Abstract
AbstractVariability of atmospheric water vapour is the most important climate feedback in present climate models. Thus, it is of crucial importance to understand the sensitivity of water vapour to model attributes, such as physical parametrizations and resolution. Here we attempt to determine the minimum vertical resolution necessary for accurate prediction of water vapour.To address this issue, we have run two single‐column models to tropical radiative—convective equilibrium states and have examined the sensitivity of the equilibrium profiles to vertical resolution. Both column models produce reasonable equilibrium states of temperature and moisture.Convergence of the profiles was achieved in both models using a uniform vertical resolution of around 25 hPa. Coarser resolution leads to significant errors in both the water vapour and temperature profiles, with a resolution of 100 hPa proving completely inadequate. However, fixing the boundary‐layer resolution and altering only the free‐tropospheric resolution significantly reduces sensitivity to vertical resolution in one of the column models, in both water and temperature, highlighting the importance of resolving boundary‐layer processes. Additional experiments show that the height of the simulated tropopause is sensitive to upper‐tropospheric vertical resolution.At resolutions higher than 33 hPa, one of the models developed a high degree of vertical structure in the vapour profile, resulting directly from the complex array of microphysical processes included in the stratiform cloud parametrization, some of which were only resolved at high resolutions. This structure was completely absent at lower resolutions, casting some doubt on the approach of using relatively complicated cloud schemes at low vertical resolutions.
Published Version
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