ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Ocean Observation
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1570854
INCOIS Air-Sea Flux Reference System (INCOIS-FRS) onboard ORV Sagar Nidhi: Overview and Initial Results
Provisionally accepted
B. Praveen Kumar1*
Abhijith Raj1,2
Asish K Sasidharan1,2N Sureshkumar1
A. A Gnanaraj3Deepak Sankar3K Ramsundar3Venkata Jampana1E. Pattabhi Rama Rao1- 1Indian National Centre for Ocean Information Services, Hyderabad, India
- 2Kerala University of Fisheries and Ocean Studies, Kochi, Kerala, India
- 3National Institute of Ocean Technology, Chennai, Tamil Nadu, India
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Accurate estimation of air-sea fluxes is essential for advancing ocean modeling, observational studies, and understanding air-sea interactions. To address this need, the Indian National Centre for Ocean Information Services (INCOIS) developed and deployed a Flux Reference System (INCOIS-FRS) onboard ORV Sagar Nidhi. This article provides an overview of the system, its components, data acquisition methods, flux computation techniques, and preliminary results. The INCOIS-FRS integrates an Eddy Covariance Flux System (ECFS) and an Automated Weather Station (AWS). The ECFS collects high-frequency (20 Hz) data to directly estimate the latent heat flux (LHF), sensible heat flux (SHF), and momentum flux (τ) using the Eddy Covariance (EC) method. The AWS records meteorological and oceanic variables at 1 Hz, enabling flux estimates using the COARE 3.5 algorithm. A spectrally flat Class-A pyranometer and a pyrgeometer provide climategrade measurements of downward shortwave and longwave radiation, which, combined with ECderived SHF and LHF, yield the net heat flux. This article presents preliminary results inferred from data collected by INCOIS-FRS during a cruise in the Arabian Sea from 1-16 July 2023. Data from this system are useful for validating model outputs and satellite observations, refining flux parameterizations, marine boundary layer studies, and improving air-sea interaction models. INCOIS-FRS represents a first step toward equipping more oceanographic platforms, both crewed and uncrewed, with flux reference units. Future plans include expanding such deployments to enhance observational coverage and support research on air-sea fluxes across the Indian Ocean and other regions.
Keywords: flux reference system, eddy covariance, Automated weather station, Air-sea fluxes, INCOIS-FRS
Received: 04 Feb 2025; Accepted: 08 May 2025.
Copyright: © 2025 Kumar, Raj, Sasidharan, Sureshkumar, Gnanaraj, Sankar, Ramsundar, Jampana and Rama Rao. 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: B. Praveen Kumar, Indian National Centre for Ocean Information Services, Hyderabad, India
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