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

Robust projections and predictions of climate vari-
ability 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 cli-
mate system is of growing interest, particularly as some re-
cent simulations suggest both the possibility of significant
changes in large-scale aspects of circulation as well as im-
provements in small-scale processes and extremes.
However, such high-resolution global simulations at cli-
mate timescales, with resolutions of at least 50 km in the at-
mosphere 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. As-
sessing 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) re-
sources, 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 atmo-
sphere and ocean. The set of HighResMIP experiments is di-
vided into three tiers consisting of atmosphere-only and cou-
pled runs and spanning the period 1950–2050, with the pos-
sibility 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 Pro-
gram (WCRP) grand challenges.