Chou, C., J. D. Neelin, J.-Y. Tu, and C.-T. Chen, 2006:
J. Climate, 19 (17), 4207-4223.
Paper (PDF 2 MB)
© Copyright 2006 by the American Meteorological Society.
Abstract. Mechanisms of global warming impacts on regional tropical precipitation are examined in a coupled atmosphere-ocean general circulation model (ECHAM4/OPYC3). The pattern of the regional tropical precipitation changes, once established, tends to persist, growing in magnitude as greenhouse gases increase. The sulfate aerosol induces regional tropical precipitation anomalies similar to the greenhouse gases but with opposite sign, thus reducing the early signal. Evidence for two main mechanisms, the upped-ante and the anomalous gross moist stability (M') mechanisms (previously proposed in an intermediate complexity model), is found in this more comprehensive coupled general circulation model. Preferential moisture increase occurs in convection zones. The upped-ante mechanism signature of dry advection from non-convective regions is found in tropical drought regions on the margins of convection zones. Here advection in both the atmospheric boundary layer and lower free troposphere are found to be important with an additional contribution from horizontal temperature transport in some locations. The signature of the M' mechanism---moisture convergence due to increased moisture in regions of large mean vertical motion---enhances precipitation within strong convective regions. Ocean dynamical feedbacks can be assessed by net surface flux, the main example being the El Niño-like shift of the equatorial Pacific convection zone. Cloud-radiative feedbacks are found to oppose precipitation anomalies over ocean regions.
Citation. Chou, C., J. D. Neelin, J.-Y. Tu, and C.-T. Chen, 2006: Regional tropical precipitation change mechanisms in ECHAM4/OPYC3 under global warming. J. Climate, 19 (17), 4207-4223.
Acknowledgments. We thank the Global Climate Modeling group at the Max Planck Institute for Meteorology, Hamburg, Germany, especially Dr. E. Roeckner and Ms. Monika Esch, for providing access to data from their simulations. The corresponding author particularly thanks Dr. Jia-Yuh Yu for useful comments. This work was supported under National Science Council grant 93-2111-M-001-001, the National Science Foundation grant ATM-0082529 and National Oceanic and Atmospheric Administration grant NA16GP2003. This is the University of California, Los Angeles, Institute of Geophysics and Planetary Physics contribution number 6243.