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Different warming patterns of tropical Pacific sea surface temperature projected by FGOALS-g2 and FGOALS-s2 under RCP8.5 |
ZHANG Li-Xia1,2,ZHOU Tian-Jun1,2 |
1State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
2Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China
3Joint Center for Global Change Studies (JCGCS), Beijing 100875, China |
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Abstract The different patterns of SST changes under the +8.5 W m?2 Representative Concentration Pathway (RCP8.5) projected by the latest two versions of the Flexible Global Ocean-Atmosphere-Land System model (FGOALS-g2 and FGOALS-s2; grid-point version 2 and spectral version 2, respectively), and the potential mechanisms for their formation are studied in this paper. The results show that, although both FGOALS-g2 and FGOALS-s2 project global warming patterns, FGOALS-g2 (FGOALS-s2) projects a La Ni?a-like (an El Ni?o-like) mean warming pattern with weakest (strongest) warming over the central (eastern) equatorial Pacific for 2081–2100 relative to 1986–2005 under RCP8.5. A mixed layer heat budget analysis shows that the projected tropical Pacific Ocean warming in both models is primarily caused by atmospheric forcing. The main differences in the heating terms contributing to the SST changes between the two models are seen in the downward longwave radiation and ocean forcing. The minimum SST warming over the equatorial Pacific in FGOALS-g2 is attributed to the local minimum heating of downward longwave radiation and maximum cooling of ocean forcing. In contrast, the maximum SST warming over the equatorial Pacific in FGOALS-s2 is due to the maximum warming of downward longwave radiation, and the contribution of ocean forcing is minor. The minimum SST warming over the equatorial Pacific in FGOALS-g2 emerges around the 2050s, before when the SST over the equatorial Pacific is warmer than that over the extra-equatorial Pacific. In FGOALS-s2, the SST difference shows a continuous increasing trend for 2006–2100. Further examination of the oceanic and atmospheric circulation changes is needed to reveal the process responsible for the longwave radiation and ocean forcing difference between the two models.
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Received: 20 August 2014
Revised: 06 February 2015
Accepted: 10 February 2015
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Corresponding Author:
ZHANG Li-Xia
E-mail: lixiazhang@mail.iap.ac.cn
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