An Update on Testing Modifications in CAM3 Convection Parameterization:

Results from Coupled Model Simulations

Guang Zhang

Scripps Institution of Oceanography

La Jolla, California

Collaborator: Houjun Wang

What Improvements Have Been Made in CAM3?

• Reduced double ITCZ bias

• Increased MJO variability

• Arabian Desert summer precipitation gone

• Increased western Pacific summer monsoon precipitation

Outline

• Two 10-yr-long simulations, one for control, and one for modified convection scheme

• ITCZ/SST Simulation

• MJO

• Global Budgets

Variable CAM3_new OBS data CAM3

FLUT_CERES 235.213 238.933 234.659

FLUT_ERBE 235.213 233.946 234.659

LWCF_CERES 28.588 27.129 29.634

LWCF_ERBE 28.588 30.355 29.634

PRECT_GPCP 2.817 2.607 2.827

PREH2O_NVAP 24.646 24.575 24.449

SWCF_CERES -55.862 -49.176 -54.932

SWCF_ERBE -55.862 -54.163 -54.932

Variable CCSM3_new OBS data CCSM3

FLNT 232.081 238.933 233.244

LWCF 29.097 27.129 29.060

PRECT_GPCP 2.731 2.607 2.782

PREH2O_NVAP 24.427 24.575 23.726

SWCF -55.186 -49.176 -54.282

CAM3

CCSM3

Summary

• Coupled simulation using CCSM3 with the modified Zhang-McFarlane scheme shows several important improvements over the standard CCSM3: Double ITCZ is mitigated; SST biases in the cold tongue and south of the equator are reduced; MJO simulation is improved similar to what was seen in CAM3.

• TOA radiation balance is well maintained.

http://www-cas.ucsd.edu/~zhang/ncar_diag/ccsm3rzm-ccsm3std/index.html