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Coupled Variability in CCSM3. Michael Alexander Climate Diagnostics Branch Physical Science Division (PSD) Earth System Research Laboratory (ESRL) Was The Climate Diagnostics Center Christophe Cassou, Clara Deser , Young-Oh Kwon, Adam Phillips. Selective Survey. ENSO

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coupled variability in ccsm3
Coupled Variability in CCSM3

Michael Alexander

Climate Diagnostics Branch

Physical Science Division (PSD)

Earth System Research Laboratory (ESRL)

Was

The Climate Diagnostics Center

Christophe Cassou, Clara Deser, Young-Oh Kwon,

Adam Phillips

selective survey
Selective Survey
  • ENSO
    • SST, precipitation
    • Global Teleconnections
  • Winter Time Climate/Variability
    • Patterns: PDO, PNA, NAO/AO, PNA
  • Extratropical Upper Ocean Processes
    • Seasonal cycle of Temp, MLD
    • Winter-to-winter recurrence of SST Anomalies
  • For more information see:

http://www.ccsm.ucar.edu/publications/jclim04/Papers_JCL04.html

tropical sea surface temperature
Tropical Sea Surface Temperature

CSM2

Nino3.4

CSM3

T42

CSM3

T85

OBS

power spectrum of sst nino3 4 index
Power Spectrum of SST Nino3.4 Index

T42 CSM3

T42 CSM2

OBS

T85 CSM3

enso sst composite
ENSO SST Composite

Observations

CSM3 T85

warm cold enso composites djf
Warm - Cold ENSO Composites (DJF)

SST

Precipitation

T42 similar

99% sig.

pdo 1st eof of winter sst anomalies
PDO: 1st EOF Of Winter SST Anomalies

CCSM3 T42 (Yr : 100 – 999; 26 %)

CCSM2 (T42) (Yr : 350 – 999; 20 %)

CCSM3 T85 (Yr : 100 – 599; 28 %)

Observation (ERSST : 1901 – 2000; 28 %)

power spectrum winter sst kuroshio extension index
Power Spectrum Winter SST Kuroshio Extension Index

Observation (ERSST: 1901-2000)

~20 yr

CCSM3 T85 (100-599)

~16-20 yr

regression on sst kuroshio extension index
Regression on SST Kuroshio Extension Index

+2ºC per ºC SST KEI

+50 W/m2 per ºC SST KEI

SST (Winter)

Warm SST ~

Heat Flux from Ocean to Atmosphere

QNET (Winter)

(Contour Interval: 0.2ºC/ºC, 10 W/m2/°C ; Shading: significant at 99 %)

  • Local QNET responds to the SST anomaly, rather than forcing it.
lead lag correlations in the kuroshio extension region
Lead/-lag correlations in the Kuroshio Extension Region

Warmer SST

Heat

Convergence

Heat

Convergence

Geostrophic Heat Divergence vs. QNET

Heat Flux out of Ocean

Geostrophic Heat Divergence vs. SST

(Low-pass Filter > 10 yr)

Ocean heat convergence  +1-2 yr  warmer SST  +1~2 yr  ocean-to-atmosphere QNET

pacific patterns in ccsm3 correlations with t air
Pacific Patterns in CCSM3& correlations with Tair

Patterns from

Cluster analyses

Atm Response:

El Nino ≠-La Nina

e.g. ALE+ most

Prevalent in Nina

annual cycle of temperature c mld central n pacific region 25 n 45 n 165 e 175 w
Annual Cycle of Temperature (ºC) & MLDCentral N. Pacific Region: 25ºN-45ºN,165ºE-175ºW

CCSM

Levitus

Reemergence

Mechanism

slide20

Reemergence in the Central North PacificLead-lag Correlations between the Temp´(month,depth) with Temp´ at the Base Point (Aug-Sep,~50-82m)

0.3

0.6

0.6

Depth (m)

summary of ccsm3 variability
Summary of CCSM3 Variability

ENSO

  • Reasonable timing and amplitude but too biennial compared to nature and too meridionally confined
  • SLP response over the North Pacific in boreal winter is excellent in T85 version, too weak in T42 version

PDO

  • Leading EOF of CCSM3 winter SST have PDO-like horse-shoe pattern. Amplitude too large in the west
  • Robust decadal (16-20 yr) SST variability in the Kuroshio Extension.
  • Local Qnet and QEkman are response to the SST anomaly.

