This is a GGFC Operational Product. The data here are updated quarterly at a minimum.
The 3-dimensional displacements have been derived using the method originally outlined in van Dam and Wahr .
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.)
- GLDAS soil moisture and snow water equivalent is used
- The data are given monthly
For more information on the GLDAS mass model, the user is referred to http://disc.sci.gsfc.nasa.gov/hydrology/documentation.
PLEASE NOTE: Time series for any individual grid location contain a long-term trend. Users are advised to remove this trend from their data before interpreting the 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 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 imo=1,12 read(iunit,1001) chyr,cmo,cref 1001 format(a4,1x,a4,1x,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
|chyr||year in character format|
|cmo||mon in character format|
|cref||reference frame in character formatr|
|rlon||longitude of data point|
|rlat||latitude of data point|
You may use the program gldas_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.cws. 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 2013.
GLDAS derived monthly, global surface displacements at 2.5 x 2.5 degree spacing.
Data set accessed YYYY-MM-DD at http://geophy.uni.lu/hydrology-downloads/
For questions regarding this data set, please contact T. van Dam, tonie.vandamuni.lu