1. John Braun and Chris Rocken
GPS Sensed Small Scale Water Vapor Variability in the Southern Great Plains
John Braun and Chris Rocken

2. Outline Network Overview SW Observations vs PW Observations Results
Network Location
Station Components and Operation
SW Observations vs PW Observations
Results
Tomography Simulations
Example 3-D Refractivity Field

3. Location of Network NOAA GPS network with ARM SGP Region
Location of L1 network around ARM SGP Central Facility

4. GPS Station Components
GPS antenna
Radio modem antenna
GPS receiver/radio modem
Solar Panel
Battery backup
Each station equipped with GPS receiver, radio modem, and power source.
No additional infrastructure required.

5. Station Pictures

6. Precipitable Water and Slant Water
SW can be estimated along single GPS ray paths
Simultaneous observations along ray paths
PW is essentially an average of SW (after they have been scaled to zenith)

7. Volume Display of Satellite Ray Paths
5 minutes of observations at 30 second epochs

8. Variation in PW across Network
PW deviation with respect to the total PW

9. Simulated Tomography Layers
Input Field
Tomography Estimate

10. Simulated Tomography
Tomography Estimate
Input Field

11. Preliminary Tomography Results
500 m layers
Lowest 500 m

12. Conclusions
Network of 24 GPS stations installed and continuously operating
Less than 10 days of data have been lost due to logistics
More than 15 months of observations analyzed
Preliminary tomography results are encouraging
more vertical resolution needed (combine GPS with other instruments)
Specific cases need to be investigated

13. This work was supported by
Acknowledgments
This work was supported by
DOE Atmospheric Radiation Measurement Program
and
NCAR Advanced Study Program