Testing theories of baroclinic adjustment in the laboratory and in simple atmospheric models

The state of the Earth's climate can be viewed as resulting from a delicate balance between radiative forcing processes and the dynamical response of the system as it seeks to transport heat across the planet. Recent research has tended to focus on quantifying the radiative forcing processes and their associated uncertainties, and various factors (including those human-induced) leading to changes in the climate. But radiative forcing primarily constrains the energy throughput of the climate system and only indirectly influences key climate variables such as the mean surface temperature. Climate variables are also strongly affected by how efficiently heat is redistributed across the planet by dynamical processes in the atmosphere and oceans. These are intrinsically nonlinear, and are affected by internal feedbacks that are still not well understood. This leaves open such fundamental questions as: what determines the mean lapse rate in the extra-tropical atmosphere, and what determines the thermal contrast in the atmosphere between equator and poles or continents and oceans?

In this project, therefore, we will study the relevant dynamical processes in numerical model simulations, based on the Met Office ENDGame dynamical core, (a) in a configuration representing a novel laboratory analogue of the mid-latitude climate system in a real fluid under carefully controlled conditions (currently being investigated experimentally in Prof. Read's group in Oxford), and (b) in simplified global atmospheric models subject to idealized radiative and boundary forcing. Numerical model simulations will be carried out and (for (a)) compared with detailed measurements of the flow and thermal structure in the Oxford experiments. This will enable us to determine the efficiency of heat transfer linking convective and baroclinic regions in order to determine how transport efficiency scales with key parameters and how the flow itself determines the mean static stability. We will also be able to assess the conditions under which fully developed turbulent energy cascades emerge or may be suppressed. This will then be investigated (in (b)) over a range of atmospheric conditions, resolutions and convective parameterizations in the full ENDGame model with idealized forcing.