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Orographic effect on extreme precipitation statistics peaks at hourly time scales
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  • Francesco Marra,
  • Moshe Armon,
  • Marco Borga,
  • Efrat Morin
Francesco Marra
Institute of Atmospheric Sciences and Climate, National Research Council

Corresponding Author:[email protected]

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Moshe Armon
Institute of Earth Sciences, Hebrew University of Jerusalem
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Marco Borga
University of Padova
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Efrat Morin
Institute of Earth Sciences, The Hebrew University of Jerusalem
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Orographic impact on extreme sub-daily precipitation is critical for risk management but remains insufficiently understood due to complicated atmosphere-orography interactions and large uncertainties. We investigate the problem adopting a framework able to reduce uncertainties and isolate the systematic interaction of Mediterranean cyclones with a regular orographic barrier. The average decrease with elevation reported for hourly extremes is found enhanced at sub-hourly durations. Tail heaviness of 10-minute intensities is negligibly affected by orography, suggesting self-similarity of the distributions at the convective scale. Orography decreases the tail heaviness at longer durations, with a maximum impact around hourly scales. These observations are explained by an orographically-induced redistribution of precipitation towards stratiform-like processes, and by the succession of convective cores in multi-hour extremes. Our results imply a breaking of scale-invariance at sub-hourly durations, with important implications for natural hazards management in mountainous areas.
16 Mar 2021Published in Geophysical Research Letters volume 48 issue 5. 10.1029/2020GL091498