ECCO Loading

THESE DATA ARE CURRENTLY BEING UPGRADED; DO NOT USE UNTIL FURTHER NOTICE (09-09-2014).

Here you will find global grids of loading derived from the ECCO (http://ecco.jpl.nasa.gov) ocean bottom pressure data set.

This is a GGFC Operational Product The data here are updated quarterly (every 3 months) consistent with updates from the ECCO consortium.

The 3-dimensional displacements have been derived using the method originally outlined in van Dam and Wahr [1987].

van Dam, T. and J. Wahr, 
Displacements of the Earth's surface due to atmospheric loading: 
Effects on Gravity and Baseline Measurements, 
J. Geophys. Res., 92, 1281-1286, 1987.)

Specifics include:

1. ECCO ocean bottom pressure used is currently from the kf080 analysis
2. The data are given every 12 hours at 06 and 18 hours

PLEASE NOTE: Time series for any individual grid location contain a long-term trend. The trend is primarily due to the fact that oceanic volume and not mass, is held constant in the ECCO ocean general circulation model. Users are advised to remove this trend from their data before interpreting the higher frequency results.

The data provided here are first organized by reference frame. Within each reference frame directory the data are organized by year, then by day. Each day file contains 2 epochs of data at the following epochs: 06, 18. Each individual file contains the global (2.5 deg. X 2.5 deg) 3-dimensional surface displacement (in mm) for the epoch corresponding to the file name.

Each file can be read using the following algorithm (or something equivalent) where dvt is surface displacement to the north, dvl is surface displacement to the east, and du is surface displacement in the radial direction:

     do ihr=1,2
        read(iunit,1001) chyr,cdoy,chhr(ihr),ref
1001    format(a4,1x,a3,1x,a2,1x,a2)
        do ilon=1,144
           rlon=(ilon-1)*2.5
           do ilat=1,73
              rlat=90.-(ilat-1)*2.5
              read(unit,1002) vt(ilon,ilat),vl(ilon,ilat),du(ilon,ilat) 
1002          format(3(f10.4,2x))
           end do
        end do
     end do

You may use the program ntol_tseries.f to extract the data for a single latitude and longitude.

The program will need to be adapted to your particular needs. However, before altering the program, please compile on your system and confirm that you obtain the results similar to those in stjo.ntol. Details are inserted as comments in the fortran file.

Anyone using this data set is requested to use the following citation:

van Dam, T., 2010, Updated October 2010. 
ECCO derived 12-hourly, global surface displacements at 2.5 x 2.5 degree spacing. 
Data set accessed YYYY-MM-DD at http://geophy.uni.lu/oceans-downloads/

For questions regarding this data set, please contact T. van Dam, tonie.vandamuni.lu