Tracking tropical cyclone impacts using altimetry

By Ben Loveday, Rosmorduc Vinca (CLS), Hayley Evers-King and Carla Barroso 

Tropical cyclones have been responsible for more than 700,000 deaths and 1,400 billion US dollars worth of damage in the last 50 years (WMO). They are a major use case for meteorological satellite data, and a challenge for weather forecasting.

Beyond observation and prediction of tropical cyclones as an atmospheric phenomenon, there is also an ocean component to consider, both in terms of storm formation, and of their impacts.

Satellites provide measurements of sea surface temperature, which, along with altimetry measurements, can be used to estimate tropical cycle heat potential, a key factor in forecasting cyclones and their intensity. Altimetry data can also be used to measure the ocean response to tropical cyclones, and, ultimately, its impact on maritime activities and coastal communities through high winds, storm surges, and extreme wave heights.

Tropical cyclones also need to be monitored in the context of climate change, which has the potential to alter atmospheric circulations and ocean heat content, and exacerbate the impacts of cyclones through sea level rise. 

Tropical cyclones can be observed in both optical and infrared imagery from weather satellites. Figure 1, created using the EUMETView Web Map Service (WMS), shows multiple tropical cyclones observed in the Airmass RGB taken from several Meteosat and GOES satellites, in addition to Himawari-8. Together, these geostationary missions can provide global coverage showing storm formation and progression.

For an alternative look at two of these storms, please follow these EUMETView views of typhoons Hinnanmor and Nanmadol.

Figures 2a to 2d show examples of several typhoons and hurricanes in 2022. The track of the storm, extracted from the International Best Track Archive for Climate Stewardship (IBTrACS) record, is shown in rings. Ring size approximates the diameter of the storm (the outermost closed isobar). Ring colour indicating the intensity of the storm, reflected in the maximum wind intensity in km/h. The tracks show significant wave height record extracted from Sentinel-3 SRAL and Sentinel-6 passes that fall within +/- 6 hours of the displayed storm position. Sentinel-6 passes are highlighted in a thin grey line. These are overlaid on the multi-mission geostrophic ring convection product (shading) and GEBCO bathymetry, with contours (darkest to lightest) at 4000m, 3000m, 2000m, 1000m, 500m and 100m.

As well as providing valuable near-real time and long-term observations of ocean parameters relevant to storm formation and impacts, ocean satellite data is also assimilated into models.

Figures 3a to 3d show the corresponding wave fields for the cyclones, as extracted form the CMEMS global wave forecast model. Colour shows the total significant wave height (SWH), with the combined influence of wave and swell-induced components. Arrows show the direction the waves are travelling, with arrow size scaled by the SWH. No arrows are shown where SWH is less than 4m. This is overlaid on the GEBCO bathymetry, with contours (darkest to lightest) at 4000m, 3000m, 2000m, 1000m, 500m and 100m.

Relevance to ocean challenges, and further resources

As part of the United Nations Ocean Decade, ten specific challenges are being addressed. This work, and the data underlying it, support Challenge 6 - Increase community resilience to ocean hazards. Estimates of significant wave height and wind speed, derived from the sea surface topography missions, are an essential input into the forecasting systems that allow us to provide early warnings to coastal populations.

To support the UN Ocean Decade this case study has an accompanying Jupyter Notebook, which revisits the narrative and replicates some of the figures you see here. You can find this notebook in our ocean case studies repository, which you are free to clone for your own use or to support your own training. Alternatively, you can launch the notebook directly on Binder.

This case study is a contribution to the United Nations Ocean Decade