border climate summary - welcome | climas · university of arizona the monsoon is a major component...

Tree Rings and the Monsoon in the Southwestern U.S.

Border Climate Summary

The information in this packet is available on the web: http://climas.arizona.edu/forecasts/border/summary.html

Resumen del Clima de la FronteraIssued: February 18, 2010

1 Tree-RingsandtheMonsoonintheSouthwesternU.S.

3 Alookbackatthe2009summermonsoon

RecentConditions6 Temperature7 Precipitation8 NorthAmericanDroughtMonitor9 SonoranReservoirLevels

Forecasts10 StreamflowForecast11 PrecipitationForecast12 ENSO

Table of Contents:

continued on page 4

ByDanielGriffin,SchoolofGe-ographyandDevelopmentandTheLaboratoryofTree-RingResearch,UniversityofArizona

ThemonsoonisamajorcomponentofsouthwesternNorthAmerica’sclimateregimeandarguablyoneofthemostanticipatedregionalclimateeventsoftheyear,deliveringvaryingdosesoflife-givingrainstotheU.S.-Mexicoborderre-gioneachsummer.Onaverage,themon-soonbringsthree-fourthsofnorthwesternMexico’sannualrainfallanduptohalfoftheannualrainintheU.S.Southwest.

Variabilityinmonsoonrainfallintimeandlocationincreasesnorthwardwithdistancefromthe“coreregion”inwest-ernandnorthwesternMexicoandisnotablydramaticalongtheborderandintothesouthwesternU.S.Theseyear-to-yearchangesinfluenceecosystems,rangelands,agriculture,publichealth,waterresources,andwaterdemand,yetthemechanismsbehindthechang-esarenotcompletelyunderstood.

Tobettergraspthefullrangeofspatialandtem-poralvariabil-itythatispos-sibleundernatu-ral(non-human)conditions,re-searchersattheUniversityofAr-izonaarestudy-ingthelong-termclimatehistoryofthemonsoonusingannualgrowthringsfromlong-lived,moisture-stressedtrees.

Tree Rings and the MonsoonOurunderstandingofthemonsoonclimatesystemhasimprovedgreat-lyinrecentyears,largelythroughthecooperativeeffortsofresearchassoci-atedwiththeNorthAmericanMon-soonExperiment(http://www.eol.ucar.edu/projects/name/)andim-provedseasonalforecasts.Forlon-gertimescaleclimatechangeprojec-tions,globalclimatemodelsrobust-lypredictthattheregion’scoolseasonwillbedrierinthefuture,butpredic-tionsoffutureNorthAmericanMon-soonprecipitation,inresponsetohu-man-causedclimatechange,arevaried.

Naturalproxyrecordsintheformoftreeringscanhelpputthesepro-jectionsandfuturechangesinlong-termperspective.AsdescribedintheJuly2009BorderClimateSum-mary(availableonline:http://www.climas.arizona.edu/forecasts/bor-der/archive.html),treeringsprovide

excellentrecordsforreconstructingen-vironmentalhistory,includingnatu-ralclimatevariabilityattime-scalesofyearstodecadestocenturies.

SouthwesternNorthAmericahasadensenetworkoftree-ringcollec-tionsthatextendbackmorethan400years.Historically,scientistshaveusedtheserecordstolearnaboutthelong-termhistoryofdroughtandwet-nessinthewinterseason,butthesetree-ringsamplesalsocanbeusedtostudymoisturehistoryassociatedwiththeNorthAmericanMonsoon.

Theannualgrowthringsinmanysouth-westernconiferspecies,suchaspineandfirtrees,arecomposedoflightcol-ored“earlywood”thatformsinthespringanddarkcolored“latewood”thatformsinthesummer(Figure1).IntheSouthwestU.S.andnorthwestMexico,

Figure1. This photomicrograph illustrates a sequence of four Douglas-fir tree rings (1871–1874) from southwestern New Mexico. Each annual growth ring is composed of light-colored earlywood (EW) and dark-colored latewood (LW). Both 1871 and 1872 contain intra-annual density variations known as “false rings,” which are probably related to reduced soil moisture in the May–June pre-monsoon period. Note the variability of EW-width, a function of cool-season precipitation, and the independent variability of LW width, which corresponds to warm-season precipitation.

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2 | Executive Summary

ExecutiveSummary

In General – ElNiñoisexpectedtoinfluencethewinterstormtrackandbringanincreasedchanceofabove-averageprecipitationtotheU.S.Southwestandnorth-westernMexicointheFebruary–Aprilperiod.ServicioMeteorológicoNacionalpre-dictswellabove-averageprecipitationfortheBajaCaliforniapeninsulaandnorth-westernSonorainMarchandApril.NorthwesternMexicoandthesouthwesternUnitedStatesreceivedabove-averageprecipitationduringthesecondhalfofJanuary.

