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Abstract:
The tropical temperature in the free troposphere deviates from a theoretical moist-adiabat. The overall deviations are attributed to the entrainment of dry surrounding air. The deviations gradually approach zero in the upper troposphere, which we explain with a buoyancy-sorting mechanism: the height to which individual convective parcels rise depends on parcel buoyancy, which is closely tied to the impact of entrainment during ascent. In higher altitudes, the temperature is increasingly controlled by the convective parcels that are warmer and more buoyant because of weaker entrainment effects. We represent such temperature deviations from moist-adiabats in a clear-sky one-dimensional radiative-convective equilibrium model. Compared with a moist-adiabatic adjustment, having the entrainment-induced temperature deviations lead to higher clear-sky climate sensitivity. As the impact of entrainment depends on the saturation deficit, which increases with warming, our model predicts even more amplified surface warming from entrainment in a warmer climate. © 2021. The Authors.
