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Title: Idealised and regional modelling study on cyclones' sensitivity to temperature
Author: Phibbs, Samuel Anthony
ISNI:       0000 0004 7228 7979
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Idealised tropical and extratropical cyclones, and a historic medicane are simulated using the Coupled-Ocean-Atmosphere-Wave-Sediment Transport Modeling System. This manuscript examines the sensitivity of: surface wind and waves to ocean temperature for tropical cyclones (TCs); precipitation to atmospheric temperature for extra-tropical cyclones; wind, waves and precipitation to simultaneous increases in atmospheric and oceanic temperature for the medicane. More intense and larger TCs, with higher waves, form when ocean temperature is increased. The maximum significant wave height increases more than the maximum wind speed for TCs up to hurricane-force wind. Above hurricane-force wind this relationship is reversed. This is explained by the wind drag coefficient dependence on wind speed. The relative increase in the footprint of high waves is considerably greater than the increase in the maximum wave height as ocean temperature is increased. This suggests a future warmer ocean will result in a large increase in the surface area of damaging waves generated by TCs. For the extratropical cyclones the footprint of extreme precipitation (total surface area where accumulated precipitation exceeds high thresholds) and the accumulation in different sized catchment areas is examined. The footprint of extreme precipitation grows considerably with temperature. When the catchment areas are ranked in order of total precipitation, super Clausius-Clapeyron behaviour of the 99th percentile is found for all the catchment sizes. This surprising result for larger catchment areas is due to spatially concentrated changes in the extreme precipitation. A more intense, significantly larger medicane generally developed when temperatures were increased. The greater area of high winds led to increases in both the maximum significant wave height and the footprint of high waves. The mean and extreme precipitation increased with temperature slightly and substantial faster than Clausius-Clapeyron scaling respectively, this was accompanied by a larger but less fragmented footprint of extreme precipitation.
Supervisor: Toumi, Ralf Sponsor: Natural Environmental Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral