New Evidence on the Importance of Cloud

Representations for Climate Simulations

Cristina StanCenter for Ocean-Land-Atmosphere Studies, COLA

AcknowledgementMarat Khairoutdinov, Stony Brook UniversityCharlotte DeMott, Colorado State UniversityV. Krishnamurthy, COLA/GMU

Common biases in the current generation of CGCMs

• Second spurious Inter-Tropical Convergence Zone (ITCZ) south of the equator in the eastern Pacific

• Errors in the precipitation distribution over the Indo-Pacific Warm Pool with An excess of precipitation over the western Indian Ocean and Maritime

Continent Dry biases over Bay of Bengal

• Misrepresentation of the MJO Does not occur often enough Underestimation of the strength and coherence of convection and wind

variability Life cycle

• ENSO with Unrealistic amplitude Period that is too long or too short Symmetric structure of the warm-cold events

• Weak ENSO-monsoon teleconnection

Models Configuration

SP-CCSM CCSM3.0

AtmosphericModel

Horiz. Res. T42 (sld) T42 (sld)

Vert. levels 30 26

Deep conv. CRM ZM

Shallow conv. CRM Hack

Ocean Model

Horiz. Res. gx3v5 gx3v5

Vert. levels 25 25

Sea-Ice Model

CSIM4 CSIM4

Land Model CLM3.0 CLM3.0

Precipitation Simulation Winter Climatology

CCSM

SPCCSMOBS

SPCAM

Precipitation Simulation Summer Climatology

CCSM

SPCCSMOBS

SPCAM

CCSM SP-CCSM OBS

MJO Simulation(Summer, 20-100 bandpass )

SP-CCSM CCSM

OBS

SP-CCSM CCSM

MJO Simulation (Winter, 20-100 bandpass )

OBS

ENSO SimulationNiño 3.4 (5S-5N,170W-120W)

OBS

SP-CCSM

CCSM

ENSO SimulationNiño 3.4 (5S-5N,170W-120W)

48 months

30 months

24 months

OBS

SSTA Regression with Niño3.4

OBS

SP-CCSM

CCSM

ENSO-Monsoon RelationshipIMR (JJA), SSTA(DJF-1)

SP-CCSM

OBS

CCSM

Annual Implied Northward Ocean Heat Transport

OBSSP-CCSMCCSM

Conclusions

• On interannual time-scales, SP-CCSM produces an improved ENSO with irregular frequency of events;

• On seasonal time-scales, SP-CCSM simulates a realistic relationship between the Indian summer monsoon and the sea surface temperature (SST) anomaly during the winter season following the monsoon especially for the eastern Pacific. In the western Pacific, SP-CCSM shows a reversed correlation between the SST anomaly and monsoon.

• On intraseasonal time-scales, SP-CCSM captures the 20-100 day bandpass variability of precipitation and atmospheric circulation. Compared to the control simulation, the SP-CCSM produces a much more robust and realistic Madden-Julian Oscillation (MJO).

Future Work

• Use SP-CCSM as prediction tool

• Couple the new version of SP-CAM with an ocean with higher resolution.