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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