the andes chap. 1 - geographical context chap. 2 - large ... · current coverage (dga+dmc, pink...
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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