ADIABATIC CHANGES OF MOIST AIR — -NEUHOFF 



46S 



For (1 + x) kilograms of moist air where x is the quantity of 

 moisture we have for adiabatic expansion in the dry stage 



= (cl + xc'i) dT - A (1 +'x) vdp = C p dT - A (1 + x) vdp 



where we have put 



L-n — C n + X C n 



By combination of this equation with the formula (14) we obtain 

 as the adiabatic hypsometric formula 



dh = Cp -dT -= Cp ' + x c p dT = C,dT . . (16) 



(1 + x) A 



(1 + x) A 



According to this formula we may compute the differences of alti- 

 tude of dry as well as of moist air in the dry stage, without knowing 

 the pressure and temperature, but only the difference of tempera- 

 ture for the two levels. The coefficient C x is, however, variable 

 with the mixing ratio (x) for moist air, as is shown in the following 

 table D. It is only for small altitudes and for high temperatures 



Table D 



that larger quantities of moisture occur than are contained in this 

 table, and in such cases the point of saturation is generally attained 

 very soon. For high altitudes the mixing ratio amounts to only 

 0.00 1 or 0.003, ^at is to say, only 1 to 3 grams of aqueous vapor 

 are mixed with a kilogram of dry air, so that on the average C x = 

 101 meters or At can be adopted as being 0.990 C. per 100 meters 

 in the dry stage. 



For the condensation stage we have the adiabatic thermal equation 



= U + £c) dT + Td 



-ART 



dp' 

 7 



