Changes:

1. 2005.10.30 Computed and made available displacements caused by the atmospheric pressure loading at the 2.5x2.5 deg grid from 1976.01.01 through 1989.01.01. Thus the series of displacements on the grid for 30 years became available.
2. 2005.10.23 Computed displacements for 1224 GEONET (Japanese GPS network) sites from 1992.01.01 through 2005.10.14_18:00 and put them in both http://gemini.gsfc.nasa.gov/aplo and http://lacerta.gsfc.nasa.gov/aplo_geonet
3. 2005.08.22 Computed and made available displacements caused by the atmospheric pressure loading at the 2.5x2.5 deg grid from 1989.01.01 through now. Displacements at the 2.5x2.5 deg grid are now updated nightly.
4. 2005.07.12 Changed over to displacements with respect to the center of mass of the total Earth, the solid Earth and atmosphere.
5. 2005.05.13 Atmospheric pressure loading caused by S1, S2 variations of the atmospheric pressure has been recomputed. First, an errors in re-gridded Ponte-Ray original file from 1.125x1.125 degree grid to 2.5x2.5 and 1.0x1.0 degree field has been fixed. Second Green's functions were changed. The new Green's function is used for computation of displacements with respect to the center of mass of the total Earth: the solid Earth and the atmosphere. Before 2005.05.13 displacements with respect to the total Earth were computed.

   Several sets of coefficients was computed:

   • For the case when the inverted hypothesis was invoked;
   • For the case when the inverted hypothesis was not invoked;
   • For 619 sites;
   • For 1.0x1.0 degree grid.
   The amplitudes of displacements at the grid are provided in both HARDISP and netCDF format.
6. 2005.05.13 Numerous plots of gridded amplitudes and phases of the S1 and S2 atmospheric pressure variations, Up, East and North components of displacements caused by loading for both the IB and non-IB cases were posted at the atmospheric pressure loading Web page.
7. 2005.02.23 Several reorganizations:
   
   1. More stations were added: 132 DORIS stations and 30 DSN antennas used for tracking interplanetary spacecrafts.
   2. Complete series from 1976.01.01 to 2005.02.19 regardless of station begin/end time are be computed. The prefix of the series is vsgd_
   3. Three compressed tar.bz2 for the time series in ascii EPHEDISP format are generated:
      • from 1976.01.01 till 31-DEC 18:00 of the previous year; aplo_py_eph.tar.bz2 This file is updated annually.
      
      
      • from 01-JAN 00:00 of current year till the last available epoch: aplo_ty_eph.tar.bz2. This file is updated annually.
      
      
      • from 01-st day of the previous month till the last epoch. The first file will be updated daily, the last two files will be updated daily. aplo_2m_eph.tar.bz2
      
      

8. 2005.01.24 The experimental series of the Stokes coefficients of the atmospheric contribution to the geopotential has been computed. The service of daily update of this series has been established.
9. 2004.09.24. The atmospheric pressure loading service on HP computer was shutdown.
10. 2004.08.31
    1. Renamed (old) aplo.shtml to aplo_old.shtml . Renamed aplo_new.shtml to aplo.shtml .
    2. Added computation of latency
    3. Activated list_loading@gemini.gsfc.nasa.gov
    4. Added an example of a routine for smart downloading the time series.
11. 2004.07.22 Prepared new Web page http://gemini.gsfc.nasa.gov/aplo/aplo_new.shtml and new operational series which will be running in parallel with the old series for 1-2 months. Changes in new series:
    1. 497 GPS stations are included in the list. In total, displacements for 560 sites are computed.
    2. Site names are changed. The previous scheme used IERS dome numbers. Several stations as far as 20 km apart were found with the same dome number which made using IERS Dome number as site identifier impossible. The new scheme uses 8-letter upper register IVS name for VLBI stations , 8-letter name for SLR station (first letter capital, all others are in lower register) for SLR stations, and 4-letter upper register IGS names of GPS stations.
    3. Displacements are computed on Pentium-4 Prescott computer. Therefore, binary files are little endian, while the old series were computed on HP and, therefore, were big endian.
    4. URLs of the new series are different from the old series.
    5. New auxiliary files were added:
       • update_date.txt -- Date of the last series update
       • loading_date.txt -- Date of the last loading epoch
       • history_date.txt -- History of updates
    6. Links to short and raw log-files are provided.
12. 2004.06.15 Fixed reanal_to_atm3 -- the previous version gave up in the case if geopotential height and surface pressure NCEP data files had different ending time epoch.
13. 2004.06.01 Computed atmospheric pressure loading for VLBI, SLR and GPS stations. In total, for 560 sites. New series did not replaced operational series.
14. 2003.05.21 Operational software for computation of the atmospheric pressure loading was upgraded and the displacements have been re-computed for all stations and epochs in 2004. This has eliminated previously detected wrong values of displacements for the epochs when pressure loading was missing.
15. 2003.05.18 Source code was modified in order to trace cases when NCEP does not provide surface pressure for specific dates and put fillers instead of pressure. The early version did not recognized this case and produced the wrong displacements. The current version recognizes it and insert in the output files interpolated or extrapolated values and generates the file of missing dates.

    Source code was significantly simplified and a standard unix installation was developed (./configure; make; make install)

    Code was tested under Linux, HP and Sun platforms. All tested Updated code is posted in aplo source code Web page.

16. 2003.07.19 It was realized that diurnal and semi-diurnal variations in surface pressure are not modeled properly in NCEP due to6 hour sampling. Procedure for computations of pressure loading was modified. Sine and cosine components of diurnal and semi-diurnal variations in surface pressure for each cell are computed over the period of 20 years and stored in a special file. During computing pressure loading contribution due to these variations is subtracted from the NCEP pressure field. Pressure loading due to atmospheric tides according to Ponte and Ray model (2002) is computed and stored in a special file.
17. 2003.05.31 SLR stations are added. Atmospheric pressure loading is computed not for stations, but for sites. Each site may have several stations, VLBI or SLR. New site naming scheme was adopted.
18. 2003.03.18 Public access to the atmospheric pressure loading service is announced. The paper is submitted to JGR.
19. 2002.12.12 Atmospheric pressure loading service established. Time series of the atmospheric pressure loading for VLBI stations for all epochs when the station was active are computed. Pressure loading is updated nightly.
20. 2002.10.30 Call for suggestions and comments of the data formats for atmospheric pressure loading.
21. 2002.07.11 Beginning of development.

This page was prepared by Leonid Petrov ()
Last update: 2005.10.30_07:08:35