Measuring rainfall Precipitationweb.sahra.arizona.edu/education2/science/docs/ADEQ3... · How...
Transcript of Measuring rainfall Precipitationweb.sahra.arizona.edu/education2/science/docs/ADEQ3... · How...
Precipitation
ADEQ SW Short CourseJune 13, 2013Phoenix, AZ
ADEQ SW Short Course © 2013 - The University of Arizona 1
CLIMATE is what you expect, WEATHER is what you get – R.A. Heinlein
Outline
• Measuring rainfall• Patterns of precipitation in time and space• Predicting precipitation• Patterns related to extreme events (floods &
drought)• Paleo-climate indicators• Climate patterns (ENSO)• Sources of information about precipitation and
climate
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Bottom line: one-page summary
• Precipitation varies seasonally depending on fetch and storm type.
• Precipitation varies by location, mainly due to orographic effects.
• Tropical storms give rise to the biggest floods.• Extended periods of drought are normal in S, as
evidenced by tree rings.• Rocky Mt snowpack is critical to our water supply• El Nino “teleconnections” can result in wetter
winters for southern AZ
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How would you describe precipitation patterns in your area?
A. It only rains much in the summer.
B. It only rains much in the winter.
C. Rain storms during Jul-Aug or Dec-Feb are fairly similar.
D. Rain storms during Jul-Aug or Dec-Feb are quite different.
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How important is rainfall?
• 640 ac/mi2
• => 89.6 Mac
• Precip ~ 1 ft/yr• => 89.6 Maf• Where does it go?• Runoff ~ 1.8 Maf• => Evap. ~ 98 %ADEQ SW Short Course © 2013 - The University of Arizona 5
AZ ~ 140,000 mi2
How does precipitation vary in time and space?
What areas get the most precipitation and why?Why are summer storms different from winter storms?
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© 2013 - The University of Arizona
High Variability in Space and TimePrecipitation influenced by rough mountains.
Winter: Large scale storms fromthe Pacific Ocean. Important for watersupply and snow.
Summer:Complex convectivestorms, very heterogeneous, intense.High evaporation.
Sources of Precipitation% Precipitation in Winter (Oct-Mar)
% Precipitation in Summer (July & Aug)
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Where does our precipitation come from?
Moisture from theGulf of MexicoGulf of California
E. Pacific Ocean
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Types of Precipitation
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Convective
Frontal/synoptic
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Daily Patterns – Sep. vs Feb.
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ADEQ SW Short Course © 2013 - The University of Arizona
Annual variability of temp/precip
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www.wrh.noaa.gov/images/twc/cliplot/KTUS2012plot.png
ADEQ SW Short Course © 2013 - The University of Arizona
Annual variability of temp/precip - TUS
12weatherspark.com/history/31809/2012/Tucson-Arizona-United-States
ADEQ SW Short Course © 2013 - The University of Arizona
Annual variability of temp/precip - PHX
13weatherspark.com/history/31259/2012/Phoenix-Arizona-United-States
© 2013 - The University of Arizonahttp://www.wrcc.dri.edu/pcpn/westus_precip.gif
What factors control precipitation in the SW?
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ADEQ SW Short Course © 2013 - The University of Arizona
Orographic Pattern to SWE
www.nohrsc.noaa.gov/interactive/html/map.html
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Annual Patterns of Precipitation
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© 2013 - The University of Arizona
Source: www-unix.oit.umass.edu
Orographic Precipitation: related to mixing ratio & lapse rate
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Saturated Mixing Ratio
Which is the best explanation of orographic precipitation?
A. Precipitation that occurs where moist oceanic air is forced over coastal ranges.
B. The increased likelihood that higher areas will receive more precipitation.
C. Precipitation that occurs where moist air cools and condenses as it is forced to rise over higher elevations.
D. Precipitation that happens over mountains.
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What causes extreme events?
What patterns do we see in Floods and Droughts?
