Abstract:
This data set consists of satellite measurements of global ocean color data
obtained by the Moderate Resolution Imaging Spectroradiometer (MODIS), in orbit
on the Aqua (formerly EOS PM) platform. MODIS ocean color products are
processed and distributed by the Ocean Biology Processing Group (OBPG).
Processing details can be found at
http://oceancolor.gsfc.nasa.gov/DOCS/MODISA_processing.html Each
... Level-2 Local Area Coverage (LAC) product is generated from a
corresponding Level-1B product. The main data contents of the product are the
geophysical values for each pixel, derived from the Level-1B radiances by
applying the atmospheric corrections and bio-optical algorithms. Each Level-2
product corresponds exactly in geographical coverage (scan-line and pixel
extent) to that of its parent Level-1B product and is stored in one physical
HDF file. The resolution is the same as the corresponding level 1B file (1
km).
The standard Ocean Color product contains the following geophysical values
derived for each pixel:
-Normalized water-leaving radiances at 412, 443, 488, 531, 551 & 667 nm
-Chlorophyll a concentration
-Diffuse attenuation coefficient at 490 nm (measure of optical clarity)
-Epsilon of aerosol correction at 748 and 869 nm
-Angstrom coefficient, 531 to 869 nm (for atmospheric correction)
-Aerosol optical thickness at 869 nm (for atmospheric correction)
In addition, 32 flags are associated with each pixel indicating if any
algorithm failures or warning conditions occurred for that pixel.
Detailed information on the Level-2 format specifications can be found at
http://oceancolor.gsfc.nasa.gov/DOCS/Ocean_Level-2_Data_Products.pdf
Level-2 processing is performed using the Multi-Sensor Level-1 to Level-2
(MSl12) code, which is developed and maintained by the OBPG. MSL12 is used for
the standard processing of all ocean products distributed through the web
browsers and FTP sites. This software is capable of retrieving oceanic optical
properties and various derived products from the observed top-of-atmosphere
(TOA) radiances collected by a variety of ocean remote sensing radiometers,
including MODIS. Full documentation, updated code source, sensor files, and
output product descriptions can be found at
http://oceancolor.gsfc.nasa.gov/DOCS/MSL12/. For MODIS, the Level-1B file and
the GEO file for each 5-minute granule are input to MSl12.
The Level-2 processing also makes use of meteorological and ozone information
from ancillary sources. In the near real-time (NRT) stream, climatological
meteorological and ozone data are used. The NRT Quick Look products are then
immediately available on the web browser and in the rolling FTP archive within
6-10 hours of observation. When the definitive attitude and orbit and
coincident meteorological and ozone data are received several days later, they
are used in the Refined processing stream, and the Level-2 products are
regenerated.
Please, read the MODIS Ocean Parent document for more details:
http://gcmd.nasa.gov/getdif.htm?MODIS_OCEAN_PARENT
Browse Level 2 Data at http://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sen=am
Aqua MODIS Level-2 daytime data for the most-recent days can be downloaded by
FTP at ftp://oceans.gsfc.nasa.gov/MODISA/Recent_Day/
Aqua MODIS Level-2 nighttime data for the most-recent days can be downloaded by
FTP at ftp://oceans.gsfc.nasa.gov/MODISA/Recent_Night/ 
