Aqua Chl and STT L3 Processing Changes?

[mta45]

Hello,

I tried to search for this, but had no luck. Did the AQUA-Modis L3 Monthly Chlorophyll and Sea Surface Temperature files (from here: https://oceandata.sci.gsfc.nasa.gov/l3/) change or get reprocssed? The file names appear to be different and the values appear difference as well.

Thanks!

[OB ODPS - towens]

The CHL files were reprocessed in 2022.

Details of the file name changes:
https://oceancolor.gsfc.nasa.gov/resources/docs/filenaming-convention/

Can you be more specific about the value changes you are seeing?

Tommy

[mta45]

That is helpful and likely explains it.

Here's an example, where I compared the same data product that I had already downloaded previously, with the new one that has a different naming convention. They have different minimum and maximum values.

> library(terra)
terra 1.8.42
> existing <- rast("~/Downloads/AQUA_MODIS.20231201_20231231.L3m.MO.CHL.x_chlor_a.nc")
> new <- rast("~/Downloads/AQUA_MODIS.20231201_20231231.L3m.MO.CHL.chlor_a.4km.nc")
> global(existing, range, na.rm = TRUE)
X1 X2
chlor_a 0.001466351 86.33375
> global(new, range, na.rm = TRUE)
X1 X2
chlor_a 0.001257859 86.02554

[OB ODPS - towens]

The products were reprocessed with the latest chlor_a algorithm, so changes of that scale would not be unexpected.

Tommy