Orographic impacts of Réunion Island and Madagascar on heavy rainfall during Tropical Cyclone Batsirai (2022)
Abstract
During the passage of tropical cyclone (TC) Batsirai (2022), the mountainous regions of Réunion Island and the eastern part of Madagascar experienced devastating floods. TC Batsirai passed north of Réunion Island (minimum distance of ∼ 210 km) before making landfall along the eastern coast of Madagascar. Using a non-hydrostatic research atmospheric model at 2 km resolution, we conducted a control simulation with realistic topography (CTL) and three flattened-terrain experiments (FLTall, FLTmdg, and FLTreu) to assess orographic effects. Relative to the flattened-terrain experiments, the presence of terrain increased localized rainfall by 96 % (2906 mm) over Réunion Island (CTL versus FLTreu) and 82 % (830 mm) over Madagascar (CTL versus FLTall), respectively. Over Réunion Island, orographically uplifted low-level moisture sustained 60 h of heavy rainfall (10 mm h⁻¹), with a peak of 96 mm h⁻¹, although the cyclone's intensity and track were minimally affected. In Madagascar, terrain not only intensified precipitation (19 h of heavy rainfall with a peak intensity of 92.8 mm h⁻¹) but also altered the TC trajectory, delaying landfall by about 12 h and shifting it approximately 30 km south. These findings highlight the critical role of complex orography in shaping localized rainfall and TC behaviour in the southwest Indian Ocean.
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BibTeX
@article{lee2026orographic,
title = {{Orographic impacts of Réunion Island and Madagascar on heavy rainfall during Tropical Cyclone Batsirai (2022)}},
author = {Keun-Ok Lee and Soline Bielli and Clément Soufflet and Rémi Laxenaire and Kevin Hoarau},
journal = {Atmospheric Chemistry and Physics},
year = {2026},
month = sep,
doi = {10.5194/acp-26-12435-2026},
url = {https://hal.science/hal-05752706v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Orographic impacts of Réunion Island and Madagascar on heavy rainfall during Tropical Cyclone Batsirai (2022)
AU - Keun-Ok Lee
AU - Soline Bielli
AU - Clément Soufflet
AU - Rémi Laxenaire
AU - Kevin Hoarau
PY - 2026
DA - 2026/09/17
JO - Atmospheric Chemistry and Physics
DO - 10.5194/acp-26-12435-2026
UR - https://hal.science/hal-05752706v1
AB - During the passage of tropical cyclone (TC) Batsirai (2022), the mountainous regions of Réunion Island and the eastern part of Madagascar experienced devastating floods. TC Batsirai passed north of Réunion Island (minimum distance of ∼ 210 km) before making landfall along the eastern coast of Madagascar. Using a non-hydrostatic research atmospheric model at 2 km resolution, we conducted a control simulation with realistic topography (CTL) and three flattened-terrain experiments (FLTall, FLTmdg, and FLTreu) to assess orographic effects. Relative to the flattened-terrain experiments, the presence of terrain increased localized rainfall by 96 % (2906 mm) over Réunion Island (CTL versus FLTreu) and 82 % (830 mm) over Madagascar (CTL versus FLTall), respectively. Over Réunion Island, orographically uplifted low-level moisture sustained 60 h of heavy rainfall (10 mm h⁻¹), with a peak of 96 mm h⁻¹, although the cyclone's intensity and track were minimally affected. In Madagascar, terrain not only intensified precipitation (19 h of heavy rainfall with a peak intensity of 92.8 mm h⁻¹) but also altered the TC trajectory, delaying landfall by about 12 h and shifting it approximately 30 km south. These findings highlight the critical role of complex orography in shaping localized rainfall and TC behaviour in the southwest Indian Ocean.
SN - 1680-7316
SN - 1680-7324
ER -