TY - JOUR
T1 - The aqua-planet experiment (APE)
T2 - CONTROL SST simulation
AU - Blackburn, Michael
AU - Williamson, David L.
AU - Nakajima, Kensuke
AU - Ohfuchi, Wataru
AU - Takahashi, Yoshiyuki O.
AU - Hayashi, Yoshi Yuki
AU - Nakamura, Hisashi
AU - Ishiwatari, Masaki
AU - McGregor, John L.
AU - Borth, Hartmut
AU - Wirth, Volkmar
AU - Frank, Helmut
AU - Bechtold, Peter
AU - Wedi, Nils P.
AU - Tomita, Hirofumi
AU - Satoh, Masaki
AU - Zhao, Ming
AU - Held, Isaac M.
AU - Suarez, Max J.
AU - Lee, Myong In
AU - Watanabe, Masahiro
AU - Kimoto, Masahide
AU - Liu, Yimin
AU - Wang, Zaizhi
AU - Molod, Andrea
AU - Rajendran, Kavirajan
AU - Kitoh, Akio
AU - Stratton, Rachel
PY - 2013
Y1 - 2013
N2 - Climate simulations by 16 atmospheric general circulation models (AGCMs) are compared on an aqua-planet, a water-covered Earth with prescribed sea surface temperature varying only in latitude. The idealised configuration is designed to expose differences in the circulation simulated by different models. Basic features of the aqua-planet climate are characterised by comparison with Earth. The models display a wide range of behaviour. The balanced component of the tropospheric mean flow, and mid-latitude eddy covariances subject to budget constraints, vary relatively little among the models. In contrast, differences in damping in the dynamical core strongly influence transient eddy amplitudes. Historical uncertainty in modelled lower stratospheric temperatures persists in APE. Aspects of the circulation generated more directly by interactions between the resolved fluid dynamics and parameterized moist processes vary greatly. The tropical Hadley circulation forms either a single or double inter-tropical convergence zone (ITCZ) at the equator, with large variations in mean precipitation. The equatorial wave spectrum shows a wide range of precipitation intensity and propagation characteristics. Kelvin mode-like eastward propagation with remarkably constant phase speed dominates in most models. Westward propagation, less dispersive than the equatorial Rossby modes, dominates in a few models or occurs within an eastward propagating envelope in others. The mean structure of the ITCZ is related to precipitation variability, consistent with previous studies. The aqua-planet global energy balance is unknown but the models produce a surprisingly large range of top of atmosphere global net flux, dominated by differences in shortwave reflection by clouds. A number of newly developed models, not optimised for Earth climate, contribute to this. Possible reasons for differences in the optimised models are discussed. The aqua-planet configuration is intended as one component of an experimental hierarchy used to evaluate AGCMs. This comparison does suggest that the range of model behaviour could be better understood and reduced in conjunction with Earth climate simulations. Controlled experimentation is required to explore individual model behaviour and investigate convergence of the aqua-planet climate with increasing resolution.
AB - Climate simulations by 16 atmospheric general circulation models (AGCMs) are compared on an aqua-planet, a water-covered Earth with prescribed sea surface temperature varying only in latitude. The idealised configuration is designed to expose differences in the circulation simulated by different models. Basic features of the aqua-planet climate are characterised by comparison with Earth. The models display a wide range of behaviour. The balanced component of the tropospheric mean flow, and mid-latitude eddy covariances subject to budget constraints, vary relatively little among the models. In contrast, differences in damping in the dynamical core strongly influence transient eddy amplitudes. Historical uncertainty in modelled lower stratospheric temperatures persists in APE. Aspects of the circulation generated more directly by interactions between the resolved fluid dynamics and parameterized moist processes vary greatly. The tropical Hadley circulation forms either a single or double inter-tropical convergence zone (ITCZ) at the equator, with large variations in mean precipitation. The equatorial wave spectrum shows a wide range of precipitation intensity and propagation characteristics. Kelvin mode-like eastward propagation with remarkably constant phase speed dominates in most models. Westward propagation, less dispersive than the equatorial Rossby modes, dominates in a few models or occurs within an eastward propagating envelope in others. The mean structure of the ITCZ is related to precipitation variability, consistent with previous studies. The aqua-planet global energy balance is unknown but the models produce a surprisingly large range of top of atmosphere global net flux, dominated by differences in shortwave reflection by clouds. A number of newly developed models, not optimised for Earth climate, contribute to this. Possible reasons for differences in the optimised models are discussed. The aqua-planet configuration is intended as one component of an experimental hierarchy used to evaluate AGCMs. This comparison does suggest that the range of model behaviour could be better understood and reduced in conjunction with Earth climate simulations. Controlled experimentation is required to explore individual model behaviour and investigate convergence of the aqua-planet climate with increasing resolution.
KW - Comparison of atmospheric general circulation models (GCMS)
KW - Global energy buget
KW - Idealized model configuration
KW - Precipitation
KW - Tropical wave spectrum
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U2 - 10.2151/jmsj.2013-A02
DO - 10.2151/jmsj.2013-A02
M3 - Article
AN - SCOPUS:84886797645
SN - 0026-1165
VL - 91
SP - 17
EP - 56
JO - Journal of the Meteorological Society of Japan
JF - Journal of the Meteorological Society of Japan
IS - 1 A
ER -