Temperature –InnorthwesternMexicoandthesouthwesternU.S.,temperaturesweremostlyaveragetoaboveaverageduringJune–November2009.

Precipitation – ThankstoseveraltropicalstormsinSeptemberandOctober,BajaCaliforniaSurandSonorareceivedabove-averagefallprecipitation.Novemberwasmostlyadrymonthfortheentireregion.Precipitation Forecast–SMNpredictswellabove-averageprecipitationfortheBajaCaliforniapeninsulaandnorthwesternSonorainMarchandApril,andwellabove-averageprecipitationforBajaCaliforniaNorteandnorthwesternSonorainMay.

ENSO –ThechanceofElNiñopersistingthroughatleastAprilstandsatmorethan90percent,accordingtothelatestIRIENSOforecast.Neutralconditionsareexpect-edtoreturnrapidlyintheMay–Julyperiod,whichistypicalofElNiñoevents.

Disclaimer–Thispacketcontainsofficialandnon-officialforecasts,aswellasotherinformation.Whilewemakeeveryefforttoverifythisinforma-tion, please understand that we do not warrantthe accuracy of any of these materials. The userassumestheentireriskrelatedtotheuseofthisdata.CLIMASdisclaimsanyandallwarranties,whetherexpressedorimplied,including(withoutlimitation)anyimpliedwarrantiesofmerchantabilityorfitnessforaparticularpurpose.InnoeventwillCLIMASorTheUniversityofArizonabeliabletoyouortoanythirdpartyforanydirect,indirect,incidental,consequential,specialorexemplarydamagesorlostprofitresultingfromanyuseormisuseofthisdata.

Staff:Aaron Banas, UA Graduate Research AssistantJason Criscio, UA graduate research assistantStephanie Doster, Institute of the Environment Associate EditorLuis Farfan, CICESE Research ScientistGregg Garfin, Institute of the Environment Deputy Director for OutreachDavid Gochis, NCAR Research ScientistRebecca Macaulay, Graphic ArtistAndrea Ray, NOAA Research ScientistFundingfortheBorderClimateSummary/ResumendelClimadelaFronterawasprovided

byInterAmericanInstituteforGlobalChangeResearch(IAI)andtheNOAASectorApplicationsResearchProgram.

Climate Assessment for the Southwest


3 | Articles

ByDavidJ.Gochis,NationalCenterforAtmosphericResearch

OnMay21,2009,themonsoonmes-sagewasclear.Duringanonlinebriefing,orwebinar,forecastersandresearchersoutlinedtheirforecastsandexpectationsforthe2009NorthAmericanMon-soon(NAM)season(http://ag.arizona.edu/climate/ws/052109.htm):awetstarttothemonsoontemperedbyun-certaintybeginninginAugust.Yetastheseasonprogressed,conditionstookanunexpectedlysevereturnastherainsallbutdisappeared.So,whathappenedduringthe2009NAMseason,andhowaccuratewerethosepredictions?

Theconsensusstatementfromthewe-binarwasforanearlyandrobuston-setofmonsoonrainsintheSouthwestU.S.andnorthwestMexico,withcon-ditionsbecomingveryuncertainbymid-seasonduetothedevelopmentofanElNiñoevent(warmer-than-aver-ageoceantemperatures)inthetropi-caleasternPacificOcean.Thisconsen-susstatementwasbasedonindepen-dentforecastsmadebytheU.S.andMexicannationalweatherservices,aswellasanalysesbyclimateresearchers.

Toacertaindegree,thisgeneralfore-castturnedouttobeaccurateforalimitedregionoftheNAM,includ-ingtheborderregionsofArizona,So-nora,NewMexico,andChihuahua.Figure1showstheaccumulatedrain-fallaveragedthroughoutsouthernAri-zonaandnorthernSonorafromJuly1throughSeptember24,andevidenceexistsoftheforecastedearlyandro-bustonsetofmonsoonrainfall.

However,whatwasnotpredictedwastheseverityandextentofdrycon-ditionsthatenvelopedmuchoftheNAMregionthroughJulyintoearlySeptember.Figure1ashowsthemapofthe90-dayprecipitationanomalies

(departuresfromaverageconditions)fortheperiodendingSeptember24.Ar-easofnortheastandeasternMexico(Coahuila,NuevoLeón,Tamaulipas,andVeracruz)andportionsofsouth-ernMexico(Yucatán,Chiapas,Guer-rero,andMichoacán)weredrierthanaveragenearlyallsummerandfacedsomeoftheworstdroughtconditionsinrecenthistory.Similarly,partsofwesternArizonaandthebroaderre-gionsofthelowerColoradoRiverre-gionexperiencedrainfalltotalsap-proachingonly50percentofaverage.

