Full-resolution satellite time series of the Crozet Islands area

Mati Kahru, mkahru@ucsd.edu




  • Level-2 full-resolution datasets (both MLAC and GAC) of SeaWiFS were mapped and composited over time for the Crozet Islands region in the Southern Ocean. Currently only years 2001, 2002 and 2003 are processed. Data from other sensors (MODIS-Aqua: 2002-present,  MODIS-Terra: 2005-present and MERIS) are also available for data merger but were not used. The target map with 1-km resolution is from 50 to 40 degrees South and from 45 to 65 degrees East in linear projection (1572 x 1114 pixels).

  • Wimsoft (http://wimsoft.com) software was used. A tutorial for a similar project is available here.

  • Temporal composites were made at 1 day, 5 days, 15 days and 1 month intervals. Other periods of compositing and running averages can be constructed from the daily composites.

  • The processed files are available from http://spg.ucsd.edu/Satellite_data/Crozet/. Please note that the files are not available through FTP but through HTTP. For downloading multiple files at once you can use the widely available utility wget (e.g. http://www.gnu.org/software/wget/).


  • Related projects are producing full-resolution merged satellite data for the California Current and Scotia Sea areas (http://spg.ucsd.edu/Satellite_Projects/Full_res_sat_time_series_California/Full_res_sat_time_series_California.htm and http://spg.ucsd.edu/Satellite_Data/Scotia_Sea/)

  • GAC and MLAC data were merged with MLAC having higher priority, i.e. if MLAC pixel existed from the same day then it was used. If no MLAC data were available for a day then GAC data were used. For each of the composites three files were created: HDF, HDF annotated and PNG. The HDF files have the numerical values for each pixel and can be used to generate statistics for any selected area. The HDF files can be read with any HDF-aware software (e.g. Matlab, IDL, and WIM). When read with WIM the geo-location and scaling are automatically retrieved. 


         The following example is a monthly composite for January, 2003 showing high Chl-a near the islands and the meandering front north of the islands. The Chl-a concentration scale is logarithmic from 0.05 to 10 mg m-3.