FKB/SONDE/M1 - RH values may be slightly overcorrected.

The desiccant in the GC25 ground check set began to lose efficiency at the beginning of 
this time period.  Prior to 9/11/2007 the radiosonde RH readings while in the GC25 (assumed 
RH=0%) were below 1%RH.  The RH readings began to exceed 1%RH on 9/11/2007 and increased 
more or less exponentially to 2.3% RH by the end of 9/18/2007.  The desiccant was 
changed on 9/19/2007 and the radiosonde RH values while in the GC25 again dropped within the 
acceptable limit (< 0.5%RH, in fact).

Because the value obtained from the radiosonde while in the GC25 is subtracted from the 
subsequent RH values as part of the ground check procedure, it is likely that soundings 
done late in this period may be biased low by no more than 2%RH.  The exact amount of the 
correction applied is included in the netCDF header of each file.

If a 2%RH error bothers you, extract the RH correction value from the netCDF file 

header and add that value to the RH measurements contained in the file.

• dp
• rh