Slide 1EGU 2005, Vienna, Austria, 24-29 April 2005Tuesday, 26 April 2005 M. Troller (1), E....

EGU 2005, Vienna, Austria, 24-29 April 2005 Tuesday, 26 April 2005

M. Troller (1), E. Brockmann (2), D. Ineichen (2), S. Lutz (1), A. Geiger (1), H.-G. Kahle (1)

(1) Institute of Geodesy and Photogrammetry, Swiss Federal Institute of Technology, Zuerich, Switzerland (2) Swiss Federal Office of Topography, Geodetic bases and permanent networks, Wabern, Switzerland

Determination of the 3D Water Vapor Distribution in the

Troposphere on a Continuous Basis Using GPS


Swiss AGNES-Network (operated by swisstopo)

30 AGNES stations

48 additional stations

AGNES height range:

400 m (FHBB) -

3‘600 m (JUJO)

AGNES stations

Other stations


GPS-tomography – Voxel model

3x6 mesh elements, open elements at the boundaries 15 levels between 0 and 8000 meters; 1 more level alof Hourly profiles


GPS-Tomography: Real Measurements and Pseudo-Measurements

GPS Double Difference Delays: )()(2 sp

sq

rp

rq

rspq ρρρρρ −−−=Δ

Main Measurements:

Further Measurements:

GPS Zenith Delays

• Inter-Voxel Constraints (C)

• Ground Meteorological Measurements (P)

• Time Constraints (T)

• Radiosondes (R)

Pseudo- Measurements:


Comparison of Refractivity Profiles

C: Inter-voxel constraintsP: Ground meteorlogical dataT: Time constraintsR: Radiosondes


Comparison of Refractivity Profiles

FALE

ZIMM

PAYEC: Inter-voxel constraintsP: Ground meteorlogical dataT: Time constraintsR: Radiosondes


Time Series of rms compared to aLMo

0

2

4

6

8

10

12

14

16

10 12 14 16 18 20 22 24

Day of October 2004

mean rms [ppm]

C

CP

CPT

CPTR



rms compared to aLMo of the different GPS stations

0

2

4

6

8

10

12

FHBBSTABLOMOEPFLGENEUZNANEUCKREULUZEPAYEETHZSCHAMARTFRICSTGAHUTTBOURZIMMHOHTPFANSTCXSARGFALESAANDAVOSANBSAMEANDEJUJO

mean rms [ppm]

C

CP

CPT

CPTR



Mean rms of the individual layers compared to aLMo

0

2000

4000

6000

8000

10000

12000

0 5 10 15 20 25 30 35

mean rms and its standard deviation [ppm]

height of the voxel layer [m]

C

CP

CPT

CPTR



Statistical rms of all profiles over the entire period

[ppm] (refractivity unit)

mean offset mean rms mean std.

AWATOS C -2.3 7.3 6.0

AWATOS CP 0.6 5.0 4.0

AWATOS CPT 0.3 4.8 3.8

AWATOS CPTR 0.6 4.7 3.7

• 29 stations

• 336 time periods

Mean of:9744 profiles in total C: Inter-voxel constraints

P: Ground meteorlogical dataT: Time constraintsR: Radiosondes


Conclusions

• GPS-Tomography has been successfully developed

• An application using the Swiss National GPS reference network AGNES was demonstrated, the software is running routinely at swisstopo

• Tomography is a promising method for regions with dense GPS network: all weather, high spatial and temporal resolution

• Compared with the aLMo/7 analysis, a consistent accuracy of about 1mm water vapor was reached (calculated over voxel elements)

• The method has the tendency to introduce too much smoothing in the vertical


Outlook – New field campaign

• Region with complex topography (400 - 4000 m)

• 20 GPS receivers• 1 week, early July 2005• Tomography solution:

6x6 profiles, 5km mesh• Radiosondes and aLMo/7

for validation – currently under way


Outlook – Further developments

• Incorporate additional sources of humidity information in tomography software– GPS occultation (transverse data)– Satellite aloft cloud cover (profiles in upper troposhere)– Cloud location (saturated regions)– Lidar and other

• Use aLMo short range forecast (3h) as first guess– Weight should be derived from error statistic

• Systematic verification within a longer period

• Ingest humidity profiles in aLMo– Tune structure functions

• Impact study with aLMo/2

Slide 1EGU 2005, Vienna, Austria, 24-29 April 2005Tuesday, 26 April 2005 M. Troller (1), E....

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