1. Problems and measuring errors of radiosonde humidity measurements in the global aerological network and new possibilities of their correction and validation Ulrich Leiterer and Horst Dier, Meteorological Observatory Lindenberg, German Weather Service, Lindenberg, GERMANY

2. Content I. Overall view of the global aerological network II. The method of „standardized frequencies“ FN and comparison with uncorrected RS80-A-Humicap humidity data III.Correction steps for routine RS80 humidity measurements IV. Validation V. Results from the troposphere VI. Results from the stratosphere

3. I. Overall view of the global aerological network Radiosonde types and –stations which contribute with high availability (>= 67 %) for the data assimilation. ECMWF Data Coverage (All obs) - TEMP Differences in relative humidity (RH) measurements in the global radiosonde network Confirmation of the differences between several radiosonde types

4. Radiosonde types and –stations which contribute with high availability (>= 67 %) for the data assimilation. Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20032ulrich.leiterer@dwd.de

5. ECMWF Data Coverage (All obs) - TEMP Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20033ulrich.leiterer@dwd.de

6. Differences in relative humidity (RH) measurements in the global radiosonde network Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20034ulrich.leiterer@dwd.de

7. Confirmation of the differences between several radiosonde types Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20035ulrich.leiterer@dwd.de

8. II. The method of „standardized frequencies“ FN and comparison with uncorrected RS80-A-Humicap humidity data RS 90 Sensor Unit The Fn method Standardized Frequencies Fn calibration matrix Comparison with uncorrected RS80 routine data

9. RS 90 Sensor Unit Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20036ulrich.leiterer@dwd.de

10. The Fn method Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20037ulrich.leiterer@dwd.de

11. Standardized Frequencies Fn calibration matrix Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20038ulrich.leiterer@dwd.de

12. Comparison with uncorrected RS80 routine data Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 20039ulrich.leiterer@dwd.de

13. III. Correction steps for routine RS80 humidity measurements weather screen/groundcheck (100 % RH) - correction of RS80-A- radiosonde Temperature dependent correction function  2Uw(t) for RS80-A-humicap rel. humidity (water) on ice saturation Detection of sensor icing a) Example for an icing case Detection of sensor icing b) the climatologic treshold as criterion for icing Frequency of sensor icing

14. weather screen/groundcheck (100 % RH) - correction of RS80-A-radiosonde Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200310ulrich.leiterer@dwd.de

15. Temperature dependent correction function  2 U w (t) for RS80-A-humicap rel. humidity (water) on ice saturation Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200311ulrich.leiterer@dwd.de

16. Detection of sensor icing a) Example for an icing case Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200312ulrich.leiterer@dwd.de

17. Detection of sensor icing b) the climatologic treshold as criterion for icing Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200313ulrich.leiterer@dwd.de

18. Frequency of sensor icing Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200314ulrich.leiterer@dwd.de

19. IV. Validation Example for Ceilometer backscattering signal if the relative humidity is slightly below ice saturation Relative humidity profiles of the corrected RS80 routine sonde and two experimental sondes (FN Method), simultaneous ascent Relative humidity profiles of the corrected RS80 routine sonde and two experimental sondes (FN Method), simultaneous ascent (detail) Example of corrected RS80 A Humicap profile in cirrus clouds Comparison of RS80-A-Humicap with MOZAIC-Aircraft humidity sensor relative humidity comparison RS80 orig., RS80 corr., RS92, RS90 orig., RS90-reference Example for the precision of measurements of temperature and relative humidity in the simulation chamber : FN calibration matrix on the basis of several measuring methods

20. Example for Ceilometer backscattering signal if the relative humidity is slightly below ice saturation Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200315ulrich.leiterer@dwd.de

21. Relative humidity profiles of the corrected RS80 routine sonde and two experimental sondes (FN Method), simultaneous ascent Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200316ulrich.leiterer@dwd.de The relative humidity is in cirrus level at 9 km (no backscattering) near 5% RH below ice saturation.

22. Relative humidity profiles of the corrected RS80 routine sonde and two experimental sondes (FN Method), simultaneous ascent (detail) Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200317ulrich.leiterer@dwd.de

23. Example of corrected RS80 A Humicap profile in cirrus clouds Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200318ulrich.leiterer@dwd.de

24. Comparison of RS80-A-Humicap with MOZAIC-Aircraft humidity sensor Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200319ulrich.leiterer@dwd.de

25. relative humidity comparison RS80 orig., RS80 corr., RS92, RS90 orig., RS90-reference Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200320ulrich.leiterer@dwd.de Lindenberg, 06.03.2003 12:00 UTC

26. Example for the precision of measurements of temperature and relative humidity in the simulation chamber : Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200321ulrich.leiterer@dwd.de Basis for temperature : PTB gas calibration, basis for humidity : FN method

27. FN calibration matrix on the basis of several measuring methods Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200322ulrich.leiterer@dwd.de

28. V. Results from the troposphere homogenized time series of the rel. humidity U [%] above Lindenberg Frequency of the occurence of ice supersaturation (ISS) classes corrected radiosonde (RSA), microwave profiler (MWP) and GPS water vapor column (cmppw) comparison Examples for the incorrect relative humidity measurements in the stratosphere by different radiosondes Example for water vapor mixing ratio measurement in the stratosphere by FN-method; the same date as in Figure 26

29. homogenized time series of the rel. humidity U [%] above Lindenberg Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200323ulrich.leiterer@dwd.de

30. Frequency of the occurence of ice supersaturation (ISS) classes Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200324ulrich.leiterer@dwd.de

31. corrected radiosonde (RSA), microwave profiler (MWP) and GPS water vapor column (cmppw) comparison Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200325ulrich.leiterer@dwd.de

32. Examples for the incorrect relative humidity measurements in the stratosphere by different radiosondes Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200326ulrich.leiterer@dwd.de RS80origuncorrected (calibration issue 1988), RS92calibration issue (March 2003), RS80corrcorrected by FN-method RS90 FNFN-method (reference humidity profile) RS90 (Vaisala) the same sensor as used for FN-method, but with Vaisala calibration issue September 2003

33. Example for water vapor mixing ratio measurement in the stratosphere by FN-method; the same date as in Figure 26 Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200327ulrich.leiterer@dwd.de

34. VI. Results from the stratosphere Time series of water vapour content results from reference sonde ascents (FN-method) in the period June 1999 – April 2003 Mean vertical profiles of water vapour mixing ratio. FN-Method 99-01; 99-03; HALOE 92-99 Seasonal course of water vapour mixing ratio over Lindenberg from FN data in the period 1999 – 2003 (4 years) Seasonal course of water vapour mixing ratio over Boulder, Co from NOAA frost point hygrometer data (Vömel and Oltmans) in the period 1979 – 2003 (24 years)

35. Time series of water vapour content results from reference sonde ascents (FN-method) in the period June 1999 – April 2003 Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200328ulrich.leiterer@dwd.de

36. Mean vertical profiles of water vapour mixing ratio. FN-Method 99-01; 99-03; HALOE 92-99 Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200329ulrich.leiterer@dwd.de

37. Seasonal course of water vapour mixing ratio over Lindenberg from FN data in the period 1999 – 2003 (4 years) Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200330ulrich.leiterer@dwd.de

38. Seasonal course of water vapour mixing ratio over Boulder, Co from NOAA frost point hygrometer data (Vömel and Oltmans) in the period 1979 – 2003 (24 years) Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory email: ulrich.leiterer@dwd.de September 200331ulrich.leiterer@dwd.de