Cyclones from Sentinel-2: three dimensional reconstruction and wind speed using near simultaneous acquisitions
Résumé
Tropical cyclones (TCs) are among the most powerful and destructive natural phenomena on Earth, with significant impacts on and human lives and economies. Characterized by intense winds, heavy rainfall, and storm surges, TCs can lead to catastrophic flooding, and infrastructural damage. The increasing frequency and severity of these events, as observed in recent decades, underscore the urgent need for comprehensive understanding and effective mitigation strategies. The significance of studying cyclones extends beyond immediate disaster response. TCs play a crucial role in the global climate system, influencing atmospheric circulation patterns, ocean heat distribution, and precipitation regimes. Their interactions with sea surface temperatures (SSTs) and ocean heat content are particularly pertinent in the context of anthropogenic climate change. As global temperatures rise, alterations in oceanic and atmospheric conditions are anticipated to affect the genesis, intensity, and trajectories of TCs, potentially leading to more frequent rapid intensification events (RIEs) and higher peak wind speeds (Vv.Aa in Elsenr and Jagger, 2008; Holland and Bruyère, 2014 ). In this context, developing accurate methods for measurements of cyclones behavior is thus imperative for enhancing models via data assimilations. Advanced observational technologies, such as satellite platforms like the Copernicus Sentinel-2, can be used for cyclone monitoring by providing high spatial resolution (in contrast to low temporal resolution) data on atmospheric parameters such as the heights and the wind speeds of a tropical cyclone. In this study, we propose to use the near simultaneous acquisitions of Sentinel 2 to retrieve the three-dimensional height map of a cyclone as well as its wind speeds map at high spatial resolution. We developed a method that use interband-band image correlation as proposed in the past, with applications to volcanic clouds (e.g. de Michele et al. 2016). In this new approach, we can assume cylindrical symmetry for cloud heights and central symmetry (with respect to the TC center) for the velocity field. On this basis, we propose an approach for extracting heights and velocities of the upper surface of a TC from a Sentinel-2 dataset. Some critical technical points arise –to which we propose a solution- since the inverse problem is underdetermined/ill posed. We test our method to tropical cyclone Beryl, a Category 5 hurricane that impacted parts of the Caribbean, the Yucatán Peninsula and the Gulf Coast of the United States in late June and early July 2024. The first results show that the average error of the method (the absolute values of the differences between simulated and restored values) is 306m for heights and 4.1 m/s for velocities. Our conclusion is that the method could be used to investigate the interplay between cyclones vertical structure, and wind speed dynamics. This work highlights the role of satellite technologies like the Copernicus Sentinel-2 as a new tool for cyclone research.
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