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Sources of excess runoff
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Unusual supplies of moisture
• Stationary storm tracks• Tropical storms / Hurricanes• Rain on snow / Rapid melt• Saturated ground
Factors Affecting Flooding
• Persistence and intensity of precipitation• Soil moisture conditions• Surface cover – forested to bare• Permeability – sandy/tilled to compacted
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Storm/Runoff Classification
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Summer ConvectiveTropicalWinter Synoptic
Storm/Runoff Statistics
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Tropical Frontal
Convective
© 2013 - The University of Arizona
Tropical Storm & Monsoon-related floodsOct 1-2, 1983
STORM PRECIPITATION TOTALS:Tucson: 6.40"
PEAK FLOWS:San Pedro R near Tombstone: 13,600 cfsSan Pedro R @ Winkelman: 135,000 cfsGila R @ Kelvin: 100,000 cfs (10/02/83)Santa Cruz R @ Tucson: 52,700 cfsRillito Creek near Tucson: 29,700 cfsSanta Cruz R @ Cortaro: 65,000 cfs
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Phoenix/Salt – Historic Floods• 1891 (feb) – 300,000 cfs• 1905 (nov) – photo =>• 1916 (jan) 100,000 cfs• 1937 (feb) 88,000 cfs• 1941 (mar) 117,000 cfs• 1952 (jan) 111,000 cfs• 1965 (dec) 69,000 cfs; all bridges damaged• 1967 (aug) “Katrina”• 1970 (sep) “Norma”• 1972 (oct) “Joanne”; 70,000cfs• 1978 (mar) 89,500 cfs; 122,000 cfs• 1978 (nov) 140,000 cfs• 1979 (jan) 96,000 cfs; 54,000 cfs• 1980 (jan) 170,000 cfs; 99,000 cfs; 64,000 cfs; 11/13 bridges damaged• 1983 (oct) “Octave” ; 60,000 cfs; 33,000 cfs• 1993 (jan) El Nino; 143,000 cfs; 34,500 cfs• 2005 (all summer) 2-3” events; 46,500 cfs• 2008 (jan) 81,300 cfs• 2010 (jan) 1-5”; 88,300 cfs; 32,000 cfs
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USGS 09502000 SALT RIVER BLW STEWART MOUNTAIN DAM, AZ
USGS 09498500 SALT RIVER NEAR ROOSEVELT, AZ
Black cfs – PHOENIX est?
Factors Affecting Drought Severity & Impact
• Dryness• Warmth• Persistence • Soil moisture conditions• Availability of alternative
water supplies• Ability to fallow land or
curtail use
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ADEQ SW Short Course © 2013 - The University of Arizona
PDSI• The Palmer Drought Severity Index responds to abnormally wet(+) or dry(-)weather conditions.
• The index is a sum of the current moisture anomaly and a portion of the previous index to include the effect of the duration of the drought or wet spell.
• The moisture anomaly is the product of a climate weighting factor and the moisture departure.
• It is slow to detect fast-emerging droughts, and does not reflect snowpack.
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Drought Indicators
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ADEQ SW Short Course © 2013 - The University of Arizona 29 ADEQ SW Short Course © 2013 - The University of Arizona 30http://droughtmonitor.unl.edu
© 2013 - The University of Arizona
Drought Monitor – historical
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droughtmonitor.unl.edu/archive.html http://www.youtube.com/watch?v=_1vLaEVmG34&feature=player_embedded
ADEQ SW Short Course © 2013 - The University of Arizona 32http://cals.arizona.edu/climate/misc/spi/spi_contour.html
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SW Climate Outlook
http://www.climas.arizona.edu/outlooks/swcol, accessed 5/2013
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Which one of the following best describes Drought Monitor Maps?
A. They can change rapidly, depending upon recent precipitation.
B. They incorporate local soil & precip. conditions.C. The index is reset every winter.D. Correspond with maps of shallow soil moisture.
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Paleo climate indicators
How do we determine climate for time before we took measurements?
