The Benguela merged satellite-derived 4-km dataset

Mati Kahru, mkahru@ucsd.edu                                                                 Updated : 6/14/2015

A merged 4-km dataset using data from multiple satellite sensors has been created for the Benguela region. The methods follow the methods described for the similar California Current dataset  http://spg.ucsd.edu/Satellite_Data/CC4km/CC4km.htm.

 

C20030012003005_chl_comp_interpolated_3_interpolated_3.hdf

Fig. 1. An example of a 5-day Chla product of January 1-5, 2003 (left), the interpolated 5-day (middle) and the 2x interpolated (right) 5-day product.

The datasets are in Zipped files and can be downloaded using the following hyperlinks:

Chla Daily

Chla Daily

Chla Daily

Other

1996

2003

2010

Chla 5-day all years

1997

2004

2011

Chla 5-day interpolated

1998

2005

2012

Chla 5-day interpolated 2x

1999

2006

2013

 Chla monthly ;            Chla monthly PNG files

2000

2007

2014

 

2001

2008

2015

SST-OI 5-day 1981-2016, HDF4 files ; SST-OI 5-day 1981-2016, PNG files

2002

2009

2016

SST-OI monthly 1981-2016 ; SST monthly 2000-2016

 

 

 

 

NPP Daily

NPP Daily

NPP Daily

Other

1996

2003

2010

Net Primary Production monthly

1997

2004

2011

 

1998

2005

2012

 

1999

2006

2013

 

2000

2007

2014

 

2001

2008

2015

 

2002

2009

2016

 

 

The datasets on a grid of 540 (width) x 417 (height) with approximately 4000 m step are in HDF4 format.  The upper-left corner (lat, lon) is -25N; 6E; the lower-right corner is -38.9641N; 27.95769E. Chla values in each pixel of unsigned byte are log10-scaled and can be calculated from the pixel value (PV) as: Chl (mg m-3) = 10^(0.015 * PV - 2.0), i.e. 10 to the power of 0.015 * PV - 2.0. Pixel values 0, 1 (black in Fig. 1) and 255 (white in Fig. 1) are considered invalid and must be excluded from any statistics.  PV = 1 is used for coastline and has to be excluded too. The annotation (color bar) is written into the dataset. When reading with Matlab the unsigned byte variable is sometimes reported as signed byte (int8, values from -127 to 128) and not as unsigned byte (values from 0 to 255) and values over 128 become negative. A simple fix is to add 256 if the signed pixel value is negative.

The SST data are converted from the global AVHRR OI dataset (http://podaac.jpl.nasa.gov/dataset/NCDC-L4LRblend-GLOB-AVHRR_OI ) and use the same scaling as  in the full resolution dataset (http://spg.ucsd.edu/Satellite_Data/California_Current/Readme.htm).