Climas

Extraños

usando

PLASIMRené Garreaud & Alejandra

Molina

DGF-UCH

Climas

Extraños

usando

PLASIMRené Garreaud & Alejandra

Molina

DGF-UCH

Model Validation

Rotation Experiments

Topography Experiments

Model Description

RG: Conoces

algun

modelo

climatico

“simple” de usar?SS: Claro

che…hay algo

llamado

Puma Model…

Pero

buscar

“Puma Model” en Interner

puede

ser peligroso…

Full (atmos+ocean+ice)

Atmos-only (prescribed ocean/ice)

SON mean SST

Model Validation

Weak cold tongue, small warm pool, too much ice

Zonal mean, annual mean

Prec

ipita

tion

[mm

/day

]SL

P [h

Pa]

CMAPFull (Atmos+Ocean+Ice)Atmos

only

Latitude

Model Validation

Full

Atmosonly

Obs.

DJF Precip JJA Precip

Model Validation

360

180

150

120

90

60

Model Validation

DJF mean SLP

Full

Atmosonly

ObsNNR

Model Validation

Full

Atmosonly

ObsNNR

DJF mean 200 hPa winds

Feature Atmos-Only Full

Cold tongue Of course weak

Warm pool Of course Small

ITCZ Ok, too wide Too strong, too zonal

South American Monsoon Yes Yes

SH Storm Track Yes Yes

Orographic precipitation Yes Yes

Subtropical deserts Yes, but too small Yes, but too small

Subtropical anticylones Yes, but too wide Ok, too wide

SPCZ Yes No

SACZ Ok, but too short Yes

Model Validation

Atmos-Ocean model includes more processes but it has a less realistic representation of the basic state

TopographyRotation Precipitation

SST

Circulation

Atmos.only model

Atmos-Oceanmodel

Fariasmodel

Model Validation

Full (a-o-i) ControlFull, Inverse rotationFull, slow rotation (10 days)

Rotation Experiments

Annu

al m

ean

prec

ipita

tion

[mm

/mon

th]

Control (lines) and slow-rot (shaded) annual mean precip

[mm/month]

150

150

360

180

150

120

90

60

Rot

atio

n E

xper

imen

ts

Control

Inv. Rot

Slow Rot

DJF surface winds

Rotation Experiments

Inverse-Rot minus Control SST/SAT

SON

MAM

°C

Rotation Experiments

DJF mean Precip JJA mean Precip

InvRot

InvRotMinusControl

Control360

180

150

120

90

60

mm/month

Rotation Experiments

DJF mean Precipitation

(a) Control (b) Inverse Rotation (c) InvRot

minus Control

Topography Experiments

Topography Experiments

Topography Experiments

Motivated by the previous wisdoms in the paleo-climateand geological communities, we set up a numerical experiment using PLASIM:

Experiment Topography Ocean/Ice model

Control 100% Yes

Atmos

Only 100% No

0.1Topo-f 10% everywhere Yes

0.3Topo-f 30% everywhere Yes

0.5Topo-f 50% everywhere Yes

0.7Topo-f 70% everywhere Yes

0.9Topo-f 90% everywhere Yes

0.3Topo-A 30% everywhere No

0.3Andes-f 30% South America Yes

0.3Andes-A 30% South America No

Topography Experiments

0.3*Topo

minus Control (DJF)

900 hPa winds and Precip % Precip

(P/Pc)

+

mm/day %

R>100 mm/month R< 10 mm/month

Control

0.3*AndesControl

0.3*Andes

Topography Experiments

DJF Precipitation

f = 0.1

f = 0.9

f = 0.7

f = 0.3

f = 0.5

f* = 0.3

Topo

grap

hy E

xper

imen

ts

mm/day

f*Topo

minus Control (DJF)

Topographic reduction factor

Prec

ipita

tion

chan

ge [P

e/Pc

*100

%]

Andes only

Interannualvariability ()

SESA(15-25°S 60-50°W)

Austral Andes(45-50°S 80-70°W)

Topography Experiments

Topo

grap

hy E

xper

imen

ts

-27°C

-37°C

-47°C

R>100 mm/month

UpwardSubsidence

Cold Adection

Deep convections warms the tropical / subtropical tropospher, producing a warm-core upper-level anticyclone

Strong cold advection occurs where the westerly flow “encounters” the upper-level warm region. Thermal balance requires enhanced susbidence, strengthening the SEP subtropical anticyclone

P (less precip)

T (cooling)

0.3Andes -

Control

Control

Control

Rodwell-Hoskins Mechanism

Smaller Andes reduce rainfall over the interior of the continent and thus reduce the warming of the upper-troposphere…less thermal gradient…less cold advection….less subsidence?

Topography Experiments

Temperature advection [10*K/day]

Ver

tical

vel

ocity

[cm

/s]

SEP anticyclone

SACZ

Central SA

Subsidence

Upsidence

DJF 400 hPa South American Region (60°S-20°N, 220°-360°E)

Topography Experiments

Temperature advection [10*K/day]

Vertical velocity [cm/s]

Control

0.3Andes

Control

0.3Andes

Control0.3Andes

w

0.3 cm/s

DJF, 400 hPa

Rotation Experiments

Inverse-Rot minus Control SST/SAT

SON

MAM

°C

Rotation Experiments

Topography Experiments

0.3*Topo

minus Control (DJF)

900 hPa winds and Precip % Precip

(P/Pc)

+

mm/day %

R>100 mm/month R< 10 mm/month

Control

0.3*AndesControl

0.3*Andes

Topography Experiments

DJF Precipitation