Other patterns

  • NAO/AO, PNA, ALE(WP)

Mixed Layer Depth

  • Seasonal cycle Temp & MLD
  • Winter MLD slightly too depth in NP and too shallow in N. Atlantic
  • Reemergence present
enso seasonal cycle
ENSO Seasonal Cycle

Timing of ENSO Events

Seasonal Cycle of ENSO Amplitude

sst and atmospheric teleconnections

ENSO in CCSM3

SST and Atmospheric Teleconnections
  • Compare T42 and T85 versions of CCSM3 (multi-century control integrations)
  • Compare CCSM3 with CCSM2 (T42 control integrations)
  • Compare CCSM3 T85 control with CAM3 T85 AMIP integration, 1950-2000
seasonal cycle of ocean temp and mld
Seasonal Cycle of Ocean Temp and MLD

Pacific:

35N-45N

165E-175W

Atlantic:

50N-60N

20W-40W

local lead lag correlations 42 52 n between sst and temp anomalies at the basepoint
Local Lead-lag Correlations 42º-52ºN between SST and Temp anomalies at the Basepoint

SST Lags

SST Leads

Basepoint: Aug-Sep, 55-85M

winter sst power spectrum
Winter SST Power Spectrum

Kuroshio Extension Index

Central North Pacific Index

~17 yr

subduction in the atlantic
Subduction in the Atlantic

POP

CCSM3

Trajectories based on annual averages on 25.4 surface

winter q ekman regressed on sst kuroshio extension index
Winter QEkman Regressed on SST Kuroshio Extension Index

SST regression

(Contour Interval: 10 W/m2/°C ; Shading: significant at 99 %)

winter q ekman regressed on sst kuroshio extension index low pass filter 10 yr
Winter QEkman regressed on SST Kuroshio Extension Index(Low-pass filter > 10 yr)

(Contour Interval: 10 W/m2/°C ; Shading: significant at 99 %)

  • Anomalous QEkman acts as a positive feedback to the SST anomalies.
arctic oscillation slp eof 1
Arctic Oscillation: SLP EOF 1

NCEP

CCSM3

31.5%

33.7%

summary
Summary
  • Leading EOFs of CCSM3 & CCSM2 winter SST have PDO-like horse-shoe pattern.
  • Robust decadal (16-20 yr) variability of SST along the Kuroshio Extension.
  • Ocean heat divergence driven by stochastic wind stress curl forcing is likely causing the decadal SST anomaly along the Kuroshio Extension.
  • Local Qnet and QEkman are response to the SST anomaly.
wind stress curl regressed on heat divergence in the kuroshio extension
Wind Stress Curl regressed on Heat Divergence in the Kuroshio Extension

Atmosphere

Leads

Simultaneous

Ocean

Leads

(Contour Interval : 5 x 10-9 N/m3 ; Shading : significant at 99 % ; Low-pass filter > 10 yr)

winter q net regression on sst kuroshio extension index
Winter QNET regression on SST Kuroshio Extension Index

QNET Leads (+1 Yr)

Simultaneous

QNET Lags (-1 Yr)

(Contour Interval: 10 W/m2/°C ; Shading: significant in 99 %)

correlation in the kuroshio extension geostrophic ekman heat divergence vs sst q net
Correlation in the Kuroshio Extension Geostrophic / Ekman Heat Divergence vs. SST / QNET

Geostrophic Heat Divergence

Ekman Heat Divergence

(Low-pass Filter > 10 yr)

correlation in the kuroshio extension total horizontal heat divergence vs sst q net
Correlation in the Kuroshio Extension Total Horizontal Heat Divergence vs. SST / QNET

(Low-pass Filter > 10 yr)

summary1
Summary
  • Many processes are simulated reasonably well:
    • e.g. Reemergence
    • NAO
  • Other processes while present differ somewhat from the real world
    • e.g. PNA
  • Hope these preliminary findings will motivate you to have a closer look.
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