PREPARATIONS FOR SOUNDING B2-11 
the corrected values under ''Baseline-Check Readings" on WBAN-31A. 
The readings should be in degrees Celsius and will be entered in ink 
opposite the caption ''°C.'' When the baseline-check temperature is en- 
tered in degrees Fahrenheit, this value should also be entered in ink. 
The dry and wet bulb temperatures will always be entered on WBAN-31A 
first, i.e., as soon as the readings are taken and before the ordinate 
values are evaluated. Once these data have beenentered on WBAN-31A, 
no values will be erased. If corrections are necessary or if the chart is 
used for a second release, the new or correct value will be entered in 
red immediately above the incorrect value. The original entry will be 
lined out, in red pencil in a manner that will leave it legible. 
Tot Baseline-Check Box Relative Humidity. Values of baseline- check 
relative humidity data, derived from psychrometric data referred to in 
§B2-7, may be computed by means of a psychrometric calculator or 
tables if a psychrometric calculator is not available. 
a. The psychrometric calculator will be used inaccordance with 
appropriate instructions in the Federal Meteorological Hand- 
book No. 1 (Surface Observations) and instructions printed on 
the device. If it is necessary to convert the psychrometric 
readings in order to use the calculator, the original and con- 
verted values will be entered on WBAN-31A opposite the ap- 
propriate caption (°F., °C.). 
b. When a psychrometric calculator is not available, the relative- 
humidity data will be computed by means of Table 4, Radio- 
sonde Observation Computation Tables (WBAN), using as 
arguments the temperature of the psychrometer dry bulb and 
the depression of the wet bulb in degrees and tenths Celsius. 
Interpolate as necessary. 
ec. The relative humidity, derived by either method will be en- 
tered to whole percent on WBAN-31A under the caption ''Base- 
line Check Readings, Water." 
8. Evaluation of Baseline-Check Data. Throughout this manual, the 
term ordinate is used as equivalent to the terms ''Temperature Ordi- 
nate,'' "Chart Division,"' and ''Frequency Division" that are found on the 
various types of evaluators and calibration charts used. The left edge of 
the recorder trace will be used for all evaluations. Evaluators will be 
used to convert temperature and relative humidity ordinate values from 
the recorder record to temperature in degrees Celsius and relative hu- 
midity in percent. Care must be exercised that the evaluators used are 
appropriate for the thermistor and hygristor used. 
1-1-69 FMH#3 
