Preprints
https://doi.org/10.5194/egusphere-2024-1876
https://doi.org/10.5194/egusphere-2024-1876
17 Jul 2024
 | 17 Jul 2024

DiuSST: A conceptual model of diurnal warm layers for idealized atmospheric simulations with interactive SST

Reyk Börner, Jan O. Haerter, and Romain Fiévet

Abstract. The diurnal variability of sea surface temperature (SST) may play an important role for cloud organization above the tropical ocean, with implications for precipitation extremes, storminess, and climate sensitivity. Recent cloud-resolving simulations demonstrate how imposed diurnal SST oscillations can strongly, and delicately, impact mesoscale convective organization. In spite of this nuanced interaction, many idealized modeling studies of tropical convection either assume a constant, homogeneous SST or, in case of a responsive sea surface, represent the upper ocean by a slab with fixed thickness. Here we show that slab ocean models with constant heat capacity fail to capture the wind-dependence of observed diurnal sea surface warming. To alleviate this shortcoming, we present a simple, yet explicitly depth-resolved model of upper-ocean temperature dynamics under atmospheric forcing. Our modular scheme describes turbulent mixing as diffusion with a wind-dependent diffusivity, in addition to a bulk mixing term and heat fluxes entering as sources and sinks. Using observational data, we apply Bayesian inference to calibrate the model. In contrast with a slab model, our model captures the exponential reduction of the diurnal warming amplitude with increasing wind speed. Further, our model performs comparably to a more elaborately parameterized diurnal warm layer model. Formulated as a single partial differential equation with three key tuning parameters, the model is suitable as an interactive numerical boundary condition for idealized atmospheric simulations.

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Journal article(s) based on this preprint

04 Mar 2025
DiuSST: a conceptual model of diurnal warm layers for idealized atmospheric simulations with interactive sea surface temperature
Reyk Börner, Jan O. Haerter, and Romain Fiévet
Geosci. Model Dev., 18, 1333–1356, https://doi.org/10.5194/gmd-18-1333-2025,https://doi.org/10.5194/gmd-18-1333-2025, 2025
Short summary
Reyk Börner, Jan O. Haerter, and Romain Fiévet

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2024-1876', Juan Antonio Añel, 14 Aug 2024
    • AC1: 'Reply on CEC1', Reyk Börner, 23 Aug 2024
      • CEC2: 'Reply on AC1', Juan Antonio Añel, 23 Aug 2024
  • RC1: 'Comment on egusphere-2024-1876', Anonymous Referee #1, 03 Sep 2024
  • CC1: 'Comment on egusphere-2024-1876', Justin Small, 19 Sep 2024
  • RC2: 'Comment on egusphere-2024-1876', Justin Small, 04 Oct 2024
  • AC2: 'Final response on egusphere-2024-1876', Reyk Börner, 17 Oct 2024

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2024-1876', Juan Antonio Añel, 14 Aug 2024
    • AC1: 'Reply on CEC1', Reyk Börner, 23 Aug 2024
      • CEC2: 'Reply on AC1', Juan Antonio Añel, 23 Aug 2024
  • RC1: 'Comment on egusphere-2024-1876', Anonymous Referee #1, 03 Sep 2024
  • CC1: 'Comment on egusphere-2024-1876', Justin Small, 19 Sep 2024
  • RC2: 'Comment on egusphere-2024-1876', Justin Small, 04 Oct 2024
  • AC2: 'Final response on egusphere-2024-1876', Reyk Börner, 17 Oct 2024

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Reyk Börner on behalf of the Authors (25 Nov 2024)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (04 Dec 2024) by Yang Tian
RR by Anonymous Referee #1 (05 Dec 2024)
RR by Anonymous Referee #2 (06 Dec 2024)
ED: Publish subject to technical corrections (03 Jan 2025) by Yang Tian
AR by Reyk Börner on behalf of the Authors (06 Jan 2025)  Author's response   Manuscript 

Journal article(s) based on this preprint

04 Mar 2025
DiuSST: a conceptual model of diurnal warm layers for idealized atmospheric simulations with interactive sea surface temperature
Reyk Börner, Jan O. Haerter, and Romain Fiévet
Geosci. Model Dev., 18, 1333–1356, https://doi.org/10.5194/gmd-18-1333-2025,https://doi.org/10.5194/gmd-18-1333-2025, 2025
Short summary
Reyk Börner, Jan O. Haerter, and Romain Fiévet
Reyk Börner, Jan O. Haerter, and Romain Fiévet

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Short summary
The daily warming and cooling of sea surface temperature (SST) impacts cloud formation above the ocean and can modulate the clustering of thunderstorms, as relevant for rainfall extremes and hurricanes. However, the daily SST cycle is often poorly represented in idealized modeling studies of cloud organization. To address this, we present a simple, wind-responsive model of upper ocean temperature for use in atmospheric simulations. We evaluate the model against observations and other models.
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