1. Intercomparisons of Water Vapor Measurements during IHOP_2002 – Radiosonde and Dropsonde Junhong (June) Wang NCAR Atmospheric Technology Division Acknowledgement: Kate Beierle, Scot Loeher, ARM EDC

2. Outline: 1.Goals for intercomparisons 2.Summary of Comparisons between Snow White and Vaisala RS80-H/VIZ-B2 during IHOP_2002 3.Comparison of Radiosonde Data at Norman, OK and ARM-B6 site (Purcell, OK) from 1996-2002 4.Comparison of dropsonde and radiosonde data during IHOP_2002

3. Errors in Observation system: 1.Natural Error: Instrument error (systematic and radom) Error of representativeness 2.Gross Error: Improperly calibrated instruments Incorrect registration of observations Incorrect coding of observations Telecommunication errors Goals: Mean errors/biases for the climate community Observation error variances (only instrument error) for the data assimilation community

4. Summary ±5%: Typical accuracy Requirements for synoptic meteorology Wang et al. (2003 ) http://www.atd.ucar.edu/homes/junhong/paper/Refsonde-GRL.pdf

5. Two sites are ~16 miles (25 km) apart. VIZ-B, VIZ-B2, Vaisala RS80-H, Vaisala RS90 were used at two sites during 1996-2002. 490 pairs of soundings launched within half hour and sampling the same air mass are found for comparisons. Comparisons of radiosonde data at Norman, OK and ARM-B6 site (Purcell, OK) from 1996 to 2002

6. VIZ-B/RS80-H B2/RS80H RS80-H/RS80-H RS80-H/RS90 (97) (131) (158) (104)

7. RH

8. Norman ARM-B6 Monthly Mean RH Profiles

9. T

10. Significance of T differences

11. Estimation of Instrument Error Variances Richner and Philips (1982) “The Radiosonde Intercomparison SONDEX”

12. Estimation of Instrument Error Variances

13. CAMEX-3 CAMEX-4 From Kooi et al. (2002) % MR difference between LASE and dropsonde RH dry bias from pervious studies From Vance et al. (2002) RD93-TWC RD93-RS90 ~8%

14. Comparisons of dropsonde and radiosonde data: RH Homestead (RS80-H 7) ARM-CF (RS90 2)

15. Comparisons at 18:04 UTC on June 9 Q T RH

16. Performance in Clouds (Dycoms-II) Marine Stratus Cumulus clouds

17. Time lag error Time-lag Error

18. Conclusions 1.The Sippican (VIZ) carbon hygristor used in 14% of global radiosonde stations fails to respond to humidity changes in the UT, sometimes even in the middle troposphere. This lack of response has produced significant and artificial humidity changes in the UT when the transition occurred and resulted in incapability of carbon hygristor to measure vertical and seasonal variations of humidity in UT. 2. Vaisala RS80-H Humicap used in ~51% of global radiosonde stations agrees very well with the SW in the middle and lower troposphere, but has dry biases in the UT. 3.Comparisons of seven years of data from two neighboring stations (Norman and ARM-B6) show unexplained significant and consistent drier RS90 than RS80-H (~5%) in UT and warmer temperature (~0.5  C) in the middle and upper troposphere at ARM-B6 than at Norman when Vaisala sondes were launched at both sites. 4.The dry bias in dropsonde humidity data found by previous studies are preliminarily evaluated by comparing with co-located radiosonde data during IHOP. The comparison shows good agreements except inside moist layers.

19. Comparisons between VIZ and RS80-H No response

20. Descending region Ascending region Descending region Matching dropsonde with C-130 ascending/descending profile

22. Height and Temperature at No-Response Level

23. Comparisons between RS80-H and RS80-H/RS90 RS90 (B6) v.s. RS80H (Norman) during IHOP (N=52) RS80H (B6) v.s. RS80H (Norman) 1999/2000 (N=158)

24. Significant and consistent drier RS90 than RS80-H in UT Significant and consistent warmer temperature in the middle and upper troposphere at ARM-B6 than at Norman when Vaisala sondes were launched at both sites.

25. Comparisons of dropsonde and radiosonde data: RH Homestead (RS80-H 7) ARM-CF (RS90 2)