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

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

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

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 September

ECMWF Data Coverage (All obs) - TEMP Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

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 September

Confirmation of the differences between several radiosonde types Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

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

RS 90 Sensor Unit Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

The Fn method Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

Standardized Frequencies Fn calibration matrix Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

Comparison with uncorrected RS80 routine data Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

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

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 September

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 September

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 September

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 September

Frequency of sensor icing Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

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

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 September

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 September The relative humidity is in cirrus level at 9 km (no backscattering) near 5% RH below ice saturation.

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 September

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 September

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 September

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 September Lindenberg, :00 UTC

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 September Basis for temperature : PTB gas calibration, basis for humidity : FN method

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 September

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

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 September

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 September

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 September

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 September 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

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 September

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 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)

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 September

Mean vertical profiles of water vapour mixing ratio. FN-Method 99-01; 99-03; HALOE Problems and measuring errors of radiosonde humidity measurements in the global aerological network DWD-Lindenberg Observatory September

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 September

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 September