This page contains instructions to download global hourly location and velocities from the GDP surface drifters as described in Elipot et al. (2016), "A global surface drifter dataset at hourly resolution", J. Geophys. Res. Oceans,121 doi:10.1002/2016JC011716. This study reports the methods used to produce location and velocity estimates along the trajectories of GDP surface drifters, tracked by either Argos or by GPS.
Version 1.01, released 19 January 2017
Release notes for version 1.01:
The data are provided via anonymous ftp as ASCII files (compiled in a compressed tar file) and as NetCDF files.
The data from Argos-tracked drifters are in the files containing the acronym WMLE (Weighted Maximum Likelihood Estimation), referring to the interpolation method used for Argos fixes.For ASCII files, please refer to the accompanying README file.
The data from GPS-tracked drifters are in the files containing the acronym GPS. For ASCII files, please refer to the accompanying README file.
For the NetCDF files please refer to the metadata within these files.
Instructions for obtaining all files via ftp:
List of files:
driftertrajGPS_1.01.nc - All GPS-tracked drifters in NetCDF format
driftertrajWMLE_1.01.nc - All Argos-tracked drifters in NetCDF format
driftertrajGPS_1.01.tar.gz - All GPS-tracked drifters in ASCII format
driftertrajWMLE_1.01.tar.gz - All Argos-tracked drifters in ASCII format
README_driftertrajGPS_1.01.txt - Readme file for GPS-tracked ASCII files
README_driftertrajWMLE_1.01.txt - Readme file for Argos-tracked ASCII files
Or go directly to :
ftp://ftp.aoml.noaa.gov/pub/phod/buoydata/hourly_product and download the files you need.
Queries, questions, comments, and the reporting of issues with these products should be directed to Drs. Rick Lumpkin, Shane Elipot, or Renellys Perez. If you would like to receive notifications of updates to the hourly data set, email your request to Dr. Rick Lumpkin.
If you use this dataset in your studies and publications, please cite:
Elipot, S., R. Lumpkin, R. C. Perez, J. M. Lilly, J. J. Early, and A. M. Sykulski (2016), "A global surface drifter dataset at hourly resolution", J. Geophys. Res. Oceans, 121, doi:10.1002/2016JC011716.
Preliminary analyses of the drifter velocity variance showed that this dataset is a valuable new tool for the study of relatively small-scale and high-frequency, oceanic processes. In particular, velocity rotary spectra suggest that high frequency tidal and internal wave motions are detectable globally. Below is a figure adapted from Elipot et al. (2016) which illustrate that the new dataset exhibits more velocity variance compared to the 6-hourly velocity product.
Figure caption: (a) zonally averaged drifter rotary velocity spectra in 1 degree latitude bins from 2048-hour (~85 days) trajectory segments at 1-hour resolution, overlapping by 50 percent, from the new global hourly product. (b) same as in (a) but zoomed in for frequencies in the range +/- 3.2 cpd. The black dashed curve indicates the inertial frequency (-f/(2*pi) cpd) and the white dashed curve the Coriolis frequency (f/(2*pi) cpd). Note that the color scales indicate different ranges of values and are both saturated. (c) same as in (b) but calculated from the post-2005 6-hourly Kriged global product for the same trajectories.