Zhang et al. (2025) Simulation and Analysis of Sea Surface Skin Temperature Diurnal Variation Using a One-Dimensional Mixed Layer Model and Himawari-8 Data

Identification

• Journal: Remote Sensing
• Year: 2025
• Date: 2025-12-23
• Authors: Xianliang Zhang, Pinyan Xu, Zexi Mao, Longwei Zhang, Xuan Sang, Z. P. Mao
• DOI: 10.3390/rs18010043

Research Groups

• Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China
• State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, China
• University of Chinese Academy of Sciences, Beijing, China
• School of Marine Science, University of Maine, Orono, ME, USA
• School of Oceanography, Shanghai Jiao Tong University, Shanghai, China

Short Summary

This study aimed to capture Sea Surface Skin Temperature (SSTskin) diurnal warming events and evaluate the performance of an improved one-dimensional mixed-layer model (PWP) in simulating SSTskin. The improved PWP model reproduced the diurnal variation cycle consistently with Himawari-8 observations, but showed abnormal overestimation in low-wind-speed areas due to rapid mixed-layer thinning and lack of horizontal diffusion.

Objective

• To capture Sea Surface Skin Temperature (SSTskin) diurnal warming events using high-frequency satellite observations.
• To evaluate the performance of an improved one-dimensional mixed-layer model (PWP) in simulating SSTskin and its diurnal variation.

Study Configuration

• Spatial Scale: Himawari-8 full-disk coverage (80°E to 160°W longitude, 60°N to 60°S latitude) with 2 km spatial resolution at nadir. Simulation area focused on the northwestern Australian coast (e.g., 120–125°E, 13–14°S) with 90 grid points at 0.25° × 0.25° resolution. The PWP model used an upper water layer thickness of 0.1 m and a simulated mixed layer depth of 150 m.
• Temporal Scale: Study period from 9 September 2020 to 13 September 2020, with a focus on 12 September 2020. Himawari-8 observations were at 10-minute intervals. The PWP model used a time step of 300 seconds (5 minutes). ERA5 reanalysis data provided hourly estimates.

Methodology and Data

• Models used:
  • Improved Price-Weller-Pinkel (PWP) one-dimensional mixed-layer model (PWP2.0 version).
  • SSTskin parameterization scheme by Zhang et al. [37].
  • Surface albedo model by Jin et al. [36].
• Data sources:
  • Satellite: Himawari-8 (Advanced Himawari Imager - AHI) SSTskin products (2 km spatial resolution, 10 min temporal resolution). MODIS-AQUA (for chlorophyll concentration).
  • In situ: iQuam (in situ SST Quality Monitor) drifter buoy SST data (quality flag = 5).
  • Reanalysis:
    • ERA5 (European Centre for Medium-Range Weather Forecasts) reanalysis dataset (0.25° resolution for fluxes, 0.125° for wind field) for net longwave radiation flux, net shortwave radiation flux, upward latent heat flux, upward sensible heat flux, precipitation, and wind speed.
    • GLORYS12V1 (Global Ocean Physics Reanalysis Dataset) for initial temperature, salinity, and sea surface current fields.

Main Results

• Himawari-8 SSTskin data validation against iQuam in situ observations showed a mean bias of -0.28 °C, a mean absolute bias of 0.48 °C, a root mean square error (RMSE) of 0.69 °C, a robust standard deviation (RSD) of 0.20 °C, and a correlation coefficient (R) of 1.00.
• A typical diurnal warming event was observed by Himawari-8 off the northwestern Australian coast on 12 September 2020, with the maximum SSTskin diurnal variation reaching 3 °C.
• The improved PWP model reproduced the diurnal variation cycle consistently with Himawari-8 observations, accurately matching regions with significant warming, and achieved a mean bias of -0.37 °C.
• In low-wind-speed areas (<1 m/s), the PWP model exhibited abnormal SSTskin overestimation (>3 °C), with the maximum overestimation nearly 3-fold compared to Himawari-8 observations.
• This overestimation in low-wind conditions is attributed to rapid thinning of the mixed layer and the absence of horizontal diffusion in the one-dimensional model.
• The difference between the 0.1 m seawater layer temperature and SSTskin was smaller during the warming phase of the diurnal warming event compared to the cooling phase, indicating a weaker cool skin effect during warming.

Contributions

• Demonstrated the capability of an improved one-dimensional mixed-layer model (PWP with SSTskin parameterization) to simulate SSTskin diurnal variations, providing a computationally efficient tool for studying upper-ocean vertical processes.
• Utilized high-frequency geostationary satellite observations (Himawari-8) for direct, spatially extensive validation of SSTskin diurnal cycles, which is less common in existing literature.
• Identified and quantified the limitations of the PWP model, specifically abnormal SSTskin overestimation under very low-wind-speed conditions (<1 m/s), attributing it to rapid mixed-layer thinning and the lack of horizontal diffusion.
• Provided a clear direction for future model optimization by highlighting the need to evaluate vertical mixing schemes in low-wind conditions and consider horizontal diffusion or fully coupled air-sea models to enhance SSTskin simulation accuracy.

Funding

• National Key Research and Development Program of China (Grant 2023YFC3107605)
• National Natural Science Foundation of China (Grant 61991454)
• Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (Grant SL2022ZD206)
• Scientific Research Fund of Second Institute of Oceanography, MNR (Grant SL2302)

Citation

@article{Zhang2025Simulation,
  author = {Zhang, Xianliang and Xu, Pinyan and Mao, Zexi and Mao, Zexi and Zhang, Longwei and Sang, Xuan and Mao, Z. P. and Mao, Z. P.},
  title = {Simulation and Analysis of Sea Surface Skin Temperature Diurnal Variation Using a One-Dimensional Mixed Layer Model and Himawari-8 Data},
  journal = {Remote Sensing},
  year = {2025},
  doi = {10.3390/rs18010043},
  url = {https://doi.org/10.3390/rs18010043}
}