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Validation of OCM-3 chlorophyll-a in the Eastern Arabian Sea using in situ measurements: a comparative analysis with MODIS-Aqua, VIIRS, and Sentinel-3B.

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Title: Validation of OCM-3 chlorophyll-a in the Eastern Arabian Sea using in situ measurements: a comparative analysis with MODIS-Aqua, VIIRS, and Sentinel-3B.
Authors: Vennila, Murugan1 (AUTHOR), Manimozhi, Nagarajan1 (AUTHOR), Sarangi, Ranjt Kumar2 (AUTHOR), Gopinath, Anu1 (AUTHOR) dranugopinath@gmail.com, Singh, Sambit1 (AUTHOR), Minu, P1 (AUTHOR)
Source: Journal of Earth System Science. Sep2026, Vol. 135 Issue 3, p1-18. 18p.
Subject Terms: *Chlorophyll, *MODIS (Spectroradiometer), *Artificial satellites, *Phytoplankton populations
Geographic Terms: Arabian Sea
Abstract: Chlorophyll-a (Chl-a) is a primary photosynthetic pigment of oceanic phytoplankton, which plays a crucial role in determining the colour of seawater. Consequently, estimation of Chl-a is a key indicator for monitoring phytoplankton biomass and marine ecosystem health. In this context, the present study evaluates the performance of the newly launched Indian satellite Ocean Colour Monitor-3 (OCM-3) sensor onboard EOS-06/Oceansat-3, in estimating surface Chl-a concentrations, in comparison with other global ocean colour sensors, MODIS-Aqua, VIIRS, and Sentinel-3B, in the Eastern Arabian Sea (EAS) during the late-winter monsoon. In situ Chl-a data collected from 63 stations during a ship cruise onboard CRV Sagar Tara were compared with satellite-derived Chl-a. Statistical metrics such as RMSE, bias, slope, R2, and uncertainty indices (MAPD, MRPD, UPD) were employed to assess sensor accuracy. Chl-a concentrations varied across the EAS, higher in the North Eastern Arabian Sea (NEAS) (2.60 ±1.06 mg/m3) compared to the South Eastern Arabian Sea (SEAS) (0.78 ± 0.50 mg/m3). The high Chl-a concentration in the NEAS is attributed to the impact of convective mixing and nutrient enrichment. From this study, the performance of sensor assessment shows that MODIS-Aqua has a higher correlation (r = 0.71) and accuracy in Chl-a distribution followed by OCM-3, VIIRS, and Sentinel-3B along the EAS. In particular, the OCM-3 showed performance comparable to MODIS-Aqua in mesotrophic (0.5–1 mg/m3) Chl-a distribution in the EAS, characterized by a low RMSE (0.432), although with a relatively higher bias compared to MODIS-Aqua. The OCM-3 showed a systematic overestimation of low Chl-a (<0.5 mg/m3) and a consistent underestimation of high Chl-a (>1 mg/m3), particularly in optically complex coastal waters influenced by total suspended matter (TSM) and coloured dissolved organic matter (CDOM). This study revealed that the OCM-3 Chl-a need to be evaluated further with an extensive dataset around the EAS to improve the regional algorithms for accurate measurements of Chl-a. Research highlights: Chl-a concentration was higher in the North Eastern Arabian Sea (NEAS) than the South Eastern Arabian Sea (SEAS) during the late-winter monsoon. The high Chl-a observed in the NEAS was primarily driven by convective mixing. OCM-3 sensor showed performance comparable to MODIS-Aqua in mesotrophic waters (0.5–1 mg/m3), with low RMSE but relatively higher bias. The OCM-3 showed a systematic overestimation of low Chl-a (<0.5 mg/m3) and a consistent underestimation of high Chl-a (>1 mg/m3). [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
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DbLabel: Energy & Power Source
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  Label: Title
  Group: Ti
  Data: Validation of OCM-3 chlorophyll-a in the Eastern Arabian Sea using in situ measurements: a comparative analysis with MODIS-Aqua, VIIRS, and Sentinel-3B.
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  Label: Authors
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  Data: &lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Vennila%2C+Murugan%22&quot;&gt;Vennila, Murugan&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Manimozhi%2C+Nagarajan%22&quot;&gt;Manimozhi, Nagarajan&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Sarangi%2C+Ranjt+Kumar%22&quot;&gt;Sarangi, Ranjt Kumar&lt;/searchLink&gt;&lt;relatesTo&gt;2&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Gopinath%2C+Anu%22&quot;&gt;Gopinath, Anu&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)&lt;i&gt; dranugopinath@gmail.com&lt;/i&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Singh%2C+Sambit%22&quot;&gt;Singh, Sambit&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Minu%2C+P%22&quot;&gt;Minu, P&lt;/searchLink&gt;&lt;relatesTo&gt;1&lt;/relatesTo&gt; (AUTHOR)
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  Data: &lt;searchLink fieldCode=&quot;JN&quot; term=&quot;%22Journal+of+Earth+System+Science%22&quot;&gt;Journal of Earth System Science&lt;/searchLink&gt;. Sep2026, Vol. 135 Issue 3, p1-18. 18p.
