EUREC4A-UK is a programme of observational and modelling research which aims to study the detailed aerosol and cloud processes in the life cycle of shallow trade cumulus clouds and the two-way interactions between the cloud processes and the large-scale dynamics. The different responses of these clouds to warming in global climate models (GCM) explain most of the inter-model differences, yet the physics of these responses remains poorly constrained. The programme is focussed on the participation of UK scientists and the BAS Twin Otter aircraft in EUREC4A (Elucidating the Role of Clouds-Circulation Coupling in Climate). EUREC4A is a coordinated international campaign that aims to address the current lack of understanding of the processes controlling the response of trade-wind cumulus clouds to changing environmental conditions in a warmer climate. The goal of EUREC4A is to examine the interplay between the clouds, atmospheric circulations and climate sensitivity.

EUREC4A-UK will make a unique and self-contained contribution to the international programme by:

  1. providing observational facilities which are needed as part of the coordinated field campaign

  2. conducting and leading the analysis of the aerosols, cloud microphysics and boundary-layer processes in the life cycle of shallow trade cumulus clouds

  3. placing the analysis in the context of the EUREC4A problems by modelling the two-way interactions between the cloud processes and the large-scale dynamics

  4. applying the results by testing the new convection scheme in the UM and using the improved model to determine the dominant processes controlling the cloud fields

International partners will complement the research with a focus on observing and modelling the macrophysical properties and the environment of trade-cumulus clouds in order to determine:

  1. what controls the convective mass flux, mesoscale organization and depth of shallow-cumulus clouds

  2. how the trade-cumulus cloud fraction varies with turbulence, convective mixing and large-scale circulations

  3. the impact this variation has on atmospheric radiation

The radiative properties of the trade-wind cumulus clouds that are ubiquitous over the tropical oceans have a major influence on the Earth's radiation budget. The response to global warming of these clouds is therefore critical for global mean cloud feedbacks. It is the differing response to warming that explains most of the spread of climate sensitivity in climate models. Hence, a better understanding is required of the mechanisms that control the low-level cloud fraction. The urgency of the research is made clear by the fact that the World Climate Research Programme endorses the EUREC4A field project which supports the Grand Challenge on Clouds, Circulation and Climate Sensitivity.