CMIP7 Experiment

We are developing an update to the HighResMIPv1 experimental design towards CMIP7. The main differences are in the atmosphere-only simulations, and extending the coupled future simulations to 2100. The exact value for “present” in the following is undecided and will be influenced by CMIP7, likely around 2022/23.

HighResMIP CMIP7 protocol

The HighResMIPv2 protocol towards CMIP7 is being developed, as well as the new output requirements for the Data Request. The details are still under discussion, with an aim for a full proposal by end-2023. Below is a short outline of the current proposal, with an illustration at the bottom.

Tier 1a: Forced-atmosphere runs 1980-present

Experiment name: highresSST-present: Using ESA CCI forcing for SST and sea-ice (daily, 0.05 degree, updated to 2022 currently).

Tier 1b: Coupled control runs 1950-2050

Spin-up: 50 year spin-up from EN4 ocean climatology with constant 1950’s forcing. Experiment name: spinup-1950
Control: 100 years with 1950’s forcing. Experiment name: control-1950

Tier 2: Coupled historic runs 1950-present.

Historic: 1950-present with historic forcing. Experiment name: hist-1950

Tier 3a: Forced-atmosphere warming levels

Forced atmosphere simulations at different warming levels, including +4K experiment. Experiment name: highresSST-warming-levels

Tier 3b: Coupled future present-2100

Future: present-2100 with scenario forcing. Experiment name: highres-future-sspxxx

Tier 4: One year experiment

A one year experiment (exact year TBD), to link with other communities. Experiment name: highres-one-year-xxxx

Motivation of these four Tiers

Focus of HighResMIP is on the 1950-2100 period (Tier 2) for coupled simulations - extended from 2050 due to demand and feedback from HighResMIPv1. This period includes significant past changes and the time horizon for the future is relevant for decision makers.

The division of the forced-atmosphere (AMIP-style) runs in Tier 1 and Tier 3 is to enable NWP centers to participate. It has been made shorter in order to use higher resolution SST/sea-ice forcings, and also to make it possible to use higher resolutions/produce more ensemble members. The “future climate” has been made explicitly idealised by using warming levels, either constant addition to SST (+4K to link to CMIP metrics), or patterned SST/reduced sea-ice at e.g. +2K, +3K.

Resolution: Atmosphere sub-50 km (ideally 10-25km); Ocean sub-0.25 degree (ideally eddy-rich)

Experiments are ideally repeated with standard resolution (but not enforced). Any lower resolution version would ideally link to CMIP DECK runs, but it is understood that higher resolution configurations take longer to develop, so older configurations are also encouraged.

HighResMIP philosophy: If tuning is necessary it should be well documented to ensure any improvements are due to process representation.

Further proposed targeted experiments

Further sensitivity experiments are possible and await suggestions:

Schematic of HighResMIP CMIP7 simulation design