Convection Parameterization, Tropical Pacific Double ITCZ, and Upper-Ocean Biases in the NCAR CCSM3. Part II: Coupled Feedback and the Role of Ocean Heat Transport
Open Access
- 1 February 2010
- journal article
- Published by American Meteorological Society in Journal of Climate
- Vol. 23 (3), 800-812
- https://doi.org/10.1175/2009jcli3109.1
Abstract
This study investigates the coupled atmosphere–ocean feedback and the role of ocean dynamic heat transport in the formation of double ITCZ over the tropical Pacific in the NCAR Community Climate System Model, version 3 (CCSM3) and its alleviation when a revised Zhang–McFarlane (ZM) convection scheme is used. A hierarchy of coupling strategy is employed for this purpose. A slab ocean model is coupled with the atmospheric component of the Community Atmosphere Model, version 3 (CAM3) to investigate the local feedback between the atmosphere and the ocean. It is shown that the net surface energy flux differences in the southern ITCZ region between the revised and original ZM scheme seen in the stand-alone CAM3 simulations can cool the SST by up to 1.5°C. However, the simulated SST distribution is very sensitive to the prescribed ocean heat transport required in the slab ocean model. To understand the role of ocean heat transport, the fully coupled CCSM3 model is used. The analysis of CCSM3 simulations shows that the altered ocean dynamic heat transport when the revised ZM scheme is used is largely responsible for the reduction of SST bias in the southern ITCZ region, although surface energy flux also helps to cool the SST in the first few months of the year in seasonal variation. The results, together with those from Part I, suggest that the unrealistic simulation of convection over the southern ITCZ region in the standard CCSM3 leads to the double-ITCZ bias through complex coupled interactions between atmospheric convection, surface winds, latent heat flux, cloud radiative forcing, SST, and upper-ocean circulations. The mitigation of the double-ITCZ bias using the revised ZM scheme is achieved by altering this chain of interactions.Keywords
This publication has 19 references indexed in Scilit:
- The Double-ITCZ Problem in IPCC AR4 Coupled GCMs: Ocean–Atmosphere Feedback AnalysisJournal of Climate, 2007
- Precipitation Characteristics in Eighteen Coupled Climate ModelsJournal of Climate, 2006
- An Improved In Situ and Satellite SST Analysis for ClimateJournal of Climate, 2002
- An Improved Coupled Model for ENSO Prediction and Implications for Ocean Initialization. Part I: The Ocean Data Assimilation SystemMonthly Weather Review, 1998
- IntroductionPublished by Springer Science and Business Media LLC ,1998
- The Seasonal Cycle over the Tropical Pacific in Coupled Ocean–Atmosphere General Circulation ModelsMonthly Weather Review, 1995
- An Ocean Analysis System for Seasonal to Interannual Climate StudiesMonthly Weather Review, 1995
- A Global Oceanic Data Assimilation SystemJournal of Physical Oceanography, 1989
- Diurnal to decadal global forcing for ocean and sea-ice models: The data sets and flux climatologies
- Description of the NCAR Community Atmosphere Model (CAM 3.0)