air pressure loading

http://holt.oso.chalmers.se/hgs/apload.html

HGS Air Pressure Loading

Here you can obtain time-series of surface displacement due to atmospheric pressure loading. The data come as 6 h samples of 3D local surface displacement (Vertical, East, North). Method is explicit convolution using Farrell's elastic Green's function on a spherical earth. Computation on a 1x1 degree grid with refinement 10 times at distances below 10 degrees. The air pressure load is derived from ECMWF surface pressure fields. The oceanic areas that are deeper than 30 m are assumed to respond instantaneously as an inverted barometer. All other areas are loaded by the full air pressure effect.
The assumption in space geodesy concurrent with International Terrestrial Reference Systems is that there is no permanent pressure loading effect. Thus, the mean of the time series is to be subtracted before the ordinates are applied as corrections to estimated positions. This average does inevitably depend on your observation epochs. Approximative mean values of station displacement (derived from a four-year period) are available from this site as shown below.

In any case, the whole suite of files below is purely experimental.

We offer data for the following categories of stations:

Category	Techniques	Sites	Periods
A	GPS	Nordic GPS stations, European IGS + a few more global IGS	continuously after Aug 1993 1996 - 2005
B	VLBI	NASA R&D, Europe, NEOS	selected experiments 1993-1997
C	VLBI	NASA R&D, Europe, NEOS	selected experiments 1989-1993
D	VLBI	CORE networks	1997--
E	VLBI	CORE networks like D	EPHEDISP format
F	SLR	many sites	1993 thru 2005

The format for the time series is pretty obvious:

Example
.

#1   1996jan01:00   -.00226    .00126    .00075
#2   1996jan01:06   -.00218    .00145    .00070
#3   1996jan01:12   -.00129    .00129    .00089
#4   1996jan01:18   -.00158    .00146    .00088
#1   1996jan02:00   -.00153    .00136    .00084
#2   1996jan02:06   -.00193    .00140    .00067
#3   1996jan02:12   -.00130    .00109    .00085

#n   yyyymmmdd:hh      DR         DE        DN

.
DR, DE, DN = Radial, East, North displacement
units = metre
The consequent increase of dates in the file cannot be guaranteed. Samples might be repeated, in which case the latest appearance is to be used.

A sample plot is available for the site METS (Metsähovi, Finland)

The long-term average offset for each station (which is to be subtracted in order to obtain continuity with analyses that are uncorrected for air pressure loading ) is available here for each category: A | B | C | D

NEW: EPHEDISP

We also provide time series in EPHEDISP format,
at least in a format very close to EPHEDISP according to NASA/GSFC. They appear on a per-site scheme. We have added two record types, designated to demarkate gaps. An B-record

Example
.

B 1 50692 .0 1997.09.01-00:00:00 YLOW7296

B n MJD s yyyy.mm.dd-hh:mm:ss site

marks the start of a contiguous segment (also the very start of the series),
and an E-record correspondingly the end of a contiguous segment. The segments are numbered (n).

Example
.

E 1 50721 64800.0 1997.09.30-18:00:00 YLOW7296

E n MJD s yyyy.mm.dd-hh:mm:ss site

Maybe we have to add the relative epoch number somewhere on these records.

en=`awk -v ep=$ep -v dt=$ts '/^B/{print (($3+$4/86400)-ep)/dt}' $file`

where

ts=`awk '/^T sample/{print $3}' $file`
ep=`awk -v dt=$ts '/^T begin/{print ($3+$4/86400)/dt}' $file`

We just started with this business (Jan 16, 2003), so there'll be a time when there is information only for the pleasure of the viewer and the discomfort of the user. Your feedback will help to ease the pains.