Althoughitisalwaysdifficulttode-termineexactlywhatcombinationofmeteorologicaleventsleadtoob-servedseasonalpatternsofrainfall,abasicanalysisofregionalatmospher-iccirculationfeatures(weatherpat-terns)offerssomeexplanation.

Assuspectedatthetimeofthesea-sonalforecastwebinar,ElNiñoap-pearstohaveplayedasignificantroleinsuppressingmonsoonrainfall,par-ticularlyoversouthernandeasternMexico.Figure1cshowstheaver-ageseasurfacetemperatureanoma-liesforJune2bthroughSeptember16.Astrongbandofwarmer-than-aver-ageseasurfacetemperatures(around2degreesCelsiusaboveaverage)per-sistedacrossmuchofthetropicaleast-ernPacificOceanduringthesummermonthsandhascontinuedinto2010.

Abroaderregionofgenerallywarmer-than-averageseasurfacetemperaturesalsoexistedacrosstheeasternPacif-ic,GulfofMexico,andIntra-AmericaSeasregions.Pastresearchhasshownthatsuchconditionstendtoweak-entheoverallmonsooncirculation,

continued on page 5

A look back at the 2009 summer monsoon140120100

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Figure1. Summer monsoon precipitation in 2009 for northwest Mexico and the Southwest U.S. Top: green indicates cumulative precipitation greater than the 1979–1995 average, and brown indicates cumulative precipitation below the average. By the end of the monsoon season, the av-erage cumulative deficit for the region was around 40 mm. Bottom: green bars indicate the daily precipitation rate (mm/day) for the region; the black curve shows the average daily precipitation rate. Note the substantial decline in precipitation rate between July 5 and August 10, and the near cessation of precipitation between July 27 and August 10.


4 | Articles

thewidthsofthesecomponentsoftreeringscanbedistinguishedusingami-croscope,andtheyaremostoftenre-latedtoseasonalmoistureconditions;wideearlywoodbandsresultfromwetwintersandwidelatewoodbandsforminwetsummers.Conversely,earlywoodisnarrowfollowingdrywintersandlatewoodisnarrowindrysummers.

Earlywood-andlatewood-widthsvaryindependently,andthesewidthscanbemeasuredtoproducedistinctrecordsofcool-andwarm-seasonprecipitationvari-ability.ThisconceptwasdemonstratedbyDavidMekoandChristopherBaisanoftheUA’sLaboratoryofTree-RingRe-searchinasmall-scalepilotstudythatfo-cusedonsoutheasternArizona(MekoandBaisan2001).Anearlytree-ringstudyofthemonsooninMexicowaspublishedin2002byMatthewTherrell,DavidStahle,andMalcolmCleavelandfromtheUni-versityofArkansasTree-RingLaborato-ry,andJoseVillanueva-DiazoftheInsti-tutoNacionaldeInvestigacionesFores-tales,Agrícolas,yPecuarias(INIFAP)inDurango,Mexico(Therrelletal.2002).TheirresearchinMexicoisongoing.

Current ResearchIn2008,withfundingfromtheNa-tionalScienceFoundation,ateamofexpertsfromtheUA’sLaboratoryofTree-RingResearchandtheDepart-mentofAtmosphericSciencesiniti-atedanewlarge-scaleresearchproj-ecttostudytreeringsandthehistoryofthemonsooninthesouthwesternU.S.Thisthree-yearprojectwillpro-ducethefirstnetworkofmonsoon-sensitivetree-ringchronologiesforthesouthwesternU.S.(Figure2).

Theresearchershavecollectedsamplesfromtheoriginaltree-ringsitestoupdatethechronologiestothe2008calendaryearandaremeasuringtheearlywood-andlatewood-widths.Inpreviouslycol-lectedtree-ringrecords,onlytotalringwidthwasmeasuredbyearlierresearchers.

Thescientists’pri-marygoalistostudythespatialandtemporalhis-toryofthemon-soonoverthesouthwesternU.S.forthelast500yearsandaddressmanyresearchquestions:Whenweretheworstdroughtsduringthelastfivecen-turies?Howex-tremewerethesesummer-seasondroughts,andhowlongdidtheylast?Weretherepro-longedperiodsofwetter-than-av-eragemonsoons?Howdoesthemonsoonmoisturehistorycomparetothatofthewin-terseason?Whathappenedtothemonsoonduringtheseverewinter-seasondroughts(suchasthelate1500smegadrought)?Howfre-quentlyhasmajordroughtoccurredduringboththecoolandwarmseasons?Whatistherelationshipbetweenthemonsoonandlarge-scalecirculationfea-turessuchastheElNiñoSouthernOs-cillationandthePacificDecadalOscil-lation?Howwelldoregionalclimatemodelsreproducethefullrangeofvari-abilityevidentinthetree-ringdata?

