2. 2

3. Gaffen et al. (1995) 3

4. 4 Total delay = Ionosphere + dry + wet Meteorological data (Ps, Ts) & estimated Tm Dual-frequency GNSS mea.: GNSS Ephemeris Station position Timing Dual-frequency GNSS mea.: GNSS Ephemeris Station position Timing Forward model Geodetic Noise to Meteorological signals

5. 5 GNSSRadiosondeSatellite Availability all weatherDifficulty in thunderstorms IR: clear MW: ocean Temporal resolution High (5 min-2 hourly) 1-2/daily>12-hourly Temporal coverage <~20 years>50 years~30 years Spatial coverage ~1000 stations globe Accuracy High (< 3mm)Low, various, biasLow, depending on radiosonde Long-term stability StableSignificant temporal inhomogeneity Diurnal variation Climate extremes Diurnal variation Climate extremes Validations of other measurements Climate trends

6. 6

7. 7 Number of GNSS Satellites

8. How good are GNSS measurements? Orbit Accuracy of GPS Satellites: ~2 cm 19942012

9. Jan. 1995 to Dec. 2012 2 hourly (0100, 0300, …, 2300 UTC) 380 IGS, 169 SuomiNet, 1223 GEONET Accuracy: < 3 mm Ps, Tm, ZHD and ZWD also available http://dss.ucar.edu/datasets/ds721.1/ Wang et al. (2007) 9

10. 10

11. 11

12. 12 Radiosonde validation: Systematic errors 1.934.151.72S.D. 0.811.97-1.67median Goldbeater’s skinCarbon hygristorCapacitive Wang and Zhang (2008a)

13. 13 Temporal inhomogeneity of radiosonde PW data Wang and Zhang (2008) Miami, U.S.A Suwon-Shi, Korea Beijing, China carbon hygristor Goldbeater’s skin Carbon hygristor capacitive capacitive with cover Relative PW differences (% Radiosonde-GPS)

14. Diurnal Variations (Lindenberg) Radiosonde before corr. GNSS Vaisala RS92 14 Radiosonde after corr. ERA-InterimJapanese Reanalysis Wang et al. (2013)

15. The diurnal cycle is less than 5% of annual mean PW Larger magnitude in summer than in winter Peak around late afternoon to early evening An order of magnitude smaller than seasonal variation Globe S. H. N. H. 15

16. Mears et al. (2010) Mears et al. (2011) 16

17. El Nino La Nina Land Ocean Mears et al. (2012) 17

18. 18 Land: X Radiosonde; O GPSOcean: MWR satellites

19. 19

20. 20

21. 21 Clausius- Clapeyron

22. PLATTEVILLE (PLTC) Akronar pt (P044) ALTERNATE MASTER (AMC2) SA62

25. 25 Tropical Strom Fay, Aug 17-29, 2008 Fatalities: 13 dir./23 indirect $560 million Area affected: Puerto Rico, Dominican Republic, Haiti, Jamaica, Cuba, Bahamas, South Eastern US Fay Dumps Record-Breaking Rain; Flood Victims Warned Of Alligator Swimming In Streets Homeowners Forced To Use Canoes POSTED: August 20, 2008

27. 27 http://xenon.colorado.edu/spotlight/index.php?product=spotlight&station=sg05

28. Reflected GPS Signals http://xenon.colorado.edu/portal/

29. 2012 Anomaly NMRI: Vegetation Water ContentNDVI: photosynthesis NLDAS: precipitationPW: Water Vapor

30. http://xenon.colorado.edu/portal/index.php Soil Moisture Variability at Marshall, CO

31. 31 DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite)

32. 32

33. 33 http://www.eol.ucar.edu/homes/junhong/homepage.htm http://xenon.colorado.edu/portal/

34. Implementation Meeting for GCOS Reference Upper Air Network (GRUAN) Essential GPS Equipment GPS Receiver/AntennaGeodetic quality dual frequency carrier phase observations are needed for any GRUAN site. Surface Observations (pressure and temp.) Pressure accurate to <0.5 hPa to remove hydrostatic delay. A 0.5 hPa error in surface pressure ~0.2 mm error in PW. InternetData need to be provided to analysis center(s) in timely manner to ensure that are included in routine processing. Station MonumentationGPS antenna should be installed in a manner that conforms to IGS standards. Cost of StationA research quality site can be installed for approximately $10K US.