weather & climate - sahraweb.sahra.arizona.edu/.../lesson7/hwr203climate_main.pdf · how do we...
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Arizona Water Issues © 2012 - The University of Arizona
Weather & Climate
CLIMATE is what you ______ WEATHER is what you ___– R.A. Heinlein
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Arizona Water Issues © 2012 - The University of Arizona
How do we determine climate?
• Temperature• Precipitation• Wind, Humidity, ….• …… over many years• Hydrologists focus on streamflow!
• Most important features: – Variability & Predictability
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Tucson Climate Pattern
http://www.wrcc.dri.edu/summary/climsmaz.html3
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Winter:• Large scale, homogenous storms from thePacific Ocean
• Important for water supply and snow
Summer:• Complex convective storms from the Gulf of Mexico
• Small scale, heterogeneous, intense and short-lived storms
• High evaporation
Regional Seasonal Climatic Patterns% Precipitation in Winter (Oct-Mar)
% Precipitation in Summer (July & Aug)
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Annual variability of temp/precip
http://www.wrh.noaa.gov/twc/climate/seazDM.php5
www.wrh.noaa.gov/climate/temp_graphs.php?wfo=twc
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Annual variability of temp/precip
http://www.wrh.noaa.gov/twc/climate/seazDM.php6
www.wrh.noaa.gov/climate/temp_graphs.php?wfo=twc
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Arizona Water Issues © 2012 - The University of Arizona
Annual variability of temp/precip
http://www.wrh.noaa.gov/twc/climate/seazDM.php7
www.wrh.noaa.gov/climate/temp_graphs.php?wfo=twc
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Arizona Water Issues © 2012 - The University of Arizona
http://www.wrcc.dri.edu/pcpn/westus_precip.gif
Remember-What factors control precipitation in the SW?
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2010 -- SWE Variability -- 2006
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Hydrologic events affected by climatic fluctuations
Timing of snowmelt runoff
Quantity of baseflow
Occurrence of floods
Duration and extent of drought10
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MAJOR SOURCES OF VARIABILITY
Can we predict next year’s water supply?
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What are El Niño & La Niña events?
• Changes(+/-) in normal sea surface temp. (>0.5°C)
Eastern Pacific:• El Niño: increase (+), warmer water temperature• La Niña: decrease (-), cooler water temperature
“Watch Areas”
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Arizona Water Issues © 2012 - The University of Arizonahttp://http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/ensocycle.shtml
Pacific sea surface temperatures along the equator tend to oscillate between warm and cold along the equator every three to seven years.
This oscillation is called the El Nino-Southern Oscillation (ENSO).
El Niño episodes (also called Pacific warm episodes or ENSO) and La Niña episodes (also called Pacific cold episodes) represent opposite extremes of the ENSO cycle.
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Nice ENSO educational resources: http://www.srh.noaa.gov/srh/jetstream/tropics/enso.htm
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http://www.srh.noaa.gov/srh/jetstream/tropics/enso_patterns.htm
El Nino – Weak Walker Circ. La Nina – Strong Walker Circ.
coolerwarmer
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http://www.esrl.noaa.gov/psd/people/klaus.wolter/MEI/#LaNina
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© 2012 - The University of Arizona
http://www.worldatlas.com/webimage/countrys/islands/pacifics/tahiti.gif
http://www.hplgroup.com/img/map_darwin.gif
www.asturi.com/pages/ galleries.html/tahiti_moorea_map.gif
The Southern Oscillation Index (SOI) is one measure of the large-scale fluctuations in air pressure occurring between the western and eastern tropical Pacific (i.e., the state of the Southern Oscillation) during El Niño and La Niña episodes.
Traditionally, this index has been calculated based on the differences in air pressure anomaly between Tahiti and Darwin, Australia.
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/soi.htmlArizona Water Issues 16
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THE SOUTHERN OSCILLATION INDEX (SOI)
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/soi.shtml
The Southern Oscillation Index (SOI) is one measure of the large-scale fluctuations in air pressure occurring between the western and eastern tropical Pacific (i.e., the state of the Southern Oscillation) during El Niño and La Niña episodes.
ENSO cycle has an average period of about four years, although in the historical record the period has varied between two and seven years.