Aprimarythrustoftheprojectistoworkwithregionalstakeholdersto

tree-rings, continued

provideinformationthatisusefulforresourcemanagement.Inthesummerof2011,oncethelong-termmonsoonreconstructiondatasetsarecomplete,theresearchersplantohostatechnicalworkshopforstakeholdersinthegreaterborderregion.Inthemeantime,infor-mationwillbeavailableathttp://monsoon.ltrr.arizona.edu.

For more information, contact the author at: 409 Harvill Building, University of Arizona,Tucson 85721-0076 [email protected]

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Figure2. Circles on this map illustrate the monsoon-sensitive tree-ring chronology network currently being developed for the southwestern United States by researchers from the University of Arizona’s Laboratory of Tree-Ring Research. Triangles illustrate the complementary Mexican chronology network developed by our colleagues from the Instituto Nacional de Investigaciones Forestales, Agrícolas, y Pecuarias (INIFAP) in Mexico and the University of Arkansas Tree-Ring Laboratory.

ReferencesMeko,D.M.,andC.H.Baisan.2001.Pilotstudyoflatewood-widthofconfersas

anindicatorofvariabilityofsummerrainfallinthenorthAmericanMonsoonregion:International Journal of Climatology,21:697–708.

Therrell,M.D.,D.W.Stahle,M.K.Cleaveland,andJ.Villanueva-Diaz,2002.WarmseasontreegrowthandprecipitationoverMexico.JournalofGeophysicalRe-search,107,no.D14,4205,10.1029/2001JD000851.


5 | Articles

summer monsoon, continued

becauseoneofthekeyfactorsinflu-encingmonsoonstrengthisthecon-trastbetweenoceanandlandtem-peratures,withrelativelycooloceanandwarmlandtemperatureslead-ingtoincreasedmonsoonactivity.

Anotherfactorthatinhibitedmonsoonrainfallduringsummer2009wasaneastwarddisplacementofhighpressurenearthetopoftheatmospherebetweenJune24andSeptember16.Upperat-mospherehighpressureusuallyhelps

Figure2a.Accumulated precipitation anomalies (observed precipitation minus the 1979–1995 average) for June 26–September 24, 2009. Note the widespread region of below-average pre-cipitation across most of Mexico and the Southwest U.S.

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Figure2b.Sea surface temperature (SST) anomalies (observed minus 1979–1995 average) for the 2009 monsoon season. The large region of above-average SSTs along the equator in the eastern Pacific Ocean is characteristic of an El Niño event. El Niño usually inhibits summer monsoon precipitation in northern Mexico and the Southwest U.S., but it enhances winter precipitation in the region.

steermoistureintoSouthwestU.S.andnorthwesternMexico,buttheeastwarddisplacementofhighpressureresultedindrier-than-averageflowfromthewestandnorthintothemonsoonregion.

Relatedtothisupperatmospherecir-culationpatternisthefactthatfewer-than-averagetropicalstormshitlandinboththeeasternandwesternpor-tionsoftheNAMregion.In2008,fournamedPacificsystemsmadedirectland-fallorcamewithin50milesofBajaandthewestcoastofmainlandMex-ico,whereasonlytwonamedsystems(HurricaneAndresonJune21–24andHurricaneJimenaonAugust29–Sep-tember4)madelandfallfromthePa-cificduringthe2009monsoonseason.

Forecastsfromcomputermodels(“dy-namicalmodelforecasts”)wereonecomponentoftheconsensusforecastdescribedabove.Whilethedynamicalmodelspredictedalater-than-observedonsetofthemonsoon,theydidarea-sonablejobofpredictingthespatialpat-ternsofwet(northwestMexico)anddryconditions(southernandeasternMex-ico)duringJuly.However,bymidAu-gusttheyhadlargelyunderestimatedtheincreasingdegreeofdrynessthrough-outmuchofthemonsoonregion.Thisshortcominginpredictingthemagni-tudeofwetanddryperiodsissomewhatsimilartothe2008monsoonforecasts(seetheOctober2008BorderClimateSummaryathttp://www.climas.arizo-na.edu/forecasts/border/archive.html).

