Toward the Dynamical Convergence on the Jet Stream in Aquaplanet AGCMs

Lu, Jian; Chen, Gang; Leung, L. Ruby; Burrows, D. A.; Yang, Qing; Sakaguchi, Kôichi; Hagos, Samson

doi:10.1175/jcli-d-14-00761.1

Cited by 44 publications

(54 citation statements)

References 56 publications

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“…In summary, combining information from the lower level JLI and the averaged 200‐hPa jet core amplitude, the 1/4deg simulations produce a jet stream with a poleward shift and weakening over the Atlantic and Pacific compared to 1deg, creating a more realistic zonal flow. This is also consistent with the result reported by Lu et al (), following their analysis of aqua‐planet simulations with a similar model.…”

Section: The General Circulation Of the Modelsupporting

confidence: 93%

Northern Hemisphere Blocking in ∼25‐km‐Resolution E3SM v0.3 Atmosphere‐Land Simulations

et al. 2019

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The fidelity of a prerelease Energy Exascale Earth System Model (E3SM) in reproducing atmospheric blocking is evaluated with ∼100‐ and ∼25‐km horizontal resolution within ensembles of simulations with Atmospheric Modeling Intercomparison Protocol‐type active atmosphere and land surface configurations. This evaluation is conducted via a hybrid bidimensional blocking index based on geopotential height. The lower‐resolution model correctly reproduces the spatial distribution of blocking frequency maxima over the Northern Hemisphere. However, it overestimates the blocking frequency over western North America, the Pacific Northeast, and Eastern Europe regions and largely underestimates blocking frequency over the North Atlantic. The high‐resolution model significantly reduces the bias over the North Pacific region, particularly over western North America, but the biases over the North Atlantic blocking sector mostly persist. A diagnosis of the mean flow reveals that the subtropical jet is displaced poleward in the high‐resolution model with a jet core speed that is generally more realistic. A time scale analysis of eddies suggests that synoptic eddies associated with the blocking events are increased in the high‐resolution configuration. The discrepancy between the models implies that both synoptic and low‐frequency eddies play significant roles in determining North Pacific blocking, whereas North Atlantic blocking is mainly driven by low‐frequency eddies. The characteristic time scale associated with blocking events is also investigated, and it shows that both model resolutions produce events that are overly persistent. However, the bias in the high‐resolution model is reduced, which reflects more efficient energy dispersion with higher resolution.

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Section: The General Circulation Of the Modelsupporting

confidence: 93%

Northern Hemisphere Blocking in ∼25‐km‐Resolution E3SM v0.3 Atmosphere‐Land Simulations

et al. 2019

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“…Novak et al (2015) investigated the role of meridional eddy heat flux in the tilt of the North Atlantic eddy-driven jet. This behaviour may partly explain the dominant equatorward bias of the jet stream in generations of global climate simulations with model resolutions much coarser than 50 km (Kidston and Gerber, 2010;Barnes and Polvani, 2013;Lu et al, 2015). Biases in the jet stream position have been found to correlate with the meridional shift of the jet position in a warmer climate (Kidston and Gerber, 2010).…”

