phycocyanin data

[mikewong]

Hello, I want to access satellite-observed bloom data for phycocyanin. I'm trying to follow the equation presented in Zhang et al. Environmental Health (2015) 14:41, which used pure water absorption at 665 and 709 nm. Could someone please advice me on acquiring this data from EarthData? If anyone knows of other methods, those are also welcomed. Much appreciated!

[OB SeaBASS - cwproctor]

I am not an expert on the manuscript you referenced, but here are a few thoughts to hopefully get you started. I believe the authors used Level-1B MERIS data, which you can find how to download from https://oceancolor.gsfc.nasa.gov/data/find-data/ . Either File Search, Level 1 & 2 Browser, or Earthdata Search will yield the data you're looking for; all are fine options, it just depends which interface you prefer.

Level-1B files contain the underlying information necessary to generate absorption measurements, though it is necessary to use additional software to process the files (i.e., to become Level-2). This step allows for an enormous amount of customization in processing settings, but for those unfamiliar with the workflow, it will take time and effort. You might consider starting with Level-2 files. You'd probably want Inherent Optical Properties (IOPs) Level 2 files which contain total absorption coefficients, etc. https://oceancolor.gsfc.nasa.gov/resources/atbd/giop/ . However, you should refer to the processing settings the authors used to understand a) if the standard NASA Level 2 files contain all the products you want, and b) how the authors might have used custom settings that will result in differences from the NASA versions.

More on understanding different satellite data Levels:
https://oceancolor.gsfc.nasa.gov/resources/docs/product-levels/

Also, this might or might not be useful to you, but for your situation awareness here is a link to the Cyanobacteria Assessment Network (CyAN) project:
https://oceancolor.gsfc.nasa.gov/about/projects/cyan/

[OB General Science - guoqingw]

Adding to Chris's reply, there are several different sets of pure water absorption coefficients from lab measurements. It appears the authors didn’t cite the corresponding article in that publication. The best way to obtain the exact same data is by contacting the authors.

However, the coefficients used in our standard L2 IOPs retrievals are from Pope and Fry (1997). More details are available in this ATBD: https://oceancolor.gsfc.nasa.gov/resources/atbd/giop/.