GSM

GSM Product Family Description

The ocean color products available here were made using Level 3, daily, binned imagery from SeaWiFS and MODIS-Aqua. The products themselves are 9km daily, weekly (8D) and monthly imagery of GSM products, confidence intervals and coverage maps. The products were generated using the Garver-Siegel-Maritorena (GSM) model described in:

Maritorena S., D.A. Siegel & A. Peterson. 2002. Optimization of a Semi-Analytical Ocean Color Model for Global Scale Applications. Applied Optics. 41(15): 2705-2714.

When multiple sensors are used, the GSM model uses the Normalized Water-Leaving radiances (LwNs) from all available sources over a given bin of the L3 grid as described in:

Maritorena, S. and D.A. Siegel. 2005. Consistent Merging of Satellite Ocean Color Data Sets Using a Bio-Optical Model. Remote Sensing of Environment, 94(4): 429-440.

Maritorena S., O. Hembise Fanton d’Andon, A. Mangin, D.A. Siegel. 2010. Merged Satellite Ocean Color Data Products Using a Bio-Optical Model: Characteristics, Benefits and Issues. Remote Sensing of Environment, 114, 8: 1791-1804 (doi: 10.1016/j.rse.2010.04.002).

File Naming convention:

---

For daily files:

Prod_name.YearDay.L3b_DAY.Sat_combo.Proc_vers.Type

where:

Prod_name:
----------

GSMchl	(Chlorophyll concentration)
GSMacdm	(Dissolved and detrital organic matter absorption coefficent at 443 nm)
GSMbbp	(Particulate backscattering coefficient at 443 nm)
GSMChl_sig	(Confidence interval of the Chl product)
GSMacdm_sig	(Confidence interval of the acdm product)
GSMbbp_sig	(Confidence interval of the bbp product)
GSMcovMask	(Coverage map)
GSMbin	all the above in bin-indexed format

Year:
----------
Year in yyyy format

Day:
----------
Day in ddd format (i.e. sequential day of the year)

Sat_combo:
----------
Describes which sensor or combination of sensors were used to produce the data:
SeaWiFS only = 01
MODIS-Aqua only = 02
SeaWiFS and Aqua = 03

Proc_vers:
----------
Refers to the version of the data (current processing is 5, associated with the R2009.1 reprocessing effort (http://oceancolor.gsfc.nasa.gov/forum/oceancolor/board_show.pl?bid=27)
Type:
----------
Describes the type of file (HDF or PNG)

Examples of daily file names:

---

GSMchl.2003121.L3b_DAY.01.4.hdf -> GSM chlorophyll product from SeaWiFS only L3b data for day 121 of 2003 (May 1, 2003), version 5

GSMacdm.2005021.L3b_DAY.03.2.hdf -> GSM acdm(443) product from SeaWiFS and MODIS-Aqua L3b data for day 21 of 2005 (January 21, 2005), version 5


For composite data:

Prod_name.SYearSDayEYearEDay_ID.Sat_combo.Proc_vers.Type

Prod_name:
----------
same as for daily except no GSMcovMask. In the GSMbin product the covMask SDS is replaced with the number of pixels composited.

Definitions of Sat_combo, Proc_vers and Type are identical to those for the daily files.

YearFDayYearLDay:
----------
Year (in yyyy format)
First day (in ddd format, i.e. sequential day of the year) of daily data used to create the composite image.
Year (in yyyy format)
Last day (in ddd format) of daily data used to create the composite image.

_ID:
----------

is "_4D" for four-day, "_8D" for weekly, and "_MO" for Monthly data

Examples of composite image names:

---

GSMchl.20030012003031_MO.03.5.hdf -> Monthly GSM chlorophyll product from SeaWiFS and Aqua data for January 2003, version 5

GSMbbp.20050812005088_8D.02.5.hdf -> Weekly GSM bbp(443) product from Aqua only data (March 22-29, 2005), version 5

The data products are available in HDF (Hierarchical Data Format) files. Each product is represented in a 4320 x 2160 array. For each time period considered (Day, 8D, Monthly) there is one HDF file per product. HDF files are compressed and will self extract when opening. PNG images are also available for browsing purposes.

Product Units:

---

GSMchl	mg m-3
GSMacdm	m-1
GSMbbp	m-1
GSMchl_sig	mg m-3
GSMacdm_sig	m-1
GSMbbp_sig	m-1

Data (links to FTP site)

• SeaWiFS

• MODIS Aqua

• Merged

Metadata

• GSM01 Validation Results (TBA)

• (recent results TBA)

Software

• GSM Code (IDL)

References

Maritorena, S., and D.A. Siegel, 2005: Consistent merging of satellite ocean color data using a semi-analytical model, Remote Sensing of the Environment, 94, 429-440.pdf

Siegel, D.A., Maritorena, S., Nelson, N.B., Hansell, D.A., Lorenzi-Kayser, M., 2002. Global distribution and dynamics of colored dissolved and detrital organic materials. Journal of Geophysical Research, 107, 3228, doi:10.1029/2001JC000965. pdf

Maritorena, S., D.A. Siegel and A.R. Peterson, 2002: Optimization of a semianalytical ocean color model for global-scale applications. Applied Optics-LP, 41, 2705-2714. pdf

Garver, S.A., and D.A. Siegel, 1997: Inherent optical property inversion of ocean color spectra and its biogeochemical interpretation: I. Time series from the Sargasso Sea. Journal of Geophysical Research., 102, 18,607-18,625. pdf