Preprints
https://doi.org/10.5194/wcd-2021-46
https://doi.org/10.5194/wcd-2021-46

  26 Jul 2021

26 Jul 2021

Review status: this preprint is currently under review for the journal WCD.

Simulations of Bay of Bengal tropical cyclones in a regional convection-permitting atmosphere–ocean coupled model

Jennifer Saxby1, Julia Crook1, Simon Peatman1, Cathryn Birch1, Juliane Schwendike1, Maria Valdivieso da Costa2, Juan Manuel Castillo Sanchez3, Chris Holloway2, Nicholas P. Klingaman2, Ashis Mitra4, and Huw Lewis3 Jennifer Saxby et al.
  • 1School of Earth and Environment, University of Leeds, UK
  • 2National Centre for Atmospheric Science and Department of Meteorology, University of Reading, UK
  • 3Met Office, UK
  • 4National Centre for Medium Range Weather Forecasting, India

Abstract. Tropical cyclones (TCs) in the Bay of Bengal can be extremely destructive when they make landfall in India and Bangladesh. Accurate prediction of their track and intensity is essential for disaster management. This study evaluates simulations of Bay of Bengal TCs using a regional convection-permitting atmosphere-ocean coupled model. The Met Office Unified Model atmosphere-only configuration (4.4 km horizontal grid spacing) is compared with a configuration coupled to a three-dimensional dynamical ocean model (2.2 km horizontal grid spacing). Simulations of six TCs from 2016–2019 show that both configurations produce accurate TC tracks for lead times of up to 6 days before landfall. Both configurations underestimate high wind speeds and high rain rates, and overestimate low wind speeds and low rain rates. The ocean-coupled configuration improves landfall timing predictions and reduces wind speed biases relative to observations outside the eyewall but underestimates maximum wind speeds in the eyewall for the most intense TCs. The coupled configuration produces weaker TCs than the atmosphere-only configuration, consistent with lower sea surface temperatures in the coupled model and an overestimated cooling response in TC wakes. Both model configurations accurately predict rain rate asymmetry, suggesting a good representation of TC dynamics. Much of the rain rate asymmetry variation in the simulations is related to wind shear variations, with a preference for higher rain rates in the down-shear left quadrant.

Jennifer Saxby et al.

Status: open (until 18 Sep 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2021-46', Anonymous Referee #1, 18 Aug 2021 reply

Jennifer Saxby et al.

Jennifer Saxby et al.

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Short summary
This study assesses the ability of the new Met Office IND1 numerical model to simulate tropical cyclones and their associated hazards, such as high winds and heavy rainfall. The new system consists of both atmospheric and oceanic models coupled together, allowing us to explore the sensitivity of cyclones to important air–sea feedbacks. We find that the model can accurately simulate tropical cyclone position, structure, and intensity, which are crucial for predicting and mitigating hazards.