International Mass Loading Service: loading type

Loading time series for stations — Loadings are computed for all epochs in the specified date range for 1272 stations. The loading displacements for all stations are grouped in ascii files in EPHEDISP format, one file per epoch. The time step of loading displacements depends on the model: either 3 or 6 hours. The contribution of harmonic variations at diurnal, semi-diurnal, and if applicable ter-diurnal, quad-diurnal band was subtracted from the surface pressure before loading computation.

Loading time series at a regular grid — Loadings are computed for all epochs in the specified date range at 2′ × 2′ regular grid in netCDF format, one file per epoch. The time step of loading displacements depends on the model: either 3 or 6 hours. The contribution of harmonic variations at diurnal, semi-diurnal, and if applicable ter-diurnal, quad-diurnal band was subtracted from the surface pressure before loading computation.

Time series of loading expansion in B-spline basis — Loadings are computed for all epochs in the specified date range at 2′ × 2′ regular grid in HEB format, one file per epoch. The time step of loading displacements depends on the model: either 3 or 6 hours. The contribution of harmonic variations at diurnal, semi-diurnal, and if applicable ter-diurnal, quad-diurnal band was subtracted from the surface pressure before loading computation.
The two-dimensional B-splines of the 3rd degree are used. The file contains a 3D array over dimensions longitude, latitude, component. The first index runs in the range [-2,Nlon+2], the second runs in the range [-2,Nlat], and the third runs in the range [1,3], where Nlon=10800, and Nlat=5401. The original grid runs from 0° through 359°58′ over longitude and -90° through +90° over latitude. In order to avoid errors in interpolation near the 0° meridian, the original grid is augmented by two nodes over longitude: 0° through 360°02′.
The two-dimensional B-spline is computed at the extended sequence of knots that starts with index -2. The first three knots have multiplicity three, or using another language their arguments is equal. The B-spline is normalized over unity: ∑ B_i(x) = 1.0
The third dimension runs over the components of the displacement field: up, east, north.

Loading harmonic variations for stations — The output file contains the sine and cosine amplitudes contribution of harmonic variations for a number of frequencies at diurnal, semi-diurnal, and if applicable ter-diurnal, quad-diurnal band for 1272 stations. The harmonics variations in the surface pressure at these frequencies was subtracted from the surface pressure before loading computation. Loading harmonic variations for all stations, all frequencies are grouped in one file in HARPOS format.

B-spline expansion of mass loading harmonic variations — The output file contains a 4D array of 2D expansion of the the sine and cosine amplitudes of harmonic variations for a number of frequencies at diurnal, semi-diurnal, and if applicable ter-diurnal, quad-diurnal band for for the global loading.
The two-dimensional B-splines of the 3rd degree are used. The file contains a 4D array over dimensions longitude, latitude, displacement component, harmonic component. The first index runs in the range [-2,Nlon+2], the second runs in the range [-2,Nlat], and the third runs in the range [1,3], and the fourth runs over [1, 2Nfreq], where Nlon=10800, and Nlat=5401. The original grid runs from 0° through 359°58′ over longitude and -90° through +90° over latitude. The harmonics component is either the cosine or sine amplitude for a given frequency. In order to avoid errors in interpolation near the 0° meridian, the original grid is augmented by two nodes over longitude: 0° through 360°02′. The meaning and order of frequency components is described in the metadata parameter SDS_name.
The two-dimensional B-spline is computed at the extended sequence of knots that starts with index -2. The first three knots have multiplicity three, or using another language their arguments is equal. The B-spline is normalized over unity: ∑ B_i(x) = 1.0
The third dimension runs over the components of the displacement field: up, east, north.

Loading S1-variations for stations — The output file contains the sine and cosine amplitudes contribution of harmonic variation at the S₁ frequency (period exactly 24 hour) for 1272 stations. The S₁ variations in the surface pressure was subtracted from the surface pressure before loading computation. Loading S1 variations for all stations are grouped in one file in HARPOS format.

Time series of the integrated loading — The output file contains the loading displacements integrated over the Earth, one file per epoch. Four quantities are computed: 1) integrated loading over the entire Earth's surface; 2) integrated loading over the land; 3) integrated loading over the ocean; 4) integrated loading over the ocean within latitudes ± 66°. The integrals are computed using the loading at 2′ × 2′ regular grid. The integrated loadings are given in ascii format.

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