INTRODUCTION 
Radiosonde observations, or 'RAOBS'' as they are termed, are made 
to determine the pressure, temperature, and humidity from the surface 
to the point where the balloon bursts. The radiosonde consists of meteor- 
ological measuring elements coupled toa radio transmitter and assembl- 
ed into a small lightweight box. The device is carried aloft by a balloon 
filled with hydrogen or helium gas. Included inthe train is a small para- 
chute to slow the descent of the instrument after the balloon bursts, 
thereby minimizing the danger of injury to life and property. As the 
balloon rises, measurements of pressure, temperature, and relative 
humidity are transmitted to a ground station where the data are record- 
ed automatically. An observer then transcribes the information into a 
more commonly used form andplots it onvarious charts. Measurements 
of pressure are made in millibars, temperature indegrees Celsius, and 
moisture in percent of relative humidity. The Celsius temperature scale 
is the same as the centigrade scale and replaces that scale in all meteor- 
ological observations. 
As the balloon rises, it is followed either visually by an observer ata 
theodolite, or electronically by radio-direction-finding equipment that 
tracks the transmitted signal. The balloon's drift away from the re- 
lease point is plotted, and from this the direction and speed of the air 
movements are determined. The winds-aloft observation is termed a 
"RABAL" when the tracking is done visually, and a ''RAWIN" when the 
tracking is done electronically. A combined rawin and raob is termed a 
"RAWINSONDE." Instructions for the rabalor rawin portionof the obser- 
vation are contained in the Federal Meteorological Handbook #5 (Winds- 
Aloft Observations). 
Raobs, rawins, and rawinsondes have many procedures incommon., This 
handbook deals primarily with those procedures necessary in taking the 
raob. While effort was made in writing this handbook to list the pro- 
cedures in the order that they would normally be performed, the 
various types of equipment in use willnecessitate some variations in the 
actual sequence of operation. Cross reference is made throughout the 
handbook and an index is placed at the end to facilitate the finding of 
specific instructions. Tables and illustrations integral with the text are 
given a double number to indicate the chapter in which they appear, e.g., 
Table B2-1 indicates the first table in chapter two of Part B, and Figure 
B4-3 indicates the third illustration in chapter four of Part B. 
1-1-69 Ms FMH#3 
