Recent poleward shift of tropical cyclone genesis locations linked to tropical expansion (#15)
Recent research indicates that the observed annual-mean locations where tropical cyclones reach their lifetime-maximum intensity have migrated poleward in most ocean basins in recent decades. Concurrently an independent but anthropogenically-forced expansion of the tropical belt has been observed since 1980s. However, the possible connection between these two processes remains little-explored. Based on observational and reanalysis data, the present study investigates how large-scale dynamical effects, combined with coherent changes in the regional Hadley circulation, explain recent changes in regional tropical cyclone genesis for the period 1980–2014. We show that the recent anomalous upper-level weakening of the rising branch of the Hadley circulation in the deep tropics, possibly induced by the increased vertical stability, has likely suppressed the low-latitude tropical cyclone genesis in most ocean basins via anomalous large-scale subsidence. Regional Hadley circulation variations have also favoured a poleward displacement of tropical-cyclone-favourable climate conditions through poleward shift of the Hadley circulation’s meridional extent. With projections indicating continued tropical expansion, these results indicate that tropical cyclone genesis will also continue to shift poleward, potentially increasing tropical-cyclone-related hazards in higher-latitude regions.
- Sharmila S, and Walsh K (2018) Recent poleward shift of tropical cyclone formation linked to Hadley cell expansion. Nature Climate Change, DOI: https://doi.org/10.1038/s41558-018-0227-5.