Intra-seasonal differences in summer blocking patterns over Greenland

Summer Greenland blocking, a persistent anticyclonic pattern, has high impacts on local and regional weather and climate, especially on triggering huge melt over the Greenland ice sheet. The phenomenon is observed to increase in intensity (based on Greenland blocking index, GB2) in recent decades. This increase is highly correlated with the negative phase of the dominant climate oscillation in the North Atlantic, namely the NAO. However, summer NAO shows different behavior in June in comparison with high summer months, i.e., July and August. In this study, we analyse the spatial patterns of Greenland blocking events in these individual months to evaluate how different they are. We use different approaches including a clustering analysis with Self-Organising Map (SOM) to evaluate individual blocking days, and an event-based analysis to assess the development of blocking events over the course of 9 days centred at the day when GB2 reach maximum value during that event. The results from both analyses show that Greenland blocking patterns are more alike between July and August, while those of June are different.