Section: Extremes and Hydrological Cyclementioning

confidence: 92%

High Resolution Model Intercomparison Project (HighResMIP v1.0) for CMIP6

et al. 2016

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Abstract. Robust projections and predictions of climate variability and change, particularly at regional scales, rely on the driving processes being represented with fidelity in model simulations. The role of enhanced horizontal resolution in improved process representation in all components of the climate system is of growing interest, particularly as some recent simulations suggest both the possibility of significant changes in large-scale aspects of circulation as well as improvements in small-scale processes and extremes.However, such high-resolution global simulations at climate timescales, with resolutions of at least 50 km in the atmosphere and 0.25 • in the ocean, have been performed at relatively few research centres and generally without overall coordination, primarily due to their computational cost. Assessing the robustness of the response of simulated climate to model resolution requires a large multi-model ensemble using a coordinated set of experiments. The Coupled Model Intercomparison Project 6 (CMIP6) is the ideal framework within which to conduct such a study, due to the strong link to models being developed for the CMIP DECK experiments and other model intercomparison projects (MIPs).Increases in high-performance computing (HPC) resources, as well as the revised experimental design for CMIP6, now enable a detailed investigation of the impact of increased resolution up to synoptic weather scales on the simulated mean climate and its variability.The High Resolution Model Intercomparison Project (HighResMIP) presented in this paper applies, for the first time, a multi-model approach to the systematic investigation of the impact of horizontal resolution. A coordinated set of experiments has been designed to assess both a standard and an enhanced horizontal-resolution simulation in the atmosphere and ocean. The set of HighResMIP experiments is divided into three tiers consisting of atmosphere-only and coupled runs and spanning the period 1950-2050, with the possibility of extending to 2100, together with some additional targeted experiments. This paper describes the experimental set-up of HighResMIP, the analysis plan, the connection with the other CMIP6 endorsed MIPs, as well as the DECK and CMIP6 historical simulations. HighResMIP thereby focuses on one of the CMIP6 broad questions, "what are the origins and consequences of systematic model biases?", but we also discuss how it addresses the World Climate Research Program (WCRP) grand challenges.

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“…Solar forcing is fixed at perpetual equinox but includes diurnal variations. This aquaplanet configuration with prescribed SST has been used in many previous studies [e.g., Rauscher et al ., ; Zarzycki et al ., ] and in a series of simulations conducted with the MPAS dynamical core and CAM4 physics package [ Leung et al ., ; Lu et al ., ; O'Brien et al ., ; Yang et al ., ; Sakaguchi et al ., ] to investigate the effects of model resolution on various aspects of the large‐scale circulation. The global WRF aquaplanet simulation produces zonally symmetric large‐scale circulation features comparable to those of the MPAS aquaplanet simulations [e.g., Hagos et al ., ].…”

Section: Description Of Model and Experiments Designmentioning

confidence: 99%

Exploring the effects of a nonhydrostatic dynamical core in high‐resolution aquaplanet simulations

Yang

Leung

et al. 2017

JGR Atmospheres

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This study explores the impact of a nonhydrostatic dynamical core in high‐resolution regional climate simulations using an aquaplanet framework. The Weather Research and Forecasting (WRF) model is used to conduct simulations with both hydrostatic (H) and nonhydrostatic (NH) solvers at horizontal grid spacings (Δx) of 36, 12, and 4 km. The differences between the H and NH simulated precipitation (ΔP) are notable even at Δx = 12 km in the intertropical convergence zone and the transition region to the drier subtropics. At gray zone grid spacing (12 km and 4 km) over the tropics, ΔP is sensitive to whether a cumulus parameterization scheme is used or not. With an idealized Witch of Agnesi land mountain, differences in the precipitation and circulation (vertical velocity) between the H and NH simulations are significant even at Δx = 36 km in the tropics due largely to the strong feedbacks related to moist processes. The differences increase as the model grid spacing and mountain half width (a) are reduced, accompanied by a shift toward a more nonhydrostatic flow regime at a = 24 km. Latent heat release drastically enhances the differences between the NH and H simulations and extends the effect of nonhydrostatic dynamics to a broader region over the mountain and downstream over the tropics. Overall, differences exist between H and NH simulations even at resolutions between 12 and 36 km, but the differences are sensitive to the representations of moist physics and other features such as horizontal diffusion used in the WRF model.

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Toward the Dynamical Convergence on the Jet Stream in Aquaplanet AGCMs

Cited by 44 publications

References 56 publications

Northern Hemisphere Blocking in ∼25‐km‐Resolution E3SM v0.3 Atmosphere‐Land Simulations

Northern Hemisphere Blocking in ∼25‐km‐Resolution E3SM v0.3 Atmosphere‐Land Simulations

High Resolution Model Intercomparison Project (HighResMIP v1.0) for CMIP6

Exploring the effects of a nonhydrostatic dynamical core in high‐resolution aquaplanet simulations

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