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ADEQ SW Short Course © 2013 - The University of Arizona
Dendrochronology - Tree Ring Basics
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Tree ring width based on:• soil moisture conditions• soil and air temperatures • sunshine
Crossdating:• matching ring-growth
across many samples• allows construction of
continuous record of growing conditions from discontinuous sample of tree rings.
Skeleton Plots:• adjustment for
local variation
www.ltrr.arizona.edu/treerings.html
Earlywood
Latewood
ADEQ SW Short Course © 2013 - The University of Arizona
Tree-ring and Streamflow Correlation
0
500
1000
1500
2000
2500
1900 1920 1940 1960 1980 2000
Dis
char
ge (c
fs)
Year
Annual Avg Flow for the Gila River @ Coolidge Dam
•Tree-rings correlate to certain climate events
•Especially El Niño & La Niña events
•Significance: 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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Colorado River @ Lee’s Ferry
Woodhouse et al. (2006)
Calibration, Validation, Reconstruction
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treeflow.info/upco/coloradoleesmeko.html
RMSE ~ 2.5 Maf
Upper Basin – persistent drought
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Persistent drought (two or more years) in regional flow reconstructions, 1685–1987. Values are shown only for years with two or more values consecutively below the median.(Woodhouse & Lukas, Climate Change, 2006)
WYN2K: Persistent drought is a normal and
cyclic characteristic of the Southwest
Monsoon Predictability
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Griffin et al., GRL (2013)
WYN2K: Weak relationship between cool and monsoon season events
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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.”
Dry Times Ahead(Overpeck and Udall, Science 25 June 2010, V.328(5986) pp. 1642-1643)
• Reduced late season snowpack• Drying faster/more than climate
change models indicate• Colo. River flow decrease 20%
by 2050?• Chance of loss of Powell/Mead
storage now 3 in 10
• Recommendation:– Learn to live with less– Climate change adaptation
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Predicting Water Supplies
How predictable are our water supplies?How does uncertainty in precipitation affect water resources?
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Where does our water supply come from?
A. SnowmeltB. GroundwaterC. Water reuseD. All of the above
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Recent Water Supply Forecast Map
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www.nwrfc.noaa.gov/westernwater
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Feb. Water Supply Outlook
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2008 2013
www.cbrfc.noaa.gov/wsup/wsup.cgi
ADEQ SW Short Course © 2013 - The University of Arizonahttp://www.hydro.washington.edu/forecast/westwide/
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Impact of Climate Change
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Likely changes:• Warmer temperatures• Less snowpack?• Earlier runoff• Increased water demand
• Longer growing season• More ET; less SM
• Warmer water WQ issues
www.swcarr.arizona.edu/chapter/5
Longer-term climate patterns that might lead to greater predictability
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www.climas.arizona.edu/sw-climate
ADEQ SW Short Course © 2013 - The University of Arizona
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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ADEQ SW Short Course © 2013 - The University of Arizona
http://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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http://www.esrl.noaa.gov/psd/people/klaus.wolter/MEI/#LaNina
WYN2K: ENSO has a ~2-4 year cycle
Relative Performance
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http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html
WYN2K: ENSO predictions are poor beyond 6 months
Can you interpret this?
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iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html
ADEQ SW Short Course © 2013 - The University of Arizona
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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Precipitation during El Nino Winters
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see also: Effect of OLR, Climate, 2012journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00097.1
www.southwestclimatechange.org/figures/AZ_NM_elnino
What is our current predictability of ENSO?
A. Month to month.B. 6 months.C. 2-4 yearsD. Decadal
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AZ Cooperative Extension
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cals.arizona.edu/climate
Bottom line: one-page summary
• Precipitation varies seasonally depending on fetch and storm type.
• Precipitation varies by location, mainly due to orographic effects.
• Tropical storms give rise to the biggest floods.• Extended periods of drought are normal in S, as
evidenced by tree rings.• Rocky Mt snowpack is critical to our water supply• El Nino “teleconnections” can result in wetter
winters for southern AZ
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