TheAndesChap.1-GeographicalcontextChap.2-Largescaleclimate

RenéD.Garreaud

GeophysicsDepartment–UniversidaddeChileCenterforClimateandResilienceResearch,CR2

WealllovetheAndes…..

•Morethan6000kmlong,fromtheCaribbeanseatoPatagonia•Verytallmountain,speciallyattropical/subtropical(>5000mASL)

•Watertowerfor50Millionspeopleinsevencountries•Anearly2DmountainwhenconsideringsynopUc-scaleflow•ExposedtoeasterliesanddeepconvecUonatlowlaUtudes•ExposedtowesterliesandfrontalsystemsinmidlaUtudes•Plentyofpaleo-records(glaciers,trees,lakesediments….)

•Manymysteriestobesolved

Nonetheless

•Itsextremegeographysetthestageforhydromet.hazards•Undersampled(meteorology+hidrology)

•HighlysensiUvetoclimatechange

Bogota

Medellin

Cali

Quito

Cuenca

Huaraz

Lima

Oruro

Santa Cruz

Tarija

La Serena

Salta

Tucuman

Mendoza

Calama

San;ago

Villarica

Coyhaique

Merida

Natales

Caracas

7.2

12.1

10.2

3.0

1.0

Cuzco

Arequipa

Juliaca La Paz

1.5

5.0

1.5

.8

Σ∼50Mill

>5000 < 5

m ASL

>1000 < 1

p/km2

Topography PopulaUon(2015)

Bariloche

Esquel

Eq

10°S

20°S

30°S

40°S

50°S

>3000 < 50

mm/yr

PrecipitaUon

BasicFeatures

BasicFeatures

Sealevel

Wetslip

Plentyofsedimenttransport

Abundantrainfall

Dryslip

Lidlesedimenttransport

Deficientrainfall

Sealevel

NazcaPlate

NazcaPlate

AdaptedfromLambandDavis;Nature2003

Climate–Tectonics-Geomorphology

Garreaudetal.2009

E

W

a. DJF

E

W

b. JJA

Zonal (east-west) mean flow over the AndesBrown area: Terrain mean height

Dashed line: 500 hPa, half of the atmosphere below!

Latitude Latitude

Km 12

5.

0.

ChocoLLJ

CoastalLLJ

CAO

SALLJET

Thecomplexmid-andlow-levelflowneartheAndes

Jiangetal.2013

Illustrationofthecomponentsofsurfacewaterbalanceandatmosphericwaterbalanceforthe observations and reanalysis datasets in the Andes and Amazonia sub regions of theAmazonRiverbasin.Valuesareinunitsofmm.y-1.Thearrowconventiononthebottomleftrepresents1000mm.y-1.Datasource:Builes-JaramilloandPoveda,2018.

Another“ocean”totheeast….Andes-AmazonconnecUons

South America monsoonal regime and Altiplano rainfall

Mean annual cycle Colors: OLR (proxy of precipitation) Streamlines: 200 hPa (~12 km) wind

Bolivian High

Nowyouseeit…nowyoudon’tWhatcontrolstheBHatsubmonthlyUmescales

Summer Altiplano rainfall: Intraseasonal variability

Falvey and Garreaud 2005

ConvecUverainfallalsoexhibitsapronounceddiurnalcycle

Seasonalmarchofthediurnalcycleofrainfallat17selectedstaUonsinthetropicalAndesofColombia.Thediurnalcycleisdefinedfrom0700to0700LST,andinterpolatedisolinesindicatepercentoftotaldailyrainfall,withthecolorscaleshownatthebodom.Boundariesoftheneighboring(lel)Caucaand(right)MagdalenaRivervalleysareshowninwhite.TheinsetatthebodomlelshowsdetailsofraingaugeslocatedinthewesternflankoftheCentralrangeoftheAndes.Source:Povedaetal.(2005).

PrecipitacionenLa-tudesmediasModestannualcycleintheextratropics

4

1

2

3

DistribuUonofmeanannualrainfallovertransect(around6°N)alongthethreerangesoftheColombianAndes(Poveda)

Espinonzaetal.2015

DistribuUonofmeanannualrainfallovertransect(around33°S)alongthesubtropicalAndes

?

Wheredoesitrainmore?TheelusiveOrographicPrecipitaUon

Gradient(OPG(laUtude))

CentralChileclimate

P∼300mm/yrShortrainyseason(JJA)T∼15ºC(annualmean)

CentralChileAgriculture…amiracle?

P∼300mm/yrShortrainyseason(JJA)T∼15ºC(annualmean)

TheAndeanCredit

UpperbasinA∼5.000km2P∼900mm/yr

Lowerbasin,nonarableA∼7.000km2P∼300mm/yr

Lowerbasin,arableA∼3.000km2P∼300mm/yr+700mm/yr+300mm/yr=1.300mm/yr

HowdoesthespaUalvariabilityinsurfaceparametersandmeteorologyaffectwateravailability(e.g.riverflow)?

2001 2002

Jan Jul Jan Jul Jan0

50

200

600

Dailym

eanriv

erflow

(m3 /s) LowerMapocho

2a2b

3

Snowmeltregime,withstrongyear-to-yearvariability(1aversus1b)Winterstorms(2),non-linear(2a/2b),withsuddenpeakflow(3)

UpperMaipo

0

200

San-agorainfall[mm]

1a 1b

DrWouterBuytaert:

OtherformsofAndeanCredit

SillitoeandPerello,2005

OtherformsofAndeanCredit

FloodingofMocoa,Putumayo,Colombia,onApril1st,2017

Atleast300fataliUes.

LandslideSanUagofoothills,May3,1993Atleast100fataliUes.

ButlivingclosetotheAndeshasitsrisk

Strongerupper-LevelSTJet

Climo.StormTrack

ENyearsStormTrack

H

BlockingHigh

WeakenedSTHigh

H

Drier/WarmerDJF

Weder-OND

Weder-JJA

Drier-DJF

Colder

Interannualvariability:MajorENSOimpactsalongtheAndes

Weder-JFMA

Warmer-DJF

AllstaUons(anyUme,anylength)Century-longstaUons(Ti<1905,Tf>1995,missdata<20%)

PrecipitaUon MeanTemperature

GlobalHistoricalClimateNetwork(GHCN)

Hydro/metobservingsysteminthehighAndes

Currentcoverage(DGA+DMC,pinkcircles)isreasonableinthe“centralvalley”butdramaUcallylowathigherelevaUons,wheremostofthewateraccumulaUontakesplace

HowmuchreallyrainsinthecentralAndes?Differentproducts,differentplaces…

RegularsoundingstaUons

Lima LaPaz

SubtropicalWesterlies

ExtratropicalWesterlies

TropicalEasterlies

MountaininducedcirculaUon:subsidencewestoftheAndes

Bogota

Quito

Salta

San;ago Natales Lima

La Paz

Tropical Glaciers

Central Andes Glaciers

Seasonal snow Pack / Glaciers

NPI + SPI

0°C DJF

0°C JJA

Arequipa

BasicFeatures

Andes crest height

Precipita;on atop of the Andes (mm/yr)

9.000

3.000

300