Time series files

Category A. BIFROST GPS	`ARJE \| BORA \| BRUS \| HASS \| HERS \| JOEN \| JONK` `KARL \| KEVO \| KIRU \| KIVE \| KOSG \| LEKS \| LOVO` `MADR \| MART \| MATE \| METS \| NORR \| NYAL \| OLKI` `ONSA \| ONSB \| OSKA \| OSTE \| OULU \| OVER \| POTS` `REYK \| RIGA \| ROMU \| SAAR \| SKEL \| SUND \| SVEG` `TROM \| TUOR \| UMEA \| VAAS \| VANE \| VILH \| VIRO` `VISB \| WETB \|` `.More IGS sites in a one big tar Klick here for a site list`
Category B. VLBI 1993--1997	`CRIMEA \| DSS15 \| EFLSBERG \| FD-VLBA` `FORTLEZA \| GILCREEK \| KOKEE \| KP-VLBA` `LA-VLBA \| MADRID64 \| MATERA \| MEDICINA` `MK-VLBA \| NOTO \| NRAO85 \| NYALES20` `OHIGGINS \| ONSALA60 \| OV-VLBA \| PIETOWN` `SC-VLBA \| SESHAN25 \| WESTFORD \| WETTZELL` `YEBES \| YLOW7296.` `.`
Category C. VLBI 1989-1993	`ALGOPARK \| AZORES \| BR-VLBA \| CRIMEA` `DSS15 \| DSS45 \| DSS65 \| EFLSBERG` `FD-VLBA \| FORTLEZA \| GGAO7108 \| GILCREEK` `GOLDVENU \| GORF7102 \| HARTRAO \| HATCREEK` `HAYSTACK \| HN-VLBA \| HOBART26 \| HOFN` `HOHNBERG \| HRAS \| KARLBURG \| KASHIM34` `KASHIMA \| KAUAI \| KOKEE \| KP-VLBA` `LA-VLBA \| MARCUS \| MARPOINT \| MATERA` `MEDICINA \| MIZNAO10 \| MK-VLBA \| MOJAVE12` `MOJAVLBA \| NL-VLBA \| NOBEY \| NOTO` `NRAO20 \| NRAO85 \| NRAO85 \| NRAO` `NYALES20 \| OHIGGINS \| ONSALA60 \| OV-VLBA` `PENTICTN \| PIETOWN \| PLATTVIL \| RICHMOND` `SANTIA12 \| SC-VLBA \| SESHAN25 \| TOULOUSE` `TRYSILNO \| VLBA85 \| VLBA85 \| VNDNBERG` `WESTFORD \| WETTZELL \| YLOW7296.` `.`
Category D. CORE-VLBI 1997-- For this category we can also provide the station pressure series as interpolated from the meteorological fields - on request.	`ALGOPARK \| BR-VLBA \| CRIMEA \| EFLSBERG` `FD-VLBA \| FORTLEZA \| GGAO7108 \| GILCREEK` `HARTRAO \| HN-VLBA \| HOBART26 \| KASHIM34` `KASHIMA \| KOGANEI \| KOKEE \| KP-VLBA` `LA-VLBA \| MADRID64 \| MATERA \| MEDICINA` `METSHOVI` \| `MIURA \| MIZNAO10 \| MK-VLBA` `MOJAVLBA` \| `NL-VLBA \| NOTO \| NRAO20` `NYALES20\|` `OHIGGINS \| ONSALA60 \| OV-VLBA` `SC-VLBA \|` `SESHAN25 \| SVETLOE \| SYOWA` `TATEYAMA \| TIGOCONC \| TSUKUB32` `URUMQI \| VLBA85-3 \| WESTBRK0 \| WESTFORD` `WETTZELL \| YEBES \| YLOW7296`
Category F SLR 1993-2005 All in three + two tars. Here is the station file. (Yes, we have no non-ib loading files .)	Loading displacements relative to solid earth centre (19 Mb) Loading displacements relative to joint mass centre SE+ATM (19 Mb) Rigid earth translations in Radial East North at the stations (17 Mb) Loading displacements relative to joint mass centre SE+ATM assuming non-inverse barometer ocean response (19 Mb) Rigid earth translations in Radial East North at the stations assuming non-inverse barometer ocean response (17 Mb)

.bye