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


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


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.


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?


© 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)

ADEQ SW Short Course 7 ADEQ SW Short Course © 2013 - The University of Arizona

Where does our precipitation come from?

Moisture from theGulf of MexicoGulf of California

E. Pacific Ocean

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Types of Precipitation


Convective

Frontal/synoptic

ADEQ SW Short Course 9

Daily Patterns – Sep. vs Feb.

ADEQ SW Short Course © 2013 - The University of Arizona 10rainlog.org

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


Annual variability of temp/precip - TUS

12weatherspark.com/history/31809/2012/Tucson-Arizona-United-States


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?



Orographic Pattern to SWE

www.nohrsc.noaa.gov/interactive/html/map.html

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Annual Patterns of Precipitation



Source: www-unix.oit.umass.edu

Orographic Precipitation: related to mixing ratio & lapse rate


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.


What causes extreme events?

What patterns do we see in Floods and Droughts?


Sources of excess runoff


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


Storm/Runoff Classification

ADEQ SW Short Course © 2013 - The University of Arizona 22Source: AHIS, Hirshbeck

Summer ConvectiveTropicalWinter Synoptic

Storm/Runoff Statistics


Tropical Frontal

Convective


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


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


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



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

© 2013 - The University of ArizonaADEQ SW Short Course 28

ADEQ SW Short Course © 2013 - The University of Arizona 29 ADEQ SW Short Course © 2013 - The University of Arizona 30http://droughtmonitor.unl.edu


Drought Monitor – historical


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

ADEQ SW Short Course © 2013 - The University of Arizona 33 ADEQ SW Short Course © 2013 - The University of Arizona

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.


Paleo climate indicators

How do we determine climate for time before we took measurements?



Dendrochronology - Tree Ring Basics

37

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


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


treeflow.info/upco/coloradoleesmeko.html

RMSE ~ 2.5 Maf

Upper Basin – persistent drought


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


Griffin et al., GRL (2013)

WYN2K: Weak relationship between cool and monsoon season events

ADEQ SW Short Course © 2013 - The University of Arizona 42http://www.swcarr.arizona.edu/chapter/5


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


Predicting Water Supplies

How predictable are our water supplies?How does uncertainty in precipitation affect water resources?


Where does our water supply come from?

A. SnowmeltB. GroundwaterC. Water reuseD. All of the above


Recent Water Supply Forecast Map


www.nwrfc.noaa.gov/westernwater

47http://wateroutlook.nwrfc.noaa.gov/ ADEQ SW Short Course © 2013 - The University of Arizona

Feb. Water Supply Outlook

48

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


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


www.climas.arizona.edu/sw-climate


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”

52


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”


http://www.esrl.noaa.gov/psd/people/klaus.wolter/MEI/#LaNina

WYN2K: ENSO has a ~2-4 year cycle

Relative Performance


http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html

WYN2K: ENSO predictions are poor beyond 6 months

Can you interpret this?


iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html


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


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


AZ Cooperative Extension


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


measuring rainfall precipitationweb.sahra.arizona.edu/education2/science/docs/adeq3... · how...

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