ADIABATIC CHANGES OF MOIST AIR NEUHOFF 449 



Instead of the temperature term we have another in this equa- 

 tion, namely, — 1.82 $ which contains the total quantity of 

 moisture £. At the end of this stage the quantity of vapor (x), 

 which is not Constant but increased, can be obtained from the 

 expression 



e 



X = £ — ; 

 P' 



The equation for the change in the quantity of vapor can also be 

 written directly, viz: 



log x + 15.80 * = log* + 13.98 x + 1.82 £ 



After all the water is frozen the snow stage begins. 



If at the beginning of the hail stage the partial atmospheric 

 pressure p' — 482.6 mm is equal to the barometric pressure p = 

 487. 2 mm diminished by the vapor pressure e = 4.6 mm , as in our 

 previous example, and if the quantity of moisture present is £ = 

 12.57 grams of which the vapor is x = 5.9 grams and the water is 

 y = 6.6, then we obtain from equation (10) for the final pressure at 

 the end of the hail stage the values p' = 47i.8 mm whence p = 

 476. 4 mm . 



At the end of the hail stage there is present x = 6.1 grams of 

 vapor and z — 6.4 grams of ice, while 0.2 gram of the water that 

 was originally present has been evaporated. 



The new volumes are V = 1.246 cbm. and v = 0.231 cbm. 



§6. SNOW STAGE 



The behavior of the mass of air during its further adiabatic 

 expansion is now similar to that which prevailed during the rain 

 stage. The only difference consists in the fact that in place of 

 the specific heat of water we introduce the specific heat of ice 

 c e = 0.5 and we also add the latent heat of liquefaction for ice 

 r e = 79.24 to the latent heat of evaporation (r) for water, so that 

 instead of r we have to substitute r + r e . 



In other respects the process is the same as before; as the air 

 ascends and cools a further condensation of aqueous vapor occurs 

 but now it condenses directly to snow. 



Therefore the differential equation of the adiabat of the snow 

 stage becomes 



- (c p + Zc e )dT + Td ( *(r + r e )J -ART ^•••(10) 



