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Title: Dynamically simulated tropical storms : their natural variability and response to climate change
Author: Bell, Ray
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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Tropical cyclones can cause substantial loss of life and an improved understanding of storm variability and their response to climate change can help inform preparation and future adaptation. The influence of the El Nino Southern Oscillation (ENSO) on global tropical cyclone activity is investigated in a high-resolution coupled climate model (Hi GEM) compared to an atmosphere-only simulation using the atmospheric component of Hi GEM (Hi GAM). HiGEM is able to capture the shift in tropical cyclone locations to ENSO in the Pacific and Indian Oceans but not in the North Atlantic. The vertical wind shear response over the Caribbean is not captured in HiGEM compared to HiGAM and ERA-Interim. Precipitation biases in HiGEM remain in HiGAM over the Western North Pacific, however HiGAM simulates a more accurate representation of the ENSO-tropical cyclone teleconnection. Model experiments are subsequently undertaken to investigate a contemporary issue on how different types ofEl Nino influence tropical cyclone activity in the Western North Pacific. The Hi GEM-Hi GAM central Pacific El Nino experiment simulates an increase of tropical cyclones that move towards South East Asia. This response is attributed to a large-scale anti-cyclonic anomaly over east China. In contrast, the low SST in the West Pacific during east Pacific El Nino reduces tropical cyclone activity. How tropical cyclone activity might change due to the influence of increased atmospheric carbon dioxide concentrations using HiGEM is finally investigated. Tropical cyclones are shown to decrease in frequency globally by 9 % in the 2XC02 (2C02) simulation and 26 % in the 4 x C02 (4C02) simulation. Tropical cyclones only become more intense in the 4C02. A decrease in mean ascent at 500 hPa contributes to the reduction of tropical cyclones in the 2C02 in most basins. The larger reduction of tropical cyclones in the 4C02 arises from further reduction of mean ascent at 500 hPa and a large enhancement of vertical wind shear.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available