Assessing South Indian Ocean tropical cyclone characteristics in HighResMIP simulations

Pardeep Pall*, Alexandre S. Gagnon, Massimo Bollasina, Colin Zarzycki, Yuner Huang, Christopher T. S. Beckett, Harinaivo Ramanantoanina, Thomas Reynolds

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Several damaging tropical cyclones (TCs) have occurred recently over the South Indian Ocean (SIO) region, causing enormous social and economic losses. Yet, while many studies have examined SIO TC characteristics using observations and reanalysis, only a few have assessed these characteristics specifically for this region in climate models, and fewer have investigated their projections under climate change. Here we do this for a historical (1980-2010) and future (2020-2050) period, using multi-model simulations from the High Resolution Model Intercomparison Project, as well as examine biases in the historical period relative to a reanalysis (ERA5). The models have horizontal resolutions of 25-50 km, which has enabled an improved ability to represent tropical cyclones globally in previous studies. TempestExtremes software is employed to detect tropical storm and cyclone tracks. In cases where TempestExtremes cannot be applied due to a lack of requisite variables in a dataset, we instead examine extreme wind speeds in that dataset. For the historical period, we find considerable variation in model biases compared to ERA5, which itself exhibits realistic spatial patterns of tracks and their monthly distribution. Models do at least agree on positive biases in track frequency east of Madagascar and somewhat in the Mozambique Channel. However, the models and ERA5 only produce category 3 tropical cyclones at best. Wind speeds for 25km resolution models have much larger positive biases than for 50km ones, suggesting the former can simulate even higher-category tropical cyclones. Considerable inter-model variation is also found in track changes between the future and historical periods. No systematic inter-category pattern of change exists, and low signal-to-noise may obscure any such patterns in the limited timespan of available data. Thus, no meaningful conclusions can be drawn regarding changes in track intensity. Nevertheless, track frequency broadly decreases across models for the region, as does accumulated cyclone energy. An east-to-west shift in track location from east of Madagascar toward the Mozambique Channel is also implied by track frequency and wind speed changes. Our findings provide information to potentially improve storm resiliency in this vulnerable region.
Original languageEnglish
JournalInternational Journal of Climatology
Early online date11 Sept 2024
DOIs
Publication statusE-pub ahead of print - 11 Sept 2024

Keywords / Materials (for Non-textual outputs)

  • ERA5
  • HighResMIP
  • South Indian Ocean
  • tropical cyclones

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