Can We Use Single‐Column Models for Understanding the Boundary Layer Cloud‐Climate Feedback?

Abstract

AbstractThis study explores how to drive Single‐Column Models (SCMs) with existing data sets of General Circulation Model (GCM) outputs, with the aim of studying the boundary layer cloud response to climate change in the marine subtropical trade wind regime. The EC‐EARTH SCM is driven with the large‐scale tendencies and boundary conditions as derived from two different data sets, consisting of high‐frequency outputs of GCM simulations. SCM simulations are performed near Barbados Cloud Observatory in the dry season (January–April), when fair‐weather cumulus is the dominant low‐cloud regime. This climate regime is characterized by a near equilibrium in the free troposphere between the long‐wave radiative cooling and the large‐scale advection of warm air. In the SCM, this equilibrium is ensured by scaling the monthly mean dynamical tendency of temperature and humidity such that it balances that of the model physics in the free troposphere. In this setup, the high‐frequency variability in the forcing is maintained, and the boundary layer physics acts freely. This technique yields representative cloud amount and structure in the SCM for the current climate. Furthermore, the cloud response to a sea surface warming of 4 K as produced by the SCM is consistent with that of the forcing GCM.