B2-10 PREPARATIONS FOR SOUNDING 
c. If the baseline-check is made manually the humidity traces 
must satisfy (a) or (b) above, except that when (b) is used 
the left edges of the three traces must fall on a straight line 
covering not more than 1.0 ordinate. 
0.3.3 Temperature. The temperature traces must satisfy one of the 
following conditions: 
a. Two consecutive temperature traces must be aligned so that 
a line connecting the upper left edge of each will be parallel 
to the ordinates printed on the recorder paper. 
b. If the baseline check is made manually (see JB2-13), two con- 
secutive temperature traces must be aligned in accordance 
with (a) above, or three consecutive temperature traces must 
show a trend in the same direction, either rising or falling 
and not cover more than 0.5 of anordinate. Whenever a trend 
is used, the left top edges ofthe traces must fall on a straight 
line, and the radiosonde indication that the temperature is 
changing must be verified by additional test thermometer 
readings. 
5.3.4 Termination of a Baseline-Check. When the requirements for a 
satisfactory baseline-check recording have been met, terminate the re- 
cording upon the completion of the low reference following the last good 
humidity trace. The low reference must be unadjusted and the left edge 
of the trace recording at 95.0 ordinates. 
6. Conservation of Recorder Paper. Continue the receiving and re- 
cording units in operation, but turn off the recorder paper-drive mech- 
anism when it is expected that more thanten minutes will elapse before 
the release of the balloon. The paper-drive mechanism will be turned on 
again before releasing the balloon. 
7. Baseline- Check Psychrometric Readings. Immediately after plac- 
ing the radiosonde in the baseline-check box, wet the muslin on the wet 
bulb. (While wetting the muslin check to seeif it is becoming dirty; if it 
is, replace the muslin before the next baseline-check). If the baseline 
check is not completed within five minutes, rewet the muslin of the wet 
bulb two to three minutes before readings are to be taken. Make the 
readings at the time of maximum depression ofthe wet bulb, which usu- 
ally occurs about two to three minutes after wetting the muslin. Read the 
dry and wet bulb temperatures to the nearest0.1 degree. If necessary, 
apply the thermometer corrections to the readings in accordance with 
Federal Meteorological Handbook No. 1 (Surface Observations) and enter 
ie teal ods) FMH#3 