Insummary,the2009monsoonsea-sonwascharacterizedbydrier-than-averageconditionsacrossmuchoftheregion.Whileseasonalfore-castsshowedsomeskillduring2009,muchroomforimprovementre-mainsinpredictingtheseverityofwet-ter-ordrier-than-averageconditions.


6 | Recent Conditions

TemperatureLookingbackatJune–November2009,temperatureswerewellaboveaverageacrosstheentireMexico-U.S.borderre-gionduringthesummermonths(notshown);areasinsouth-easternArizonaacrosstowestTexaswere2degreesCelsiuswarmerthanthelong-termaverage.ForSeptember–Novem-ber(Figure1b),above-averagetemperaturesoccurredmost-lyfromCaliforniatosouthwesternNewMexico,whilesomeareasofsouth-centralNewMexicotowestTexassawaveragetobelow-averagetemperatures.Above-averagetemperaturesinthesouthwesternU.S.wereassociatedwithbelow-averagesummermonsoonprecipitationandlong,relativelydryspellsfrommid-JulyuntillateAugust.Someofthiscanbeas-cribedtotheElNiñoepisodethatbeganduringthesummer;ElNiñohasatendencytosuppressthenorthwardextentofmonsoonmoisture.InnorthwesternMexico,temperatures

Notes:Maps of recent temperature conditions were produced by the National Oceanic and Atmospheric Administration’s Climate Prediction Center (NOAA-CPC). Temperature anomalies refer to departures from the 1971–2000 arithmetic average of data for that period.

Figure 1a. Mean temperature at 2-m elevation for November 2009.

Figure 1b. Mean temperature at 2-m elevation for September–November 2009.

5 10 15 20 25 30 35Degrees Celsius

Figure 1d. Mean temperature departure from 1971-2000 average at 2-m elevation for September–November 2009.

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Figure 1c. Mean temperature departure from 1971-2000 average at 2-m elevation for November 2009.

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OntheWeb:For more information: http://www.cpc.ncep.noaa.gov/products/Drought/Atm_Circ/2m_Temp.shtml

weremostlyaveragetoaboveaverageduringJune–November2009.TemperaturesweremostlyaboveaverageduringSep-tember-November(Figure1d),withsomecoolerthanaver-agetemperaturesinDurangoduringNovember(Figure1c).

OntheWeb:For more information: http://www.cpc.ncep.noaa.gov/cgi-bin/US_anom_realtime.sh

Precipitation



Precipitationwasmostlybelowaverageduringthesum-merandearlyfallmonthsnorthoftheborderbutrangedfrombelowaverage(BajaCaliforniaSur)toaboveaverage(Chihuahua)southoftheborder.Neartheborder,areasofabove-averagesummerprecipitationincludedsoutheasternNewMexico,northernChihuahua,andwestTexas.Furthersouth,JunewaswetterthanaverageinChihuahua,Duran-go,SinaloaandSonora,andstatewidesummerprecipitationwasnearaverageformostofnorthernMexico,withthefol-lowingexceptions:Chihuahuarecordedabove-averagepre-cipitationandSinaloarecordedbelowaverage.Thankstosev-eraltropicalstormsinSeptemberandOctober,BajaCalifor-niaSurandSonorareceivedabove-averagefallprecipitation.Inrain-relatednews,around200,000peopleinGuaymas

Figure 2b. United States and Mexico precipitation percent of 1971-2000 average for September–November 2009.

Figure 2a. United States and Mexico precipitation percent of 1971-2000 average for June–August 2009.

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Figure 2c. United States and Mexico precipitation for September–November 2009.

Figure 2d. United States and Mexico precipitation for November 2009.

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andEmpalmewerecutofffrombasicservicesandatleast30neighborhoodsofbothcitieswerefloodedwhenmorethan632.5millimetersofrainfellduringHurricaneJimenabe-tweenAugust29–September4.FlorencioDíazArmenta,adelegatefromtheComisiónNacionaldelAgua(Conagua),notedthatprecipitationneartheportsurpassedtherecordsetin1948of340millimeters(El Imperial,September4).

Notes:Maps of recent precipitation conditions were produced using data from the National Oceanic and Atmospheric Administration’s Climate Prediction Center (CPC). Precipitation anomalies refer to departures from the 1971–2000 arithmetic average of data for that period. Percentage of normal is masked out where normal precipitation is less than 0.1 mm per day.

