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Simulation of the Equatorially Asymmetric Mode of the Hadley Circulation in CMIP5 Models

 

FENG Juan^1,2,3, LI Jianping^1,3, ZHU Jianlei², LI Fei⁴, and SUN Cheng^1,3

 

1 College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875

2 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,

Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029

3 Joint Center for Global Change Studies, Beijing 100875

4 Department of Lower Atmosphere Observation Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029

 

ABSTRACT

The tropical Hadley circulation (HC) plays an important role in influencing the climate in the tropics and extra-tropics. The realism of the climatological characteristics, spatial structure, and temporal evolution of the long-term variation of the principal mode of the annual mean HC (i.e., the equatorially asymmetric mode, EAM) was examined in model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The results showed that all the models are moderately

successful in capturing the HC’s climatological features, including the spatial pattern, meridional extent, and intensity, but not the spatial or temporal variation of the EAM. The possible reasons for the poor simulation of the long-term variability of the

EAM were explored. None of the models can successfully capture the differences in the warming rate between the tropical Southern Hemisphere (SH) and Northern Hemisphere (NH), which is considered to be an important driver for the variation of

the AM. Most of the models produce a faster warming in the NH than in the SH, which is the reverse of the observed trend. This leads to a reversed trend in the meridional gradient between the SH and NH, and contributes to the poor simulation of

EAM variability. Thus, this aspect of the models should be improved to provide better simulations of the variability of the HC. This study suggests a possible reason for the poor simulation of the HC, which may be helpful for improving the skill of

the CMIP5 models in the future.

KEY WORDS: tropical Hadley circulation, equatorially asymmetric mode, CMIP5, sea surface temperature

PUBLISHED BY: Advances in Atmospheric Sciences, 2015,32(8), 1129-1142, DOI:10.1007/s00376-015-4157-0.

SOURCE: http://link.springer.com/article/10.1007/s00376-015-4157-0