The Annual Cycle of Climate Change over the North Atlantic

Relatively little attention has been paid to how the climate has varied throughout the annual cycle. In particular, there is a tendency to focus attention on the winter months, which are dynamically the most active. However, "climate noise" associated with weather variations is also larger during winter. Indeed, strong climate anomalies can be detected during other times of the year and, because the noise of natural variability is less, useful insights into the mechanisms responsible for those signals can be obtained. An examination of changes in the North Atlantic climate throughout the annual cycle will be presented, with an emphasis on summer.

In recent decades there has been a significant change in the climate over the North Atlantic and northern Europe during summer. Higher-than-average surface pressure, related to an increased tendency to blocking over the region, has led to significantly drier conditions and more frequent episodes of drought. A diagnosis of the primary physical and dynamical processes associated with this interdecadal climate signal will be presented.