B4-10 RELEASE AND RECORDER RECORD 
temperature and humidity and enter circled dots on the first level of the 
recorder record and label them T and RH as appropriate. 
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Figure B4- 1. Significant Level (Surface) 
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6.3 Significant Level Above the Surface. No significant level will be 
placed within 10 mb of the surface level since this portion of the record 
may not be representative. 
6.4 Priorities for Selection of Significant Levels. In selecting signifi- 
cant levels, the temperature departure levels are selected first, addi- 
tional levels required by JB4-6.6 second, and relative humidity levels 
last. When selecting levels for temperature, however, the observer 
should be aware of the relative humidity trends so that, when necessary, 
a level may be selected advantageously to reflect changes in trend of 
both temperature and relative humidity. When the levels have been se- 
lected and the evaluated data plotted on the adiabatic chart, the resulting 
curves must closely reflect the profile of the recorded traces and agree 
everywhere with the traces within + 1°C from the surface up toand in- 
cluding 100 mb and+2°C from 99 mb up to and including the termination, 
and within 10% in relative humidity for all humidity evaluated. 
6.5 Selecting Significant Temperature Levels. In selecting levels for 
temperature, all points at which there is change in the slope ofthe traces 
on the recorder record must be examined for possible placement of 
significant levels. Find these points by using a straight-edge to identify 
successive segments having a uniform slope. 
a. Align the lower portion ofastraight-edge with the point where 
the recorded trace intersects the preceding significant level. 
If the preceding significant level is the surface, align the 
straight-edge with the ordinate equivalent of the observed 
surface temperature. 
Is (Og) FMH#3 
