Recently, I’m trying to get chlorophyll values from level-3 bin products.
According to SeaWiFS Technical Report Vol. 32, the equation used to calculate the mean value of variable is:
mx = S1 / w
square(Sx) = S2 / w – square(mx)
Xmle = exp( mx + ½ * square(Sx) );
I assume that S1 is sum and S2 is sum_square . When I applied this equation, the results seem not right (e.g. maximum value can reach 10e11, all values are above 1). In contrast, If I remove exp, the results are more reasonable but which is not mentioned in NASA report. Could you give me some instructions about this question. Are other variables such as PIC being applied a log calculation as well?
If you are writing your own software, note that calculations of the number of bins in each latitude band can give slightly different numbers if the latitudes are not computed exactly as done in the NASA software. This is more of a problem when the bins are small.
Thanks for your reply. I am used to using MATLAB and C to process datasets. In my case, I just wrote a script in MATLAB to calculate parameters including lat/lon and chlor_a for each bin. I have not installed virtual machine in my windows and no experience of using the OCSSW. I'm not sure whether the OCSSW software is flexible to be used on a time series study. Whatever, I would have a look at those sources. Hope to find my answer.
WSL gives you a bash shell in a terminal, which is all you need to install and run the OCSSW software. You will find it helpful to verify your Matlab results against the OCSSW software using
l3mapgen. The source code is of course the up-to-date documentation. In Windows you could also just download the source as a git bundle as described in OCSSW. Once you have unpacked the bundle do a "
git pull" to get any changes.
With minor tweaks the NASA IDL scripts should run under GNU Data Language (GDL) for Windows.
I have used
l3bindumpon (linux and macOS) many times to create ASCII files for a list of bins or region-of-interest for time-series processing. Linux (or macOS) is generally faster than Windows when running loops in scripts. I only use WSL2 for one-off calculations where speed isn't critical as it is much slower than native linux.
Thanks for sharing your experience.