Humidity Measurement Improved Algorithm

  • ​Humidity measurement algorithm has been improved to take into account sensors response time and sensor's heating by solar radiation, latter indicated formerly as dry biased humidity readings at high altitudes.
  • The algorithms' biggest impact is in day time soundings at altitudes of approximately ten to fifteen kilometers depending on the humidity profile and tropopause height.
  • The new algorithm was used in the WMO Radiosonde Intercomparison, Yangjiang, China, July 2010.
  • Note! This new algorithm is applicable only for digital radiosonde RS92-SGP.
  • Instructions for simulating the old database files with the DigiCORA® software version 3.64 can be found in the following document: Improved calculations MW31 3.64
Effect on Integrated water vapour column example, tropical conditions
  • 17 day soundings and 18 night soundings included
  • Day soundings average with new algorithms is 59.3 kg/m2 and with old algorithms 57.4 kg/m2
  • Night soundings average with new algorithms is 60.4 kg/m2 and with old algorithms 60.4 kg/m2 
Sounding example, tropical conditions

Sounding example for solar radiation algorithm
Blue = relative humidity with solar radiation algorithm and response time algorithm
Grey = relative humidity without new algorithms
Day time sounding (tropical conditions)

Sounding example, high latitude conditions

Sounding example for solar radiation algorithm
Blue = relative humidity with solar radiation algorithm and response time algorithm
Grey = relative humidity without new algorithms
Day time sounding (high latitude conditions)

Sounding series statistics example, tropical conditions

Comparison result between new and old calculation. Statistics of day time flights in tropical conditions, 20 flights
Blue = relative humidity with solar radiation and response time algorithms
0 %RH reference line = relative humidity without new algorithms

Sounding series statistics example, high latitude conditions

Comparison result between new and old calculation. Statistics of day time flights in high latitude conditions, 50 flights
Blue = relative humidity with solar radiation and response time algorithms
0 %RH reference line = relative humidity without new algorithms

  • Flight reproducibility test verifies the agreement between similar types of radiosondes when measuring the same atmospheric conditions. Based on the test results the new SW-based corrections, when being effective, also maintain the high level of reproducibility characteristics of Vaisala RS92 Radiosonde humidity sensor.

Reproducibility in sounding























Twin sounding differences with standard deviations using new algorithms, high latitude conditions.
Left  = Day time, 25 flights
Right = Night time, 5 flights