The Dynamical Tropopause Location as a Predictor for North Atlantic Tropical Cyclone Activity
Tropical cyclones are violent weather systems that can cause great damage to coastlines. Their successful prediction, on timescales ranging from a few days to the climate scale, has thus been a subject of scientific research for several decades. For the North Atlantic basin, seasonal and subseasonal...
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| Other Authors: | , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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ETH Zurich
2023
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| Subjects: | |
| Online Access: | https://hdl.handle.net/20.500.11850/642452 https://doi.org/10.3929/ethz-b-000642452 |
| Summary: | Tropical cyclones are violent weather systems that can cause great damage to coastlines. Their successful prediction, on timescales ranging from a few days to the climate scale, has thus been a subject of scientific research for several decades. For the North Atlantic basin, seasonal and subseasonal forecasts are operationally produced by various agencies to aid in estimating the potential for damage caused throughout the season. The 2013 hurricane season was predicted to be above average in activity. In reality, only two category 1 hurricanes, and no major hurricane, occurred, which is far below average. Predictions of the total number of tropical cyclones were generally correct, which suggests that the intensification of tropical cyclones was impeded. It has since been argued that an abundance of Rossby wave breaking events in the North Atlantic basin caused an increase in vertical wind shear and a reduction in mid-tropospheric humidity, which would militate against intensification. Rossby wave breaking event frequency, along with other related metrics, has therefore been proposed as a predictor for tropical cyclone activity. This thesis explores the latitudinal position of the tropopause in the western North Atlantic region, which is intrinsically linked to Rossby wave breaking events, as a simplified and more powerful predictor for tropical cyclone activity. The implementation of the tropopause latitude in predictions requires the use of numerical models. To assess whether the relation between the tropopause latitude and tropical cyclone activity is represented properly, tropical cyclones must be tracked. A tracking algorithm was thus developed for use with the ICON model. The tracking algorithm uses varying parameter thresholds to detect weaker systems and the comparatively weak tail ends of tropical cyclone tracks. It is shown that the algorithm can detect tropical cyclones during their formation stage, and can terminate them as they dissipate or transition into extratropical systems. False positives and ... |
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