EGU21-8360
https://doi.org/10.5194/egusphere-egu21-8360
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Strongly Coupled Assimilation of a Hypothetical Ocean Current Observing Network within a Regional Ocean-Atmosphere Coupled Model: An OSSE Case Study of Typhoon Hato

Luke Phillipson1, Yi Li2, and Ralf Toumi1
Luke Phillipson et al.
  • 1Imperial College London, Faculty of Natural Sciences , Department of Physics, United Kingdom of Great Britain – England, Scotland, Wales (l.phillipson14@imperial.ac.uk)
  • 2College of Oceanography, Hohai University, Nanjing, China

The forecast of tropical cyclone (TC) intensity is a significant challenge.  In this study, we showcase the impact of strongly coupled data assimilation with hypothetical ocean currents on analyses and forecasts of Typhoon Hato (2017). 

Several observation simulation system experiments were undertaken with a regional coupled ocean-atmosphere model. We assimilated combinations of (or individually) a hypothetical coastal current HF radar network, a dense array of drifter floats and minimum sea-level pressure. During the assimilation, instant updates of many important atmospheric variables (winds and pressure) are achieved from the assimilation of ocean current observations using the cross-domain error covariance, significantly improving the track and intensity analysis of Typhoon Hato. As compared to a control experiment (with no assimilation), the error of minimum pressure decreased by up to 13 hPa (4 hPa / 57 % on average). The maximum wind speed error decreased by up to 18 knots (5 knots / 41 % on average). 

By contrast, weakly coupled implementations cannot match these reductions (10% on average). Although traditional atmospheric observations were not assimilated, such improvements indicate there is considerable potential in assimilating ocean currents from coastal HF radar, and surface drifters within a strongly coupled framework for intense landfalling TCs.

How to cite: Phillipson, L., Li, Y., and Toumi, R.: Strongly Coupled Assimilation of a Hypothetical Ocean Current Observing Network within a Regional Ocean-Atmosphere Coupled Model: An OSSE Case Study of Typhoon Hato, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8360, https://doi.org/10.5194/egusphere-egu21-8360, 2021.

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