Pressure and geopotential altitude comparison between the SRS-400 and SRS-C34 radiosondes

In this report the transition of hypsometer pressure measurements on the analog SRS-400 radiosonde to GPS geopotential altitude measurements on the digital SRS-C34 radiosonde is analyzed. The introduction of the GPS on the Meteolabor SRS-C34 digitale radiosonde drastically improved the precision of determining the vertical position of Swiss radiosondes at Payerne. Nevertheless the results of this report show that the mean differences on pressure and geopotential altitude between the SRS-400 and the SRS-C34 are small and do not need to be corrected.