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Precipitation is a key climate variable with large impact on society, but also difficult to simulate as it depends largely on temporal and spatial scales. We look here on the effect of model resolution on precipitation in Europe, from coarse scale global model to small scale regional models. Higher resolution improves simulated precipitation generally, bu individual models may over- or underestimate precipitation even at higher resolution.

Using a simple general circulation model, we examine the structure of waves in the mid-tropospheric jet over North Africa. We show that waves occur in near-stationary groups or wavepackets. As they are not swept out of the jet, this may provide the opportunity for the packets to amplify via feedback from other energy sources like rain-producing cloud complexes and mineral dust that are known to operate here. Our results address the criticism that the easterly jet is too short to sustain waves.

Observations of the stratosphere span roughly half a century preventing analysis of multi-decadal variability in circulation using these data. Instead, we rely on long simulations of climate models. Here, we use a model to examine variations in northern polar stratospheric winds and find they vary with a period of around 90 years. We show that this is possibly due to variations in the size of winds over the equator. This result may improve understanding of equator-polar stratospheric coupling.