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Projects in Research Area A – Upscale Error Growth

Local processes, such as cumulus convection or flow over orography, create disturbances in the atmospheric
flow, but most are unimportant for the future development of the weather. In order to have an influence over several days and many thousands of kilometers, the disturbances need to project onto the synoptic scale,
geostrophically balanced modes that dominate the midlatitude atmosphere. To understand and model this
chain of events requires progress in the physical problem of the mechanisms for upscale growth, the statistical
or stochastic problem of modeling the unpredictable, small-scale processes that trigger disturbance growth,
and the data analysis problem of how to represent the changing uncertainty represented by an ensemble of

Projects in Research Area B – Cloud-scale Uncertainties

Clouds are a major contributor to uncertainty in weather prediction for several reasons. They are composed
of microphysical particles that grow, dissipate and interact in complex processes. Cloud particles interact
with the atmospheric flow through release and absorption of latent heat, through precipitation, and through
radiative feedbacks and mixing. This can give rise to complex dynamical structure on scales as small as tens of meters, but also to impacts on growing weather systems such as convective clouds and synoptic cyclones. A
further source of complexity is that clouds are sensitive to environmental factors such as temperature, humidity,
transport and aerosol content. These different sources of uncertainty must be investigated in detail in order
to represent their effects accurately in weather prediction systems.

Projects in Research Area C – Predictability of local Weather

The prediction of a local weather event is affected by the synoptic-scale environment and by local processes and
instabilities. The uncertainty of a forecast will be determined by a combination of these factors. However, the
processes contributing to this uncertainty are as diverse as the weather systems themselves. An investigation
of the predictability of local weather must consider a wide variety of dynamical processes and weather events,
to achieve the final goal of a probabilistic forecast that is useful for society.

Central projects Z