CCA1: Lapse rate feedback

In low latitudes, the lapse rate is governed by a moist adiabat. A warmer climate implies that the surface warms less than the free troposphere. This reduces the greenhouse effect – a negative feedback. In the Arctic, in turn, vertical mixing is hampered by a stable atmosphere and climate models show that the surface warms more than the free troposphere. The stronger lapse rate implies a stronger greenhouse effect – a positive feedback.

• Investigate quantitatively the components of the lapse rate feedback,
• To verify and improve its representation in climate models exploiting observations,
• To quantify its contribution to Arctic amplification

• Which processes determine the surface energy budget (link to CCA2)?
• How does the vertical mixing and the inversion strength change in the Arctic? What is the role of cloud-top radiative cooling (e.g., in response to the increase in liquid phase) (link to CCA3)?
• How does the free-tropospheric temperature change and what governs changes in radiative cooling and in advective heating (link to CCA4)?

• Combine results from observations and modelling across scales in the conceptual radiative feedback framework by evaluating and revising relevant process descriptions in the ICON climate model.
• Assess sensitivity of surface and free-tropospheric temperature to key Arctic climate change drivers from observations.
• Process-oriented assessment of data will be applied for model evaluation, where discrepancies between simulations and observations are identified.