OntheWeb:For more information: http://www.cpc.ncep.noaa.gov/products/Drought/Atm_Circ/2m_Temp.shtml


NorthAmericanDroughtMonitor



OntheWeb:For more information: http://www.ncdc.noaa.gov/oa/climate/monitoring/drought/nadm/

TheNorthAmericanDroughtMonitormap(Figure3)showsdroughtacrossthesouthwesternU.S.andnorth-westernMexico.Followingamoderatelywet2008–09win-terbutexceedinglydry2009summerandfall,ArizonaandsouthernCaliforniaexhibitedseveredroughtcondi-tions.ThemajorimpactsinArizonaincludeddrawdownoftheSanCarlosReservoirontheUpperGilaRivertoal-mosthistoricallylowlevelsanddegradationofrangelandconditions.BetweenAugustandNovember,reservoirlev-elsincreasedinmostreservoirsinSonora(notshown;basedondatafromComisiónNacionaldelAgua),withtheexceptionofthemostsouthernSonoranreservoirs.

Indrought-relatednews,watersavingsfromthemois-tureaccumulationfrompreviousrainfallreachednear-ly80millioncubicmeters,accordingtotheIrrigationDistrictoftheRioYaqui(IDRY).Thedirectorofopera-tions,HumbertoBorbón,estimatedthatthevolumenotusedbythereservoirsystemwouldirrigatebetween7,000and8,000hectares(about17,300to19,700acres)dur-inganentirecropcycle(El Imperial,November2).

OntheU.S.sideoftheborder,UniversityofCaliforniare-searchersestimatedthat2009watershortagesledtoloss-esof21,000jobsand$703millionincentralCalifornia’sSanJoaquinValley(CaliforniaDroughtUpdate,September30).InotherCaliforniadroughtnews,theCaliforniaBuild-ingStandardsCommissionapprovedtheCaliforniaDualPlumbingCode,whichdelineatesstatewidestandardstoin-stallbothpotableandrecycledwaterplumbingsystemsincertaintypesofbuildings.Thecodeappliestocommercial,retail,andofficebuildings,andseveralotherpublicbuild-ings.Recycledwaterwillbeusedforbuildingcoolingandtoiletflushing(CaliforniaDroughtUpdate,November30).

Notes:The North American Drought Monitor maps are based on expert assess-ment of variables including (but not limited to) the Standardized Precipi-tation Index, soil moisture, streamflow, precipitation, and measures of vegetation stress, as well as reports of drought impacts. It is a joint effort of several agencies, including NOAA’s National Climatic Data Center, NOAA’s Climate Prediction Center, the U.S. Department of Agriculture, the U.S. National Drought Mitigation Center, Agriculture and Agrifood Canada, the Meteorological Service of Canada, and the National Meteo-rological Service of México (SMN - Servicio Meteorológico Nacional).

Figure 3. North American Drought Monitor (releasedNovember 30).

Drought Impact Types

Delineates Dominant Impacts

A = Agricultural (crops, pastures, grasslands)

H = Hydrological (water)

AH = Agricultural and Hydrological

D3 Extreme Drought

D4 Exceptional

Drought Intensity

D0 Abnormally Dry

D1 Moderate Drought

D2 Severe Drought

SonoranReservoirLevels


OntheWeb:For more information: http://www.elimparcial.com



MostofSonora’sreservoirsarewellbelowmaximumstoragecapacitybutseveral,includingLázaroCárde-nas,P.ElíasCalles,ÁlvaroObregón,AbrahamGonzález,andA.RuizCortines,areatnear-orabove-averagestor-agecapacity(Figure4).NovemberstoragelevelsinLázaroCárdenasandAbrahamGonzálezwereabove2008levels,butotherreservoirswerebelow2008lev-els.TotalNovember2009reservoirstorageforSono-rawas170cubichectometersbelow2008levels.

Notes:The map gives a representation of current storage levels for reservoirs in Sonora. Reservoir locations are numbered within the blue circles on the map, corresponding to the reservoirs listed in the table. The cup next to each reservoir shows the current storage level (blue fill) as a per-cent of total capacity. Note that while the size of each cup varies with the size of the reservoir, these are representational and not to scale. The table details more exactly the current capacity level (listed as a percent of maximum storage, and percent of average storage). Current and maximum storage levels are given in cubic hectometers for each reservoir. One cubic hectometer is one billion liters.

This map is based on reservoir reports updated daily in El Imparcial (http://www.elimparcial.com), using data provided by Comisión Nacio-nal del Agua.

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Figure 4. Sonoran reservoir levels for November 2009 as a percent of capacity. The table lists current, average, and maximum storage levels.

