Abstract
Ocean modellers use bathymetric data sets like ETOPO5 and ETOPO2 to represent
the bottom topography. The former data set is based on digitization of depth
contours greater than 200 m, and the latter is based on satellite altimetry.
Hence, they are not always reliable in shallow regions. An improved shelf bathymetry
for the Indian Ocean region (20°E to 112° E and 38°S to 32°N)
is derived by digitizing the depth contours and sounding depths less than 200
m from the hydrographic charts published by the National Hydrographic Office,
India. The digitized data are then gridded and used to modify the existing ETOPO5
and ETOPO2 data sets for depths less than 200 m. In combining the digitized
data with the original ETOPO data set, we apply an appropriate blending technique
near the 200 m contour to ensure smooth merging of the data sets. Using the
modified ETOPO5, we demonstrate that the original ETOPO5 is indeed inaccurate
in depths of less than 200 m and has features that are not actually present
on the ocean bottom. Though the present version of ETOPO2 (ETOPO2v2) is a better
bathymetry compared to its earlier versions, there still are differences between
the ETOPO2v2 and the modified ETOPO2. We assess the improvements of these bathymetric
grids with the performance of existing models of tidal circulation and tsunami
propagation.
For more details, please refer to: Sindhu et al 2007, J. Earth Syst. Sci.: 116(3);2007;261-274. The paper provides a detailed description of the generation, evaluation and validation of the modified bathymetry datasets.
The datasets are provided in three formats : ASCII, NETCDF and BINARY. (Click here to download)
NOTE: All the depth values in the modified datasets are positive values and the land elevations values are set to zero. The depth values are given in meters.
We have also provided a code, in the directory global_bathymetry, which enables the user to combine the modified datasets (which is only for the Indian Ocean), with the global bathymetry. The code is made available both in C and Fortran languages.
Please acknowledge National Institute of Oceanography, Goa, India for making the data available. Also please cite the following paper if you use any of the modified datasets.
Sindhu B, Suresh I, Unnikrishnan A S, Bhatkar N V, Neetu S, Michael G S, J.
Earth Syst. Sci.: 116(3); 2007; 261-274.