Dec 13, 2017

Attribution of extreme rainfall from Hurricane Harvey, August 2017

by
Geert Jan van Oldenborgh, Karin van der Wiel, Antonia Sebastian, Roop Singh, Julie Arrighi, Friederike Otto, Karsten Haustein, Sihan Li, Gabriel Vecchi and Heidi Cullen
,
World Weather Attribution, Environmental Research Letters
  • States that during August 25–30, 2017, Hurricane Harvey stalled over Texas and caused extreme precipitation, particularly over Houston and the surrounding area on August 26–28, causing extensive flooding with over 80 fatalities and large economic costs
  • Conducts an observational analysis, primarily using two rain gauge-based datasets
  • Analyzes extreme rainfall in the Houston area in three ensembles of 25 km resolution models
  • Finds that the three-day rainfall sums that were responsible for most of the flooding were extremely rare, with a return time for station observations of more than 9000 years in the current climate
  • Finds that observations since 1880 over the region show a clear positive trend in the intensity of extreme precipitation of between 12% and 22%, roughly two times the increase of the moisture holding capacity of the atmosphere expected for 1 °C warming according to the Clausius–Clapeyron (CC) relation
  • Extrapolates these results to the 2017 event, concluding that global warming made the precipitation about 15% (8%–19%) more intense, or equivalently made such an event three (1.5–5) times more likely