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4. I.R. Alatorre

5. Álvaro Obregón

6. A. Ruiz Cortines

7. P. Elías Calles

8. Lazaro Cárdenas

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CLIMASwww.climas.arizona.edu


10 | Forecasts

OntheWeb:For more information: http://www.hydro.washington.edu/forecast/westwide/sflow/index.6mons.shtml#seas_vol

StreamflowForecast

Notes:The forecast information provided in Figure 5 is updated monthly by the University of Washington and Princeton University using ensemble streamflow prediction (ESP) techniques. The average of a group (ensemble) of forecasts is generated by using recent meteo-rology to initialize the Variable Infiltration Capacity (VIC) hydrologic model. Streamflow volume estimates are based on 40 VIC model runs, using meteorological data from the period 1960–1999. These esti-mates, shown in Figure 5, are expressed in terms of the percent of the 1960–1999 average streamflow at each gage.

Thesix-monthEnsembleStreamflowPrediction(ESP)fore-cast,releasedJanuary18bytheUniversityofWashing-tonandPrincetonUniversity,predictsmostlybelow-av-eragestreamflowfortheperiodJanuary–June(rangingfrom30percentbelowaverageto10percentaboveaver-age)forgagesonbothsidesoftheMexico-U.S.borderre-gion.Theaverageflowisbasedontheperiodfrom1960through1999.Mostofthestreamflowforecastsforthere-gioninFigure5predictsix-monthstreamflowvolumesof70to90percentofaverage.Evenlowerflowsarepredict-edforthegagesatImuris(#15)innorthernSonoraandLasSardinasinnorthernDurango(#36).LowstreamflowsalsoareforecastfortributariesoftheColoradoRiverintheU.S.Itisverylikelythatmostofthesepredictionswillchangewhentheforecastsareupdated,becausethesefore-castswereinitiatedbeforeaseriesoflateJanuaryandear-lyFebruarystormsbroughtlargeamountsofprecipitationtotheLowerColoradoRiverBasinandnorthernMexico.

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11. San Joaquin2. Boquilla3. Hoover Dam4. Davis Dam5. Parker Dam6. Alamo Dam7. Imperial Dam8. Virgin, UT 9. Near Hurricane, UT10. Little�eld, AZ11. Lee’s Ferry12. Desert View, AZ13. Near Cameron, AZ14. Near Grand Canyon15. Imuris16. Near Blu�, UT17. Oviachic18. La Junta19. Novillo20. Cubil

21. Paso Nacori22. Angostura23. Guadalupe24. Huapaca25. Casas Grandes26. Near Mcphee, CO27. Near Bay�eld, CO28. Navajo Reservoir29. Abraham Gonzalez30. Albuquerque31. Ixpalino32. Near Del Norte, CO33. Near Lobatos, CO34. Near Chamita35. Villalba36. Las Sardinas37. Zacatecas

>170150–170130–150110–13090–11070–9050–7030–50<30

% of normal

Figure 5. United States and Mexico stream¡ow forecast for January–June.

OntheWeb:For more information: http://smn.cna.gob.mx/productos/map-lluv/p-clim02.gif

PrecipitationForecast


11 | Forecasts

Notes:This forecast was prepared by the Servicio Meteorológico Nacional (SMN). The forecast methodology was developed by Dr. Arthur Douglas (Creighton University, retired) in collaboration with SMN scientists.

The forecasts are based on the average of precipitation values from analogous years in the historical record. Selection of analogous years is based on statistical analysis of factors in oceanic and atmospheric circulation known to influence precipitation in Mexico. Unique com-binations of climate indices are used in the forecasts each month. A statistical method known as cluster analysis is used to identify evolving climate patterns observed in the historic record and place each year in historical context; the years with the evolving climate patterns most similar to the current year are selected. Average atmospheric flow patterns and surface precipitation anomalies are constructed with the historic data and compared with the climatological average.

Examples of atmospheric and oceanic factors used in identifying ana-logue years, include: Pacific and Atlantic Ocean temperatures, tropical upper atmosphere oscillations, the position and strength of persistent high and low atmospheric pressure centers, and other factors.

The maps show predicted percent of monthly average precipitation. The legend shows the ranges of predicted percent of average precipita-tion associated with each color. Blues and greens indicate above-aver-age precipitation; yellows and reds indicate below-average precipita-tion. White indicates precipitation within 20% of the climatological average (based on data from 1941-2002).

TheServicioMeteorológicoNacional(SMN)forecasts,is-suedinearlyFebruary,arebasedonyearswithsimilarpat-ternsofprecipitation,atmosphericcirculation,andoceantemperatures,whichaffecttheclimateoftheregion;forthisforecast,theyearsare1969,1980,1988,and1992.SMNpredictswellabove-averageprecipitationfortheBajaCali-forniapeninsulaandnorthwesternSonorainMarchandApril,andwellabove-averageprecipitationforBajaCalifor-niaNorteandnorthwesternSonorainMay(Figures6a–c).ForecastsforAprilandMayshowincreasingchancesofbe-low-averageprecipitationinBajaCaliforniaSur.SMNfore-castsaveragetoabove-averageprecipitationformostofChi-huahuaandDurango,andmorethan50percentgreater-than-averageprecipitationforthesestatesinMay,amonthwitharelativelylowpercentoftheannualtotalprecipita-tionforthesestates.Forecastsofbelow-averageprecipitationforstatesalongcontinentalMexico’swestcoastareconsis-tentwithclimatepatternsforElNiñoevents.TheseforecastsfromtheNOAA-ClimatePredictionCenter(notshown)agreewellwithforecastsfortheU.S.-Mexicoborderstates.

