Localised 14 day composites of chlorophyll a

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Topic Products and Algorithms / Satellite Data Products & Algorithms / Localised 14 day composites of chlorophyll a (locked) (3435 hits)

By sharkwatch Date 2011-05-13 07:08

Hello,

I am new to the site and have been trying to put together 14 day compsites of cholorophyll-a levels for the Arabian Gulf and cannot seem to figure it out. Can somebody advise me how I can do this and at the highest possible resolution.

I have managed to get a monthly composite but cannot zoom in to see the Arabian Gulf at a high enough resolution.

Kind regards

David

By @sean Date 2011-05-16 13:47

David,

Your best bet would be to grab the L2 scenes that cover your region of interest and use the l2bin program
provided with SeaDAS to bin these files at a 2km resolution, e.g.:

l2bin infile=input_L2.lst ofile=my_l3bin.hdf resolve=2 prodtype=regional l3bprod=chlor_a

(You *could* bin at 1km, but may find that 14 days is insufficent to fill in the 'holes' and any map produced from
such a bin file may suffer the pinhole effect)

SeaDAS can read this L3 bin file for display/reprojection, or you could use smigen to create a 'standard' mapped image
from the bin file (which is also readable by SeaDAS - and can be used to create a ppm image file with smitoppm)

Regards,
Sean

By chen Date 2011-07-01 14:19

Sean,
I am trying to create 1km daily, weekly mean of oc, sst for the GOM using l2bin but the ofile has a lot of small black artifacts in the images. Do you know where the problem is ? By the way how I attached a file for you to see ?

BC

By @sean Date 2011-07-01 14:34

Bob,

As the instrument is only nominally 1km at nadir, binning to 1km will
introduce such artifacts. The only way to avoid it is to bin to lower
spatial resolutions, or higher temporal resolutions - or map the data
and interpolate.

Sean

By chen Date 2011-07-01 17:26

Sean,
Yes, monthly mean the artifacts went away. This will happen if the area you're interested is bigger than the "Local L2" coverage. For instance for GOM if I have a granule is farther away from the center I'll get artifacts from this grangule because l2bin projects this granule before the binning ? Can you suggest how you do the map an interploate for the case of binning daily images for GOM with 1KM resolution using L2 LAC files ?

BC

By chen Date 2011-07-11 15:26

Sean,
Two questions:
1. what are the differences between l2bin and bl2map ?
2. how I called the seadas pro from the shell script i.e. bl2map which is not in the seadas bin directory ?
Thanks !

BC

By @sean Date 2011-07-11 22:34

bl2map was written a originally just for SeaWiFS, though it has been modified to work with other sensors.
It produces a "SeaDAS mapped" file for any or all products in one or more L2 files.
The information stored in the resulting HDF file is very IDL map projection specific.
It's also on the deprecation list... don't ask for the full list - it's mostly in my head :-)

We are working on improvements to l2mapgen that will replicate the functionality of bl2map
without the limitations of the current output format.

l2bin is a binning program. It produces files as defined in the Level 3 product specs

bl2map is IDL code - to use it from the *nix command line, you'll need to wrap it in a seadas batch call.

Sean

Topic Products and Algorithms / Satellite Data Products & Algorithms / Localised 14 day composites of chlorophyll a (locked) (3435 hits)