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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Remote sensing NPP |- | '''Approach:''' satellite ocean colour and NPP models |- | '''Context:''' remote sensing (satellite) |- | '''Spatial scale:''' 0.5–4 km pixel; global coverage |- | ''..."

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Created page with "{{BreadcrumbsPrimaryProduction}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- __TOC__ <div class="model-box"> {| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Remote sensing NPP |- | '''Approach:''' satellite ocean colour and NPP models |- | '''Context:''' remote sensing (satellite) |- | '''Spatial scale:''' 0.5–4 km pixel; global coverage |- | ''..."

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{{BreadcrumbsPrimaryProduction}}

* [[Page authors|Page authors]]: [[PRIMO]]
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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Remote sensing NPP
|-
| '''Approach:''' satellite ocean colour and NPP models
|-
| '''Context:''' remote sensing (satellite)
|-
| '''Spatial scale:''' 0.5–4 km pixel; global coverage
|-
| '''Temporal scale:''' days to years
|-
| '''Units:''' mg C m<sup>-2</sup> d<sup>-1</sup>
|-
| '''Community captured:''' bulk
|-
| '''Co-measurements:''' remote sensing reflectance (Rrs), PAR, sea surface temperature, mixed layer depth
|}
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== Method Overview ==

Satellite ocean colour sensors (e.g., MODIS, SeaWiFS, OLCI) measure the spectral radiance leaving the ocean surface in multiple visible and near-infrared bands. Bio-optical algorithms convert remote sensing reflectance (Rrs) into chlorophyll-a concentration and, in some models, the backscattering coefficient as a proxy for phytoplankton carbon (C<sub>phyto</sub>). NPP models then combine these biological proxies with satellite-derived PAR, sea surface temperature, and mixed layer depth estimates to calculate depth-integrated NPP<ref name="Westberry2023">Westberry, T. K., Silsbe, G. M., & Behrenfeld, M. J. (2023). Gross and net primary production in the global ocean: an ocean color remote sensing perspective. ''Earth-Science Reviews'', 237, 104322. https://doi.org/10.1016/j.earscirev.2023.104322</ref>.

Major NPP model classes include the Vertically Generalised Production Model (VGPM; chlorophyll-based), the Carbon-based Productivity Model (CbPM; phytoplankton carbon-based), and absorption-based models. Each uses a different formulation of the relationship between biomass, physiology, and carbon fixation.

=== Scale of measurement ===

Satellite pixels are typically 0.5–4 km; global coverage is achieved every 1–4 days depending on orbit and cloud cover. The optical signal originates from the surface euphotic layer only (approximately the first attenuation length). Depth integration of NPP is achieved through models rather than direct measurement.

=== Data generated ===

Depth-integrated NPP in mg C m<sup>-2</sup> d<sup>-1</sup>; time series enable seasonal and interannual trend analysis at regional to global scales.

=== Units & currency ===

Units are mg C m<sup>-2</sup> d<sup>-1</sup>. The currency is carbon.

=== Sample size ===

No sample collection required; the satellite measures upwelling radiance over a pixel footprint of km<sup>2</sup>.

=== Repositories & databases ===

Global satellite NPP products are distributed by NASA Ocean Color: [https://oceancolor.gsfc.nasa.gov/ oceancolor.gsfc.nasa.gov].

== Limitations ==

Satellite reflectance is limited to the optically accessible surface layer and cannot directly sense NPP below the first attenuation depth. Cloud cover creates temporal gaps requiring interpolation. Algorithm uncertainties in Rrs-to-chlorophyll conversion, the chlorophyll-to-carbon fixation relationship, and NPP model structure propagate into NPP estimates. Cross-mission biases require careful inter-calibration. Validation against direct measurements (e.g., <sup>14</sup>C) shows large regional uncertainties in models.

== Example Applications & Protocols ==

=== Classic examples ===
* Westberry et al. (2023) ''Gross and net primary production in the global ocean: an ocean color remote sensing perspective'' <ref name="Westberry2023" />

=== Recent applications ===
*

=== Common calculations/conversions ===
* NPP (mg C m<sup>-2</sup> d<sup>-1</sup>) = ∫ C<sub>phyto</sub>(z) × µ(z) dz; where µ is the phytoplankton-specific growth rate modelled from temperature and irradiance.

== References ==

[[Category:Main Pages|Model types]]

Remote Sensing NPP - Revision history