El Niño
El Niño
17www.cpc.ncep.noaa.gov/data/indices/
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PDO
The "Pacific Decadal Oscillation" (PDO) is a long-lived El Niño-like pattern of Pacific climate variability. Causes for the PDO are not currently known.Two main characteristics distinguish PDO from ENSO: First, 20th century PDO "events" persisted for 20-to-30 years, while typical ENSO events persisted for 6 to 18 months; Second, the climatic fingerprints of the PDO are most visible in the North Pacific/North American sector, while secondary signatures exist in the tropics -the opposite is true for ENSO.
warm phase cool phase
Arizona Water Issues 18
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Pacific Decadal Oscillations
jisao.washington.edu/pdo
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ENSO Forecast - Current
Arizona Water Issues © 2012 - The University of Arizona 20iri.columbia.edu/climate/ENSO/currentinfo/
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ENSO Forecast
Arizona Water Issues © 2012 - The University of Arizona 21iri.columbia.edu/climate/ENSO/currentinfo/
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Relative Performance
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http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html
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Current conditions – Another strong El Nino?
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http://earthobservatory.nasa.gov/IOTD
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Can you interpret this?
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iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html
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CPC Ocean Temp. Forecast
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www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/
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Arizona Water Issues © 2012 - The University of Arizonahttp://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/enso_cycle.shtml
El Niño = Wet in Southwest US
La Niña = Dry in Southwest US
Warm winter storms are more common during El Nino
Below average flows in the CR are more common during La Nina
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“Tele – connections”
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Teleconnections
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Teleconnections
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REGIONAL EVIDENCE OF TELECONNECTIONS
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Dry period with weak El Ninoand strong La Nina events
Strong El Nino events thatproduced wet winters andhigh flow in Arizona
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Effect of ENSO on Winter Precip. in AZ
All EL NINO Years (1935-97)
Gila River @ Calva Daily Winter Streamflow (cfs)
All LA NINA Years (1935-97)
Climate variability: spatial, interannual, regimes (decadal), climate change
Credit: Tom Pagano
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Annual State of the Climate1895-2009
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http://www.ncdc.noaa.gov/oa/climate/research/2008/ann/ann08.html
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How important is predictability?
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Impacts of Climatic Variability - NW
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http://cses.washington.edu/cig/pnwc/clvariability.shtml
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How important is predictability?
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Whisker plots
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PALEO RECORDS
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Climate Variability
Global warming or Global change?37
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How do we determine climate for time before we took measurements?
• Tree-ring records• How do these work?• Tree ring width based on:
– soil and air temperatures – soil moisture conditions– sunshine– wind
• The factors change based on climate
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Tree-ring and streamflow correlation
Annual Average Flow for the Gila River below Coolidge Dam
0500
1000150020002500
1900 1920 1940 1960 1980 2000
Year
Dis
char
ge (c
fs)
•Tree-rings correlate to certain climate events
•Especially El Niño & La Niña events
•Tree-rings have a longer period of record than most streamflow & precipitation data sets
1500___1600___1700___1800___1900___2000
????????????????????????????1900___2000
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CR at Lee’s Ferry
Adjusted for:• Water year vs. calendar year• 0.29 Maf bias in dam inflows• Glen Canyon Dam Construction• Consumptive users were kept in
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Observed/Estimated CR flow data
Meko, LTRR, Presentation to CDWR, 6/04http://pubs.usgs.gov/fs/2004/3062/41
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Tree ring dendro-hydrology:Fact: We are in a historic drought
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Note 1920’s flow was historic high
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Eos, Vol. 89, No. 9, 26 February 2008MacDonald, UCLA
“Taken together, climatological and paleo-climatological evidence does not provideany reason to conclude that events such asthe early 21st-century drought could notpersist longer than the 5- to 8-year durationof historical droughts of the twentieth century.Prolonged episodes of aridity persistingfor a decade or more are apparent in manypaleohydrological records, and conditionsin the Pacific appear to have played a keyrole in these episodes.”
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Variability at 2 scales; Reconstructed flow
Arizona Water Issues © 2012 - The University of Arizona 45CRB Water Mgmt, NAS, 2/07
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Things to think about• How to illustrate project city climate and what
factors affect it?• How does precipitation vary in time and
space?– What areas get the most precipitation and why?– Why are summer storms different from winter
storms?– What causes extreme events? Are they
predictable?• How does uncertainty in precipitation affect
water resources?• What climate factors are of critical
importance to Arizona and the southwest?46
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How will climate change affect AZ?
Arizona Water Issues © 2012 - The University of Arizona 47
From: Climate Change and Natural Resources in Pima County, 2010
Hotter & Drier
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Declining Sierra Snowpack
Arizona Water Issues © 2012 - The University of Arizona 48
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