IBAS) PREPARATIONS FOR SOUNDING 
(WB, N) Do not change the humidity controlling agent just before the 
baseline-check as several hours are required for conditions within the 
box to stabilize. 
(AF) Change the solution just prior to placing the radiosonde into the 
baseline-check set. 
5.3 The Baseline-Check Recorder Traces. The radiosonde is auto- 
matically or manually switched through the cycles of reference, temper- 
ature, and relative humidity. When the baseline-check cycle includes 
both the high and low reference, the order of switching is as follows: 
low reference, temperature, high reference and relative humidity. When 
the temperature and relative humidity traces are recording near the 
same ordinate value, the observer must remember thatthe temperature 
trace follows the low reference trace. An invalid flight would result if 
the ordinate readings were interchanged. When the baseline-check cycle 
has no high reference, the order of switching is as follows: low refer- 
ence, temperature, low reference, relative humidity. When the temper- 
ature and relative humidity traces are recording near the same ordinate 
value, the observer must be careful not to interchange the ordinate read- 
ings. When the traces cannot be definitely identified the following method 
must be used: 
a. take a valid baseline-check as defined in the following para- 
graphs, mark the level where a valid baseline-check was 
completed 
b. continue to record the switching of the radiosonde 
c. take the psychrometric reading 
d. open the door of the baseline-check box 
e. while the recorder is still recording the switching, change the 
relative humidity by blowing near the hygristor; an indication 
of rising relative humidity will now be recorded. In this way 
the relative humidity trace will definitely be identified 
f. count back to the level where a valid baseline-check was com- 
pleted and identify the relative humidity and temperature 
traces. 
Since the traces could not be identified originally the criteria in JB2- 
5.3.4 need not be complied with. A note will be placed on the recorder 
record, above the baseline-check, stating that the continued switching 
was necessary to identify the recorder traces. 
io h=@g) FMH#3 
