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ABOUT CIRCULATES

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Project Duration

CIRCULATES will run from 1/2/2020 – 31/1/2024.

Project Aims

Summary

The Circulation, Clouds and Climate Sensitivity project (CIRCULATES) will combine new observations with a hierarchy of model simulations to significantly advance our understanding and quantification of the radiative feedbacks associated with tropical and subtropical low clouds. These clouds have been consistently identified by decades of assessments as the most important source of uncertainty affecting radiative feedback and climate sensitivity. Our project focuses on the coupling between clouds, radiation, the large-scale circulation and surface and boundary layer processes. The hierarchy of model simulations we will use range from high-resolution large eddy simulations and cloud resolving models, through idealised configurations of a global model, to full-complexity climate models used in international assessments of climate sensitivity. The project will test new ways of parameterising cloud processes by placing constraints we discover from high-resolution simulations and new remote sensing observations directly inside the idealised global model. Thus, we will provide a direct link between the uncertainty in physical processes and the uncertainty in cloud radiative feedbacks and climate sensitivity. The new understanding developed will then be used to derive a collection of new process-based metrics for constraining projections from full-complexity models and for use in model development. Such metrics may be combined with similar metrics of the radiative effects of other clouds to quantify and reduce uncertainty in climate sensitivity in round 2 of the Uncertainty in Climate Sensitivity due to Clouds programme. Our specific objectives, which map directly onto the 4 work packages (WPs), are as follows:

Objectives

O1) Quantify the roles of circulation and surface coupling in tropical and subtropical cloud feedback and climate sensitivity using high-resolution cloud resolving models (CRMs) and large eddy simulations (LES)

O2) Assess the coupling between cloud, radiation, circulation, and patterns of sea surface temperature variability using satellite observations and modelling of the recent period.

O3) Use information from CRMs, LES and observations to develop and modify cloud and convection parameterisation schemes for general circulation models (GCMs) used to predict future climate change and hence assess the impact of convective-scale and microphysical uncertainties on estimates of cloud feedback and climate sensitivity

O4) Develop multiple process-based metrics to be used in quantifying and reducing uncertainty in tropical and low cloud feedbacks in multi-model ensembles. Our outputs will be made available not only through publication but will also contribute directly to model development through the project’s strong involvement with the Met Office and produce metrics that other researchers can use through the ESM Val Tool framework (Eyring et al., 2016a).

CIRCULATES will be delivered in four distinct but interacting work packages: High-resolution modelling (WP1) and analysis of observations (WP2) will feed into global GCM modelling (WP3), informing climate projection uncertainty quantification and metrics for model development (WP4).

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