PREPARATIONS FOR SOUNDING B2-15 
Figure B2-6. WB #500, Relative Humidity Evaluator 
10. Humidity Evaluator. Using the appropriate humidity evaluator, set 
the cursor over the humidity ordinate value. Rotate the humidity disk 
until the baseline humidity value foundon the family of curves lies under 
the cursor line and the baseline-check dry bulb reading. Lock the evalu- 
ator. For any humidity value, set the hair line on the cursor at the hu- 
midity-ordinate value and read the humidity to the nearest whole percent 
under the temperature value on the cursor, interpolating as necessary 
between the curved lines. 
10.1 Humidity Limits. If limits have been established for the humidity 
evaluator, they will be indicated by two markson the ordinate scale be- 
tween which a mark on the humidity scale must fall. If limits have not 
been established for the humidity evaluator in use, these marks will not 
be present and the evaluator will simply be adjusted to the baseline hu- 
midity readings. The hygristor will be rejected and another baseline- 
check taken with a new hygristor if the humidity is out of limits for the 
evaluator in use. Reject the radiosonde if the humidity of the second 
baseline-check is also out of limits. If a radiosonde that does not have 
its baseline-check humidity within limits is released, the humidity aloft 
will be considered missing and a second release may be required. (see 
J B4-8.3). 
11. WBAN-31 Entries. Under ''Baseline-Check Readings", enter in the 
indicated spaces the time of the baseline-check (GMT), temperature and 
relative humidity ordinate values, and the baseline-check temperature 
and relative humidity. The latter two entries will be made in ink (see 
§B2-7.) 
12, Unstable Baseline-Check. When an unstable record is received for 
any of the transmitted circuits, check the receiver tuning and the check 
1-1-69 FMH#3 
