International Mass Loading Service



Summary

The Earth as a whole responses to external forces as an elastic body. Putting additional mass on the Earth's surface causes crust deformation. Changes of loading mass result in variable displacements of Earth's surface. If not properly accounted such variations distort precise geodetic measurements. Periodic loading causes harmonic site position variations which are detected in analysis of VLBI observations and other space geodesy techniques.

Mass loading has four constituents: 1) changes of air mass that results in change of surface air pressure; 2) change in ocean level due to lunar and solar tides; 3) change of ocean level due to wind and atmospheric pressure; 4) change in soil moisture. These four loading are to be taken into account in processing space geodetic data when precision better 1 cm is required.

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Mass loading is a substantially non-local effect. It is not sufficient to know mass change in the point of interest. In order to compute mass loading displacements, the mass change over entire Earth should be known. Changes in pressure exerted by the atmosphere and the hydrosphere can be deduced from the output numerical weathers, numerical ocean models, and numerical hydrology models. Handling the outputs of numerical models is not an easy task: their size exceed 1 Tb/year. Handling the output and computing loading regularly on a timely fashion is a challenge.

The goal of the International Mass Loading Service is to ingest outputs of numerical models, compute 3D displacements caused by mass loading, and to disseminate the results for the entire geodetic community on a regular basis, continuously, and with low latencies. The service is provided free of charge, and no registration is required.

Loading 3D displacements are provided as a) time series for 884 space geodesy sites; b) at a regular 0.25° × 0.25° grid; and c) as an on-demand on-line Internet service.

Download

In total, there are 3797509 files to download from this site. To facilitate downloading loading displacements or Stokes gravity coefficients induced by geophysical fluids, the list of URLs for downloading can be generating by filling a web form:
  1. Downloading precomputed time series of displacements for 884 space geodesy sites. in EPHEDISP format. This form will generate a list URLs of individual files or a control file for wget. The series are updated within 1 hour of availability of new data.
  2. On-demand computation of loading displacements for the list of sites that a user supplies. After willing a web form, computation of mass loading displacements is performed on our server.
  3. Downloading precomputed loading time series at the 0.25°×0.25° regular grid in netCDF format. This form will generate a list URLs of individual files or a control file for wget. The series are updated within 1 hour of availability of new data.
  4. Downloading or plotting time series of loading integrals computed over the whole Earth, or over the ocean, or over the land.
  5. Downloading precomputed time series of Stokes coefficients of the contribution of geophysical fluids to the geopotential in AGRA format. This form will generate a list URLs of individual files or a control file for wget. The series are updated within 1 hour of availability of new data.

  1. Smart downloading of the Mass Loading Service products.
  2. Current latency of the Mass Loading Service.
Loading displacements were computed with software package MALO.

Explore individual loadings

  1. Atmosphere pressure loading caused by variations of the atmosphere pressure.
  2. Non-tidal ocean loading caused by water mass re-distribution for reasons others than tides.
  3. Land water storage mass loading caused variations of distribution of the water on land.
  4. Ocean tidal loading caused by water mass re-distribution due to ocean tides.
Time series of the contribution of geophysical fluids to the geopotential up to degree/order 64.

Mirror

A mirror of the International Mass Loading Service http://alt.massloading.net runs independently. If you cannot access the main server, please use the mirror server.

Mailing list

Mailing list for discussing issues related to the atmospheric pressure loading service and for posting messages about changes. Only subscribers can post messages to the list. The messages posted to the list are available for viewing to all from the mail archive.

In order to subscribe or un-subscribe, please fill a registration form.

Publications

  1. L. Petrov, The International Mass Loading Service, http://arxiv.org/abs/1503.00191.
  2. L. Petrov, J.-P. Boy, Study of the atmospheric pressure loading signal in VLBI observations, Journal of Geophysical Research, 10.1029/2003JB002500, Vol. 109, No. B03405, 2004. Full text in PDF (871Kb)

Bibliography

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Acknowledgment

This work was supported by NASA Earth Surface & Interior program, grant NNX12AQ29G.


This page was prepared by Leonid Petrov ()
Last update: 2016.02.26_20:05:45