– Name: Subject
  Label: Subject Terms
  Group: Su
  Data: *&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Chlorophyll%22&quot;&gt;Chlorophyll&lt;/searchLink&gt;&lt;br /&gt;*&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22MODIS+%28Spectroradiometer%29%22&quot;&gt;MODIS (Spectroradiometer)&lt;/searchLink&gt;&lt;br /&gt;*&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Artificial+satellites%22&quot;&gt;Artificial satellites&lt;/searchLink&gt;&lt;br /&gt;*&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Phytoplankton+populations%22&quot;&gt;Phytoplankton populations&lt;/searchLink&gt;
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  Label: Geographic Terms
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  Data: &lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Arabian+Sea%22&quot;&gt;Arabian Sea&lt;/searchLink&gt;
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Chlorophyll-a (Chl-a) is a primary photosynthetic pigment of oceanic phytoplankton, which plays a crucial role in determining the colour of seawater. Consequently, estimation of Chl-a is a key indicator for monitoring phytoplankton biomass and marine ecosystem health. In this context, the present study evaluates the performance of the newly launched Indian satellite Ocean Colour Monitor-3 (OCM-3) sensor onboard EOS-06/Oceansat-3, in estimating surface Chl-a concentrations, in comparison with other global ocean colour sensors, MODIS-Aqua, VIIRS, and Sentinel-3B, in the Eastern Arabian Sea (EAS) during the late-winter monsoon. In situ Chl-a data collected from 63 stations during a ship cruise onboard CRV Sagar Tara were compared with satellite-derived Chl-a. Statistical metrics such as RMSE, bias, slope, R2, and uncertainty indices (MAPD, MRPD, UPD) were employed to assess sensor accuracy. Chl-a concentrations varied across the EAS, higher in the North Eastern Arabian Sea (NEAS) (2.60 &#177;1.06 mg/m3) compared to the South Eastern Arabian Sea (SEAS) (0.78 &#177; 0.50 mg/m3). The high Chl-a concentration in the NEAS is attributed to the impact of convective mixing and nutrient enrichment. From this study, the performance of sensor assessment shows that MODIS-Aqua has a higher correlation (r = 0.71) and accuracy in Chl-a distribution followed by OCM-3, VIIRS, and Sentinel-3B along the EAS. In particular, the OCM-3 showed performance comparable to MODIS-Aqua in mesotrophic (0.5–1 mg/m3) Chl-a distribution in the EAS, characterized by a low RMSE (0.432), although with a relatively higher bias compared to MODIS-Aqua. The OCM-3 showed a systematic overestimation of low Chl-a (&lt;0.5 mg/m3) and a consistent underestimation of high Chl-a (&gt;1 mg/m3), particularly in optically complex coastal waters influenced by total suspended matter (TSM) and coloured dissolved organic matter (CDOM). This study revealed that the OCM-3 Chl-a need to be evaluated further with an extensive dataset around the EAS to improve the regional algorithms for accurate measurements of Chl-a. Research highlights: Chl-a concentration was higher in the North Eastern Arabian Sea (NEAS) than the South Eastern Arabian Sea (SEAS) during the late-winter monsoon. The high Chl-a observed in the NEAS was primarily driven by convective mixing. OCM-3 sensor showed performance comparable to MODIS-Aqua in mesotrophic waters (0.5–1 mg/m3), with low RMSE but relatively higher bias. The OCM-3 showed a systematic overestimation of low Chl-a (&lt;0.5 mg/m3) and a consistent underestimation of high Chl-a (&gt;1 mg/m3). [ABSTRACT FROM AUTHOR]
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=enr&AN=195596264
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1007/s12040-026-02828-x
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 18
        StartPage: 1
    Subjects:
      – SubjectFull: Chlorophyll
        Type: general
      – SubjectFull: MODIS (Spectroradiometer)
        Type: general
      – SubjectFull: Artificial satellites
        Type: general
      – SubjectFull: Phytoplankton populations
        Type: general
      – SubjectFull: Arabian Sea
        Type: general
    Titles:
      – TitleFull: Validation of OCM-3 chlorophyll-a in the Eastern Arabian Sea using in situ measurements: a comparative analysis with MODIS-Aqua, VIIRS, and Sentinel-3B.
        Type: main
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          Name:
            NameFull: Vennila, Murugan
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            NameFull: Manimozhi, Nagarajan
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            NameFull: Sarangi, Ranjt Kumar
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            NameFull: Gopinath, Anu
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            NameFull: Singh, Sambit
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            NameFull: Minu, P
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            – D: 01
              M: 09
              Text: Sep2026
              Type: published
              Y: 2026
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              Value: 02534126
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              Value: 135
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            – TitleFull: Journal of Earth System Science
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