The ICON atmosphere model (ICON-A) constitutes the atmospheric component of the ICON Earth system model (ICON-ESM). ICON-A combines the non-hydrostatic dynamical core, which is equally used in the operational numerical weather prediction at the German Weather Service and in large eddy simulations, with the parameterization package originating from the ECHAM6 atmosphere model. The physics is adapted for the vertical coordinate system and time stepping scheme of the ICON dynamical core.

The standard setup of ICON-A makes use of the R2B4 grid with a mean resolution of 160 km and a 47 level vertical grid extending upward to 80 km height, which is overall comparable to the popular low resolution "LR" setup of ECHAM6.

The panel shows typical climatological biases in four regions of ICON-A and two ECHAM6 versions for AMIP experiments over 30 years (1979 - 2008). ECHAM6.1 was used for CMIP5 and ECHAM6.3 is used for CMIP6. Overall the biases of ICON-A are comparable to those of ECHAM6.3 and better than those of ECHAM6.1.