Greenland’s Topography Triggers Cyclogenesis: Synergy between Lee Cyclogenesis and Jet Streak

Abstract. Arctic cyclones play a crucial role in shaping Arctic weather patterns and influencing sea ice concentrations. Notably, lee cyclogenesis—typically associated with large topographic barriers—has not been observed on the lee side of Greenland, despite its dominance as the Arctic’s largest terrain feature. During the MOSAiC expedition in April 2020, an Arctic cyclone was observed at the leeside of Greenland, prompting our hypothesis that lee cyclogenesis contributed significantly to its development.

To test this hypothesis, we conducted simulations with modified Greenland topography. The results confirm that lee cyclogenesis does occur and significantly enhances cyclone intensity. Notably, even when lee cyclogenesis is absent, the jet streak alone sustains cyclone development, suggesting that in this case, both mechanisms—lee cyclogenesis and the jet streak—collectively drive cyclogenesis.

Further analysis reveals the quasi-barotropic nature of lee cyclogenesis. Once the cyclone moves away from Greenland, lee cyclogenesis weakens markedly in the lower troposphere. However, the upper-tropospheric low vortex—induced by orographic forcing—persists, sustaining the cyclone until its dissipation in the central Arctic four days later. This suggests that orographic forcing has a prolonged impact in the upper troposphere. Our findings provide new insights into the mechanisms governing polar cyclone development.