Slide 26: Decadal hotspot - Oregon/California

Slide 27: Northern California

Slide 28: Sacramento River Photo: Patty Colmer

Slide 29: Northern California

Slide 30: Northern California

Slide 31: Photo: California Department of Water Resources Levee break, Sacramento basin

Slide 32: 1915 levee break Photo: California Department of Public Works Courtesy Joan Florsheim

Slide 33: Northern California

Slide 34: Northern California

Slide 35: Decadal hotspot - Minnesota

Slide 36: Minnesota

Slide 37: Mississippi River at Minneapolis Photo: Mulad

Slide 38: Minnesota

Slide 39: Minnesota

Slide 40: Minnesota

Slide 41: Mech et al. (1987): Does high snow over consecutive winters have a cumulative, negative, effect on the viability of moose offspring?

Slide 42: Minnesota

Slide 43: Minnesota

Slide 44: Minnesota

Slide 45: Associations with major climate modes

Slide 46: It’s complicated. 46

Slide 47: Winter precipitation and the PDO

Slide 48: Winter precipitation and the PDO

Slide 49: Three main points 49

Slide 50: location and seasonality make a big difference 50

Slide 51: D2M propagates into hydrology* and ecology** * clearly ** maybe 51

Slide 52: Is it a coincidence that D2M variability is strongest in the ENSO-PDO null? 52

Slide 53: Thank you Julio Betancourt Dave Meko Julia Cole Joellen Russell Susan Pullan Mike Wallace Mike Mann Connie Woodhouse Support Manitoba Hydro Natural Resources Canada National Science Foundation

Slide 54: S co t t St. G e o r g e Toby Au lt Geological Survey of Canada University of Arizona sstgeorg@nrcan.gc.ca tault@email.arizona.edu