Marine Data Literacy 2.0

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Home > 9. Operational/Synoptic > 9.25 Prime Prod

9.25 Visualizing Satellite-Measured Primary Production in IDV: OceanWatch

  • Exercise Title:  Visualizing Satellite-Measured Primary Production in IDV: OceanWatch

  • Abstract: "NOAA CoastWatch provides a measurement of primary productivity based on the following satellite measurements: photosynthetically available radiation (PAR) values derived from the SeaWiFS sensor aboard the Orbview-2 satellite, chlorophyll-a concentration from the MODIS sensor on NASA's Aqua satellite, and SST measurements from the NOAA Pathfinder Project and from the Reynolds Optimally-Interpolated SST (OISST) v2 product from NOAA's National Climatic Data Center (NCDC). In the surface ocean, net primary productivity is the amount of organic carbon generated by photosynthesis in planktonic organisms minus the amount of organic carbon used by these organisms in respiration. Primary producers form the base of the food chain and generate the biomass that sustains all life in the ocean. NOAA CoastWatch Primary Productivity is an EXPERIMENTAL dataset, distributed for scientific evaluation." [Text from the THREDDS dataset summary provided by the data publishers.]  The references to "CoastWatch" are due to a transition now underway from the CoastWatch system to the new OceanWatch system of products.  This very complex Level-4 product is a state-of-the-art estimation, based on the work of Behrenfeld and Falkowski, using three operational sources and one climatology. 

  • Preliminary Reading (in OceanTeacher, unless otherwise indicated):

  • Required Software:

  • Other Resources: 

    • N/A

  • Author:  Murray Brown

  • Version:  December 2012

IMPORTANT NEW INFORMATION:  Recently the Saga GIS software has been shown to deal quite adequately with most NetCDF (NC) data grids (and possibly also GRIB files).  This should be viewed as a useful addition to the rapid, direct NC analysis and display capabilities of IDV (see below).  If you are also interested in this route for your data, then please check Viewing and Managing Well-Formed NetCDF Grids in Saga.
1.  At the outset we need to make clear that there is no "primary productivity sensor" on any satellite, so the title of this exercise is slightly misleading.  This exercise accesses and displays high-level analyses that depend on data from multiple sensors (on multiple platforms!) to calculate primary production.
2.  Run IDV.
4.  Navigate down into the color menu to find the primary productivity product based on AquaMODIS and Pathfinder data.  Read the DATASET SUMMARY to see how complicated this product is.  Then select the 8-DAY product.  Then click on ADD SOURCE.

NOTE:  The GOES- and SeaWIFS-related products just above and below the PATHFINDER-related product are no longer created.

NOTE2:  Although we are focusing here on operational products, you can see that a "monthly" product is also available.  You can see what this looks like, compared to the 8-day product, at the bottom of the exercise

5.  Here are the default settings you see initially.  Before you can click CREATE DISPLAY, you must make some properties settings.
6.  Find the 8-DAY product in the data sources list.  Right-click on it and select PROPERTIES.
7. Check all 5 tabs to see what they refer to.
8.  Select the TIMES tab.  Then select USE SELECTED.  Then scroll down to the most recent product and select it.
9.  Find the SPATIAL SUBSET tab.
10.  To activate this tab, first draw a small rectangle anywhere on the map.
11.  Now enter the correct values for the limits of our Liberia area of interest in the control boxes.

Then click OK.

12.  Now you can select DISPLAYS > PLAN VIEWS > COLOR-SHADED PLAN VIEW to get the desired map.


13.  This map appears.  Notice that the color palette could be better.
14.  Examine the dashboard for this map, and you will see the controls you need for data value and for the color palette.

Note that the value range for the data goes from 135 to 7497, and the units are mg C m-2 day-1.

17.  Here are the upper and lower data values in the actual dataset.  We could change them to "round numbers" to look better.
18.  Change them as shown here.  Then click OK.
19.  Just for a reality-check, here's a calculation of the global average primary production value.  It's based on the global value in the Wikipedia article above, which uses data from the authors of this CoastWatch data product.
  • 140 g C/m^2/yr
  • 140000 mg C/m^2/yr
  • 384 mg C/m^2/day

So we see that real-world values (probably in the coast) can be up to 20X the average.

20.  So here's the map of the 8-day product.  You can just see an area of high production along the coast, and evidence of meso-scale areas offshore.  Unfortunately the 8-day window is badly contaminated with clouds, which is a common problem in the tropics.
21.  Just for comparison, here's the monthly product, mentioned in Panel 4 above.  It probably makes sense to accept the long delay for this product, balanced against the much more complete coverage.
22.  You can select SAVE AS and navigate to the folder PRODUCTS > IDV to save these products (together, if you have both) with the filename prim_prod_201212_liberia_coastwatch.xidv