Climate factor clouds – the field campaign EUREC4A intends to answer one of climate science’s great mysteries
A field study including meteorologists from the University of Cologne will explore the effect of clouds on earth’s climate / research aircrafts and vessels, observatories and climate models will provide new data
On 20 January 2020, the almost six-week field study EUREC4A (Elucidating the role of clouds-circulation coupling in climate) will start. It aims at validating theories on the role of clouds and convection for climate change through extensive measurements in the atmosphere and ocean. The French-German initiated field study involves more than 40 partner institutions and the deployment of five research aircrafts, four research vessels, ground based remote sensing and satellite remote sensing east and south of the Caribbean island of Barbados. EUREC4A is led by Prof Bjorn Stevens, Director of the Max Planck Institute for Meteorology (MPI-M) in Hamburg, and Dr Sandrine Bony, Director of Research at the Laboratoire de Météorologie Dynamique in Paris. Their initiative builds on, and extends, a decade of cooperation with Barbadian scientists at the Caribbean Institute for Meteorology and Hydrology (CIMH), under the leadership of its Principal, Dr David Farrell.
Clouds are an essential climate factor. How shallow clouds in the trade wind regions react to global warming determines to a large extent how fast and intensive future climate change will be. Science has so far investigated the role of clouds and convection in the climate system using theories and climate models. To verify these, researchers need observational data on the dynamics of the atmospheric and oceanic conditions in which the clouds form and dissolve. With the extensive measurements during the EUREC4A field study, they will study the life cycle of convective clouds in the trade wind region in great detail in order to obtain as complete a picture as possible.
Analyses of the international climate model intercomparison studies (CMIP) over the last decades have shown that a reduction in the trade wind clouds caused by global warming leads to a further increase in global warming, a so-called positive feedback. Principal investigator Bjorn Stevens: ‘We will test whether the behavior of models, which show a large decrease in cloud cover with warming, is correct. If so, it would imply that higher estimates of the expected warming from increasing CO2 are more plausible. For the question of the cloud response to climate change there is still much uncertainty. We intend for EUREC4A to change that.’
In numerical models, trade wind cumuli react differently to climate perturbations. Complex climate models project that the area covered by shallow clouds is very sensitive to the surrounding environment while process models show the opposite. Understanding and resolving these contradictions are the basis for the field study EUREC4A.
Principal investigator Sandrine Bony: ‘Estimates of climate sensitivity remain very uncertain, and most of this uncertainty stems from the response of low-level clouds in the tropics, especially in the trade-wind regions. The low-clouds near Barbados are representative of the low-clouds that populate the trade-wind regions over the whole Tropics. Hence, what we will learn from EUREC4A will not only serve our understanding of Barbados clouds but of tropical clouds more generally.’
The nucleus for the field study involves the deployment of five research aircrafts, four ocean-going research vessels, advanced ground based remote sensing at MPI-M’s Barbados Cloud Observatory (BCO), a new generation of sophisticated satellite remote sensing methods, and state-of-the-art turbulence-resolving climate models. Susanne Crewell, University of Cologne, explains the special features of the campaign structure: ‘Only through this combination of diverse measurements and high-resolution simulations is it possible to analyse the decisive processes in detail and thus expand our understanding.’
From Germany, four Max Planck Institutes are involved in the campaign (MPI-M, MPI for Dynamics and Self-Organization, MPI for Chemistry and MPI for Marine Microbiology), five universities (Cologne, Hamburg, Hohenheim, Leipzig and Munich), three Helmholtz institutions (DLR, GEOMAR and HZG), the Leibniz Institute TROPOS and the German Meteorological Service (DWD).
EUREC4A is funded by: European Research Council (ERC), Max Planck Society (MPG), Centre National de Recherche Scientific (CNRS), German Research Foundation (DFG, Deutsche Forschungsgemeinschaft), Caribbean Institute for Meteorology and Hydrology (CIMH), Natural Environment Research Council (NERC), and World Climate Research Programme (WCRP).