Brief description
The Aqua satellite platform carries a MODIS sensor that observes sunlight reflected from within the ocean surface layer at multiple wavelengths. These multi-spectral measurements are used to infer the concentration of chlorophyll-a (Chl-a), most typically due to phytoplankton, present in the water. Modelling is then used to compute an estimate of the Net Primary Productivity (NPP).The model used is based on the standard vertically generalised production model (VGPM). The VGPM is a "chlorophyll-based" model that estimates net primary production from chlorophyll using a temperature-dependent description of chlorophyll-specific photosynthetic efficiency. For the VGPM, net primary production is a function of chlorophyll, available light, and the photosynthetic efficiency. The only difference between the Standard VGPM and the Eppley-VGPM is the temperature-dependent description of photosynthetic efficiencies, with the Eppley approach using an exponential function to account for variation in photosynthetic efficiencies due to photoacclimation. The similarity between these models (VGPM vs E_VGPM) is described more extensively in a paper by Elena-Carr et al (2006.). VGPM is a Depth Integrated Model(DIM) described by Behrenfeld and Falkowski (1997), with modification due to Eppley (1972) as implemented by Antoine and Morel (1996).
There are multiple retrieval algorithms for estimating Chl-a. These data (eppley_npp_chl_gsm) use the Garver-Siegel-Maritorena (GSM) method implemented in the SeaDAS processing software l2gen and described in “Chapter 11, and references therein, of IOCCG Report 5, 2006, (http://ioccg.org/wp-content/uploads/2015/10/ioccg-report-05.pdf). This product is recommended for use in the VGPM model. The product Eppley_NPP_chl_gsm is experimental, in the sense that it is challenging to validate due to the scarcity of insitu measurments. It should only be used with caution informed by understanding of the algorithms.
Lineage
Statement: The radiometric sensitivity of the MODIS sensor is evolving continuously during its mission and is monitored regularly by NASA. The SeaDAS software uses tables of calibration coefficients that are updated periodically. From time to time upgrades to the algorithms and/or the format of the calibration tables are required, in which case a new version of SeaDAS is released. These data were updated on 1 September 2020 to use processing in SeaDAS v7.5 and between 2002/07/04 and 2022/06/30 are consistent with the R2018.0 reprocessing (https://oceancolor.gsfc.nasa.gov/reprocessing/r2018/aqua/). Data between 2022/07/01-2023/01/31 and then from 2023/02/01 onwards, have been processed with two more recent releases of SeaDAS and are yet to be fully verified for consistency with NASA’s most recent processing(s). Once consistency has been established, the entire data set (from 2002/07/04) will be updated and this metadata record will be changed to reflect that. The data are produced by combining the near real time (nrt) data stream from all the available direct broadcast reception stations in Australia with delayed-mode data from NASA in the US. The data have been remapped from satellite projection into a geographic (Latitude/Longitude axes) projection (0.01 degree sampling) and are presented as a sequence of daily mosaics covering the region (80 <= Longitude <= 180, -60 <= Latitude <= +10) formatted as CF-compliant netCDF files. It should be noted that the data are not processed until the definitive spacecraft ephemeris becomes available, usually 12-24 hours after the overpass. This means that the geolocation should be of a uniformly high standard. The filenames are of the form A.P1D.Notes
CreditAustralia’s Integrated Marine Observing System (IMOS) is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS). It is operated by a consortium of institutions as an unincorporated joint venture, with the University of Tasmania as Lead Agent.
CSIRO Oceans and Atmosphere
Curtin University
Created: 04 11 2014
Data time period: 07 2002
text: westlimit=80; southlimit=-60.00; eastlimit=179.9; northlimit=10.00
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(Satellite Remote Sensing page on IMOS website)
uri :
http://imos.org.au/srs.html
SRS - OC GSM - WMS layer (srs_oc_aqua_npp_vgpm_eppley_gsm_url/npp_vgpm_eppley_gsm)
uri :
http://geoserver-123.aodn.org.au/geoserver/ncwms
(GoGoDuck help documentation)
uri :
https://help.aodn.org.au/web-services/gogoduck-aggregator/
(ncUrlList help documentation)
uri :
https://help.aodn.org.au/web-services/ncurllist-service/
- global : 27cc65c0-d453-4ba3-a0d6-55e4449fee8c