ADIABATIC CHANGES OF MOIST AIR — -NEUHOFF 



479 



the two by preference. The small error of i per cent in the total 

 altitude will therefore be considered negligible. 



Such a table of adiabats and altitudes constructed on a large 

 scale enables us to solve in the most convenient manner the most 

 important questions as to the altitudes at which certain atmos- 

 pheric conditions occur under adiabatic expansion and as to the 

 conditions that must be present at certain altitudes. 



§ 12. THE ADIABATIC DIAGRAM 



The adiabatic diagram facing page 494 is a very practical form for 

 most problems. The basis of this diagram is a square network and 

 the units of length are i° for temperature, and 100 meters for differ- 

 ence of altitude. The diagram covers a range of temperatures from 

 + 30 to — 30 C. and of altitudes from o to 7000 meters. In 

 order to explain its construction more conveniently the following 

 fig. (8) is introduced which allows the individual items to be more 

 easily perceived. 



According to equation (15) the adiabats of the dry stage are 

 straight lines and exact diagonals if we put C = 100. If C = 101 

 then there is a slight departure therefrom. Ordinarily, however, 

 this difference can be neglected 

 and we can assume that the adia- 

 bats are, or run parallel to, the 

 diagonals of the respective small 

 squares. 



The diagram (see fig. 8) contains 

 diagonal lines only for each io° to 

 io°, since the interpolation for 

 other values is very easy. 



The adiabats of the condensa- 

 tion stage are constructed point 

 by point with the proper temper- 

 atures and altitudes. 



The curves are drawn at distances of every 2 of temperature, so 

 that on the one hand the appearance of the diagram is not confused 

 and on the other hand interpolations are not made too difficult. 

 Every fifth curve is emphasized by heavy lines. For the more con- 

 venient distinction of the adiabats of the condensation stage from 

 the adiabats of the dry stage, which are drawn across the diagram, 

 the first mentioned are indicated by dot and dash curves. 



On the isotherm of o° there is shown a small bend or nick in the 



-30° -20° -JO" 0° /0° 20° 30° 



FIG. 8. DIAGRAM OF ADIABATS 



