The Green's Function Model Intercomparison Project (GFMIP) Protocol

Abstract

The atmospheric Green's function method is a technique for modeling the response of the atmosphere to changes in the spatial field of surface temperature. While early studies applied this method to changes in atmospheric circulation, it has also become an important tool to understand changes in radiative feedbacks due to evolving patterns of warming, a phenomenon called the “pattern effect.” To better study this method, this paper presents a protocol for creating atmospheric Green's functions to serve as the basis for a model intercomparison project, GFMIP. The protocol has been developed using a series of sensitivity tests performed with the HadAM3 atmosphere‐only general circulation model, along with existing and new simulations from other models. Our preliminary results have uncovered nonlinearities in the response of the atmosphere to surface temperature changes, including an asymmetrical response to warming versus cooling patch perturbations, and a change in the dependence of the response on the magnitude and size of the patches. These nonlinearities suggest that the pattern effect may depend on the heterogeneity of warming as well as its location. These experiments have also revealed tradeoffs in experimental design between patch size, perturbation strength, and the length of control and patch simulations. The protocol chosen on the basis of these experiments balances scientific utility with the simulation time and setup required by the Green's function approach. Running these simulations will further our understanding of many aspects of atmospheric response, from the pattern effect and radiative feedbacks to changes in circulation, cloudiness, and precipitation.

Factors determining tropical upper-level cloud radiative effect in the radiative-convective equilibrium framework

“…The response of climate to localized tropical SST perturbations demonstrates considerable non-linearity, highlighting the importance of both the spatial pattern and magnitude of SST changes 43 . This pattern effect, therefore, should be carefully understood addressing the drivers of the amplitude and sign of SST perturbations 44 , 45 . Indeed, for the analysis on the relationship between TOA radiative fluxes and SST, there was disparities by the selection of domain 14 .…”

Potential Near‐Term Wetting of the Southwestern United States if the Eastern and Central Pacific Cooling Trend Reverses

“…We developed a precipitation Green's function (GF P ) to identify which SST regions influence SWUS (32°-40°N, 124°-105°W) precipitation (e.g., Alessi & Rugenstein, 2023b;Bloch-Johnson et al, 2024;Y. Dong et al, 2019;Zhang et al, 2023;Zhou et al, 2017).…”