Figure 6a. Precipitation forecast for March 2010 (released February 1, 2010).

Figure 6b. Precipitation forecast for April 2010 (released February 1, 2010).

Figure 6c. Precipitation forecast for May 2010 (released February 1, 2010).

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Notes:Figure 7a shows the standardized three-month running average values of the Southern Oscillation Index (SOI) from January 1980 through May 2009. The SOI measures the atmospheric response to sea surface temperature (SST) changes across the tropical Pacific Ocean. The SOI is strongly associ-ated with climate effects in parts of Mexico and the United States. Values greater than 0.5 represent La Niña conditions, which are frequently associ-ated with dry winters and sometimes with wet summers in the southwest-ern U.S. and northwestern Mexico. Values less than -0.5 represent El Niño conditions, which are often associated with wet winters in those regions.

Figure 7b shows the IRI probabilistic El Niño-Southern Oscillation (ENSO) forecast for overlapping three month seasons. The forecast expresses the probabilities (chances) of the occurrence of three ocean conditions in the ENSO-sensitive Niño 3.4 region, as follows: El Niño is defined as the warm-est 25 percent of Niño 3.4 SSTs during the three month period in question, La Niña is defined as the coolest 25 percent of Niño 3.4 SSTs, and neutral conditions are defined as SSTs falling within the remaining 50 percent of observations. The IRI probabilistic ENSO forecast is a subjective assess-ment of monthly model forecasts of Niño 3.4 SSTs. The forecast takes into account the indications of the individual forecast models (including expert knowledge of model skill), an average of the models, and other factors.

Year

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alue

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Figure 7a. The standardized values of the Southern Oscillation Index from January 1980–December 2009. La Niña/El Niño occurs when values are greater than 0.5 (blue) or less than -0.5 (red) respectively. Values between these thresholds are relatively neutral (green).

2.52.01.51.00.5

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CLIMASwww.climas.arizona.edu

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Figure 7b. IRI probabilistic ENSO forecast for El Niño 3.4 monitoring region (released January 21). Colored lines represent average historical probability of El Niño, La Niña, and neutral.

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OntheWeb:For more information: http://iri.columbia.edu/climate/ENSO/currentinfo/update.html


12 | Forecasts

ModerateElNiñoconditionsintheequatorialPacificOceancontinuedthroughDecemberandJanuary,withseasurfacetemperatures(SSTs)remaining1.5degreesCelsiusaboveav-erageacrossmuchofthecentralandeasternpartsoftheba-sin.TheInternationalResearchInstituteforClimateandSo-ciety(IRI)notesthatthepatternofabove-averageSSTshasbecomemoreorganized;thusthisinitiallyweakElNiñoeventhasevolvedintoapatternmoretypicalofpastElNiñoevents.TheSouthernOscillationIndex(SOI;Figure7a)remainednegativeinDecember,indicatingthattheat-mospherewasrespondingtotheabove-averageSSTs.Inre-centweeks,subsurfacewatertemperaturesalongtheequa-toralsohaveremainedwellaboveaverage,indicatingthatthiswarmwaterwillhelpincreaseSSTsincomingweeks.

AllofthesesignspointtowardsthecontinuationofatleastweaktomoderateElNiñoconditionsforthenextsever-almonths.ThechanceofElNiñopersistingthroughatleastAprilstandsatmorethan90percent,accordingtotheJanuary21IRIENSOforecast(Figure7b).Neutralcon-ditionsareexpectedtoreturnrapidlyintheMay–Julype-riod,whichistypicalofElNiñoevents,becausetheynor-mallydissipateinthespring.Inthemeantime,ElNiñoisexpectedtoimpactwinterweatherintheU.S.-Mexicoborderregionoverthenextseveralmonths.Astrongsub-tropicaljetstream,forminginresponsetotheunusual-lywarmwatersintheeasternPacific,isexpectedtoinflu-encethewinterstormtrackandbringanincreasedchanceofabove-averageprecipitationtotheU.S.SouthwestandnorthwesternMexicointheFebruary–Aprilperiod.

ENSO(El Niño – Southern Oscillation)

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