ABOUT_DRIFTERS Global surface drifter dataset from the Global Drifter Program. _______________________________________________________________________ _______________________________________________________________________ DRIFTERS.MAT and DRIFTERS.NC contain the global surface drifter dataset from NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML) Global Drifter Program (GDP) Drifter Data Assembly Center, online at http://www.aoml.noaa.gov/phod/dac/index.php This is essentially just a reorganized version of the AOML dataset. The only substantial difference is that the data is interpolated to a uniform six-hourly time grid with no gaps in the time index. All data values during gaps greater than 6 hours are flagged with values of INF. DRIFTERS.MAT is a Matlab version, and DRIFTERS.NC is a NetCDF version. DRIFTERS is distributed as a part of JDATA, a supplement to the software toolbox JLAB, and is available at http://www.jmlilly.net. _______________________________________________________________________ Matlab version LOAD DRIFTERS loads the structure DRIFTERS, with the following fields: drifters.about Pointer to this document drifters.id Drifter ids [24928 x 1 array] drifters.buoy Drifter buoy type [24928 x 1 array] drifters.num Date in DATENUM format {24928 x 1 cell} drifters.lat Latitudes {24928 x 1 cell} drifters.lon Longitudes {24928 x 1 cell} drifters.u Eastward velocity in cm/s {24928 x 1 cell} drifters.v Northward velocity in cm/s {24928 x 1 cell} drifters.t Temperature in centigrade {24928 x 1 cell} drifters.drogue Drogue presence flag {24928 x 1 cell} drifters.laterr Estimated latitude error {24928 x 1 cell} drifters.lonerr Estimated longitude error {24928 x 1 cell} drifters.terr Estimated temperature error {24928 x 1 cell} NUM, LAT, LON, U, V, T, and DROGUE are all cell arrays, with one drifter per cell. BUOY and DROGUE are metadata information described below. LATERR, LONERR, and TERR are error estimates from the original files. A number of routines are available in JLAB to work directly with such cell arrays, see JCELL. In particular, CELLPLOT will plot such data. After 'load drifters', type 'use drifters' to map the structure fields into named variables in the workspace--id, num, lat, lon, etc. To plot the entire drifter dataset, as in the above figure, type load drifters, use drifters, cellplot(380,lon,lat), topoplot where 380 specifies the right-hand axis of the plot, chosen to be the longitude of the southern tip of Africa. To convert the cell arrays into one long column vector, with a NAN separating each drifter, type 'cell2col(num,lat,lon,u,v,t);'. __________________________________________________________________ Metadata The fields BUOY and DROGUE give metadata information. BUOY is the drifter design type according to the following code: 1=SVP, 2=SVPB, 3=SVPC, 4=SVPBS, 5=SVPW, 6=SVPBW. DROGUE is true when the drifter's drogue is estimated to be present, and false otherwise. _______________________________________________________________________ NetCDF version The NetCDF version is basically the same as the mat-file version, but having all the cell array fields stored as column arrays with separating NaNs, see COL2CELL. Use the JLAB routine NCLOAD to load the NetCDF file and convert all the NaN-separated columns into cells, i.e. 'ncload drifters'. __________________________________________________________________ Dataset creation The files on which DRIFTERS is based are available for download at http://www.aoml.noaa.gov/envids/gld/FtpInterpolatedInstructions.php For completeness, the m-file ABOUT_DRIFTERS also contains the processing steps used in the creation of DRIFTERS.MAT and DRIFTERS.NC. If you wish to do this yourself, with JLAB on your search path, 'about_drifters --create' will recreate DRIFTERS.MAT and DRIFTERS.NC by reading in the original downloaded data. This will take a while. As of January 2020, the AOML drifter dataset consists of eight files: buoydata_1_5000.dat buoydata_5001_10000.dat buoydata_10001_15000.dat buoydata_15001_jun19.dat dirfl_1_5000.dat dirfl_5001_10000.dat dirfl_10001_15000.dat dirfl_15001_jun19.dat You'll need to make sure to put the directory containing the files on your Matlab search path using ADDPATH, e.g. 'addpath ~/Data/aoml'. __________________________________________________________________ See also JDATA, ABOUT_FLOATS. 'about_drifters --f' generates the sample figure shown above. Usage: about_drifters about_drifters --create __________________________________________________________________ This is part of JLAB --- type 'help jlab' for more information (C) 2007--2020 J.M. Lilly --- type 'help jlab_license' for details