Toward Eliminating the Double Inter-Tropical Convergence Zone and Improving El Nino/Southern Oscillation Simulation in the NCAR Community Climate System Model Version 3 (CCSM3)

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

This is a continuation project with a focus on mitigating the double Inter-Tropical Convergence Zone (ITCZ) problem and to improve the simulation of El Nino and Southern Oscillation (ENSO) in the fully coupled NCAR Community Climate System Model, CCSM3. These are amongst the most fundamental deficiencies in CCSM3. The basic research tools used are the CCSM3 and the improved Zhang-McFarlane convection scheme. The coupled model integrations with improved convection scheme will be analyzed to examine the improvement of ITCZ and ENSO simulations. Short term (=10 years) numerical experiments with both the original and improved convection scheme will be conducted to understand the interaction between convection and the large-scale circulation, and the role of convection parameterization in the elimination of double ITCZ. The ENSO simulation will focus on the role of the zonal wind stress off the equatorial region in relation to the improved simulation of convection in the Pacific and the role of enhanced Madden-Julian Oscillation (MJO) variability in increasing the periodicity of the simulated ENSO cycle. Intellectual merit: The PI will (1) Improve the simulation of the ITCZ precipitation to eliminate the double ITCZ problem in CCSM3, (2) Improve scientific understanding of the role of convection parameterization in the double ITCZ problem through carefully designed numerical experiments, (3) Improve the simulation of ENSO periodicity, and (4) Find the causes of the improvements, in particular, the roles of surface wind stress and enhanced MJO simulation in the CCSM3. Completion of this work will offer new insights into: (1) Ways the new cumulus convection parameterization will result in an improved simulation of ITCZ, and (2) Processes that results in the mitigation of the most fundamental model deficiencies in CCSM3 Broader impacts: The research will lead to an improved climate system model that is being used worldwide by the climate research communities for a wide spectrum of climate change research. It also provides learning experiences and training for a graduate student.