EUCLIPSE First Period Report

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Figure 5. Schematic of the physical mechanism explaining the positive low-cloud feedback of
the IPSL-CM5A-LR ESM in climate change. The key role of changes in the vertical deficit of the
atmospheric moist static energy (shown on the right of the figure) in the energy budget of the
planetary boundary layer and the low-level cloudiness is highlighted. After Brient and Bony
(2011).
WP2 Conclusions, link to other WPs, and future plans :
As illustrated by this short report, WP2 activities are well on track. EUCLIPSE
participants have started to work on the different tasks of WP2, and progress is
expected on a number of issues:
- the evaluation of cloud processes in EUCLIPSE models
- the understanding of the influence of cloud processes on the tropical atmospheric
circulation and natural variability, and in European heat waves.
- the physical understanding of low-cloud feedbacks in EUCLIPSE models
- the development of new and original approaches to interpret inter-model differences
in cloud feedbacks and precipitation responses in climate change (these approaches
are currently being applied to CMIP5 models)
Most of the work done in WP2 is based on coordinated numerical experiments and
output diagnostics prepared in WP1 (global simulations from ESMs, OAGCM,
atmospheric and aqua-planet models; COSP outputs; high-frequency model outputs
over an ensemble of selected sites) and in WP3 (CGILS uni-column simulations, which
turn out to be very helpful to understand 3D cloud feedbacks). Thanks to the analysis
work carried out so far in WP2, several physical mechanisms have been identified as
playing a key role in the control of low-cloud feedbacks. In WP3 it will be possible to
assess these processes, and in WP4 it will be possible to design specific numerical
experiments to assess the actual role of these processes in cloud feedbacks
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