Preprints
https://doi.org/10.5194/gmd-2022-7
https://doi.org/10.5194/gmd-2022-7
Submitted as: model description paper
27 Jan 2022
Submitted as: model description paper | 27 Jan 2022
Status: a revised version of this preprint was accepted for the journal GMD and is expected to appear here in due course.

The Regional Coupled Suite (RCS-IND1): application of a flexible regional coupled modelling framework to the Indian region at km-scale

Juan Manuel Castillo1, Huw Lewis1, Akhilesh Mishra2, Ashis Mitra2, Jeff Polton3, Ashley Brereton3, Andrew Saulter1, Alex Arnold1, Segolene Berthou1, Douglas Clark4, Julia Crook5, Ananda Das6, John Edwards1, Xiangbo Feng7, Ankur Gupta2, Sudheer Joseph8, Nicholas Klingaman7, Imranali Momin2, Christine Pequignet1, Claudio Sanchez1, Jennifer Saxby5, and Maria Valdivieso da Costa7 Juan Manuel Castillo et al.
  • 1Met Office, Exeter, EX1 3PB, UK
  • 2National Centre for Medium Range Weather Forecasting (NCMRWF), India
  • 3National Oceanography Centre, Liverpool, UK
  • 4UK Centre of Ecology & Hydrology (UKCEH), UK
  • 5University of Leeds, UK
  • 6India Meteorological Department (IMD), India
  • 7University of Reading, UK
  • 8INCOIS, India

Abstract. A new regional coupled modelling framework is introduced – the Regional Coupled Suite (RCS). This provides a flexible research capability with which to study the interactions between atmosphere, land, ocean and wave processes resolved at km-scale, and the effect of environmental feedbacks on the evolution and impacts of multi-hazard weather events. A configuration of the RCS focussed on the Indian region, termed RCS-IND1, is introduced. RCS-IND1 includes a regional configuration of the Unified Model (UM) atmosphere, directly coupled to the JULES land surface model, on a grid with horizontal spacing of 4.4 km, enabling convection to be explicitly simulated. These are coupled through OASIS3-MCT libraries to 2.2 km grid NEMO ocean and WAVEWATCH III wave model configurations. To examine a potential approach to reduce computation cost, and simplify ocean initialisation, the RCS includes an alternative approach to couple the atmosphere to a lower resolution Multi-Column K Profile Parameterization (KPP) for the ocean. Through development of a flexible modelling framework, a variety of fully and partially coupled experiments can be defined, along with traceable uncoupled simulations and options to use external input forcing in place of missing coupled components. This offers a wide scope to researchers designing sensitivity and case study assessments. Case study results are presented and assessed to demonstrate the application of RCS-IND1 to simulate two tropical cyclone cases which developed in the Bay of Bengal, namely Titli in October 2018 and Fani in April 2019. Results show realistic cyclone simulations, and that coupling can improve the cyclone track and produces more realistic intensification than uncoupled simulations for Titli but prevents sufficient intensification for Fani. Atmosphere-only UM regional simulations omit the influence of frictional heating on the boundary layer to prevent cyclone over-intensification. However, it is shown that this term can improve coupled simulations, enabling a more rigorous treatment of the near-surface energy budget to be represented. For these cases, a 1D mixed layer scheme shows similar first-order SST cooling and feedback on the cyclones as a 3D ocean. Nevertheless, the 3D ocean generally shows stronger localised cooling than the 1D ocean. Coupling with the waves have limited feedback on the atmosphere for these cases. Priorities for future model development are discussed.

Juan Manuel Castillo et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2022-7', Anonymous Referee #1, 06 Feb 2022
    • RC3: 'Reply on RC1', Anonymous Referee #3, 21 Feb 2022
  • RC2: 'Comment on gmd-2022-7', Anonymous Referee #2, 18 Feb 2022
  • AC1: 'Comment on gmd-2022-7', Huw Lewis, 22 Apr 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2022-7', Anonymous Referee #1, 06 Feb 2022
    • RC3: 'Reply on RC1', Anonymous Referee #3, 21 Feb 2022
  • RC2: 'Comment on gmd-2022-7', Anonymous Referee #2, 18 Feb 2022
  • AC1: 'Comment on gmd-2022-7', Huw Lewis, 22 Apr 2022

Juan Manuel Castillo et al.

Data sets

Data used in preparation of manuscript figures Castillo, J. M. et al. https://doi.org/10.5281/zenodo.5831574

Juan Manuel Castillo et al.

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Short summary
A new environmental modelling system has been developed to represent the effect of feedbacks between atmosphere, land and ocean in the Indian region. Different approaches to simulating tropical cyclones Titli and Fani are demonstrated. It is shown that results are sensitive to the way in which the ocean response to cyclone evolution is captured in the system. Notably, we show how a more rigorous formulation for the near-surface energy budget can be included when air-sea coupling is included.