B4-32 RELEASE AND RECORDER RECORD 
from a previous portion of the sounding, and, using this relationship at 
each high reference, determine a low-reference value. Draw the drift 
line through these points. If all reference contacts should become un- 
readable, but the temperature, relative-humidity, and hypsometer, if 
applicable, record continues readable, the drift line will be drawn verti- 
cally - that is, parallel to the printedordinate lines from the last read- 
able low (or high) reference contact to the termination of the sounding, 
provided that there has been little or no drifting and shifting and the 
temperature record indicates little possibility of a shift having oc- 
curred after the low (or high) reference contacts became unreadable. 
Under these circumstances, the data will be classified as accurate for 
20 contacts, doubtful for the next 20 contacts, and missing thereafter. 
However, if the record indicates that an appreciable amount of shifting or 
drifting occurred without low or high references being recorded, the data 
will be classified as missing, since the possible error in such cases may 
be appreciably large. 
11. Data at Significant Levels. 
11.1 Numbering of Levels Selected. Number each level, making the 
surface level number 1, (labeled SFC-1). Write the appropriate number 
upon the level at the extreme left of the recorder record. In case of 
multiple ascents (see JB4-6.6(a)), the same level number will be given 
to the base of the last ascent which is equal in pressure to the top of the 
first ascent. 
If it is necessary to place additional levels on the recorder record after 
the levels have been numbered, the additional levels may be numbered 
alphabetically as 1A, 2A, 2B, etc. 
11.2 Drift Correction. On all levels enter to the left of the drift line 
the ordinate difference to tenths between the drift line and the ninety- 
fifth ordinate. If the difference is zero, enter 0. Place a plus sign before 
the difference if the drift line is to the left of the ninety-fifth ordinate, 
and a minus sign if it is to the right. Omit this entry if a correction for 
low-reference drift has already been entered at this point, i.e., the level 
intersects the bottom or top of a low reference trace. 
11.3 Pressure-Contact Value. At each significant level, determine the 
pressure-contact value to the nearest one-tenth contact by counting the 
contacts from the preceding reference contact, numbered in accordance 
with JB4-9.1, to the given level. A contact begins at the base of the rela- 
tive humidity or reference portion andends at the top of the temperature 
portion. Except when turbulence is encountered, determine proportional 
parts of a contact with reference to the whole contact as it appears on 
1-1-69 FMH#3 
