Abstract
Abstract. General circulation models (GCMs) are routinely run under Atmospheric Modelling Intercomparison Project (AMIP) conditions with prescribed sea surface temperatures (SSTs) and sea ice concentrations (SICs) from observations. These AMIP simulations are often used to evaluate the role of the land and/or atmosphere in causing the development of systematic errors in such GCMs. Extensions to the original AMIP experiment have also been developed to evaluate the response of the global climate to increased SSTs (prescribed) and carbon dioxide (CO2) as part of the Cloud Feedback Model Intercomparison Project (CFMIP). None of these international modelling initiatives has undertaken a set of experiments where the land conditions are also prescribed, which is the focus of the work presented in this paper. Experiments are performed initially with freely varying land conditions (surface temperature, and soil temperature and moisture) under five different configurations (AMIP, AMIP with uniform 4 K added to SSTs, AMIP SST with quadrupled CO2, AMIP SST and quadrupled CO2 without the plant stomata response, and increasing the solar constant by 3.3 %). Then, the land surface temperatures from the free land experiments are used to perform a set of “AMIP prescribed land” (PL) simulations, which are evaluated against their free land counterparts. The PL simulations agree well with the free land experiments, which indicates that the land surface is prescribed in a way that is consistent with the original free land configuration. Further experiments are also performed with different combinations of SSTs, CO2 concentrations, solar constant and land conditions. For example, SST and land conditions are used from the AMIP simulation with quadrupled CO2 in order to simulate the atmospheric response to increased CO2 concentrations without the surface temperature changing. The results of all these experiments have been made publicly available for further analysis. The main aims of this paper are to provide a description of the method used and an initial validation of these AMIP prescribed land experiments.
Highlights
In order to evaluate the atmosphere and land modules of general circulation models (GCMs), simulations can be run under Atmospheric Model Intercomparison Project (AMIP) specifications (Gates, 1992; Gates et al, 1999)
In addition to the standard AMIP experiments, quadrupled CO2 and spatially uniform 4 K sea surface temperatures (SSTs) increase experiments were incorporated as part of CMIP5 by the Cloud Feedback Model Intercomparison Project (CFMIP; Bony et al, 2011)
While the AMIP experiments described above are designed to investigate the response of the land and the atmosphere to the imposed SST and CO2 conditions, there is scope to further isolate the response of the atmosphere by prescribing the land conditions too
Summary
In order to evaluate the atmosphere and land modules of general circulation models (GCMs), simulations can be run under Atmospheric Model Intercomparison Project (AMIP) specifications (Gates, 1992; Gates et al, 1999) Both sea surface temperatures (SSTs) and sea ice concentrations (SICs) are prescribed from observations over some. Ackerley et al.: AMIP prescribed land reference period (e.g. 1979–2014 in the Coupled Model Intercomparison Project phase 6 – CMIP6 – experiment; see Eyring et al, 2016) with the atmosphere and land allowed to respond freely to the SST and SIC field Such AMIP simulations help to understand the role of the atmosphere and/or land in the development of model errors.
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