ORIGINAL RESEARCH article

Front. Mar. Sci.

Sec. Ocean Observation

Volume 12 - 2025 | doi: 10.3389/fmars.2025.1587000

This article is part of the Research TopicRemote Sensing Applications in Marine Ecology Monitoring and Target SensingView all 10 articles

Investigating SST Diurnal Variation and its Response to the MJO in the North Indian Ocean Using FY-4A Data

Provisionally accepted
Xianliang  ZhangXianliang Zhang1,2,3Mao  ZhihuaMao Zhihua1,2*Longwei  ZhangLongwei Zhang2Xuan  SangXuan Sang2
  • 1Shanghai Institute of Technical Physics, Chinese Academy of Sciences (CAS), Shanghai, Shanghai Municipality, China
  • 2Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, Zhejiang Province, China
  • 3University of Chinese Academy of Sciences, Beijing, Beijing, China

The final, formatted version of the article will be published soon.

This study investigates sea surface temperature (SST) diurnal variation in the North Indian Ocean by employing hourly data from the FY-4A geostationary satellite, in conjunction with reanalysis products and the Madden-Julian Oscillation (MJO) index. Validation against in situ SST measurements shows a bias of -0.33°C, an absolute bias of 0.73°C, an RSD of 0.33°C, an RMSE of 0.94°C, and a correlation coefficient of 0.90. The results demonstrate consistent accuracy throughout the diurnal cycle. Diurnal warming is most pronounced in the northern Arabian Sea and northern Bay of Bengal, especially from March to May prior to the monsoon onset.Wind speed and shortwave flux emerge as key drivers, although wind speed exerts a stronger regional influence on diurnal warming. Furthermore, the SST diurnal variation responds to the MJO within 1-2 days, as its active phase increases cloud cover and intensifies wind, thereby suppressing daytime warming. Despite the high temporal resolution of FY-4A, which allows for detailed sub-daily observations, monsoonal circulation and cloud cover can reduce data availability, complicating quantitative studies of SST variability and MJO feedbacks. Therefore, integrating multiple data sources is crucial for comprehensive analyses. Overall, these findings underscore the potential of geostationary satellites for monitoring diurnal SST fluctuations and emphasize the necessity of accounting for complex atmospheric-oceanic interactions in the North Indian Ocean when examining the role of diurnal variation in broader climate processes.

Keywords: FY-4A 1, SST diurnal variation 2, the North Indian Ocean 3, diurnal warming 4, MJO 5

Received: 03 Mar 2025; Accepted: 30 Jun 2025.

Copyright: © 2025 Zhang, Zhihua, Zhang and Sang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mao Zhihua, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, Zhejiang Province, China

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