328 TABLK 83 



LIFTING CONDENSATION LEVEL DATA 



Lifting condensation temperature.— If a parcel of air is lifted adiabatically to its 



condensation level with the potential temperature and the mixing ratio remaining 

 constant, 



_£_ = _£i£ I (1) 



r 7 T~ k 



k _io g e = -\og\e,c/Tc k ) 



or log 7*-log e = -\og\e,c/Tc k J (2) 



where 



T = initial temperature, °K., 



e = vapor pressure of the space at the initial temperature, 

 T e = temperature at the condensation level, °K., 

 e, e = saturation vapor pressure at the temperature of the condensation level, 



k = R/c P = 0.286. 



To find the lifting condensation temperature if the temperature and dew point at the 



l 



initial level are given, determine log T corresponding to the temperature (°C.) at the 

 initial level from part A of Table 83. In accordance with equation (2) subtract from this 

 the value of log e corresponding to the initial dew-point temperature (°C.) as determined 



from part B thus obtaining the difference, —log \e, e /T e */• Enter part C with this 

 difference as the tabular value. The corresponding argument is the condensation tem- 

 perature (°C). 



If the temperature and relative humidity at the initial level are given, (2) may be 

 rewritten 



log ( C//100) + log V e./T ~ k ) = log ( e.e/Tc * / (3) 



where U is the "approximate" relative humidity ' and e. is the saturation vapor pressure 

 at the initial temperature. To obtain the lifting condensation temperature determine the 



value of —log \e,/T */ corresponding to the initial temperature (°C.) from part C, add 

 to this the value of —log (£7/100) from part D. As shown by equation (3) the sum is 



— log \e,e/T e J . Enter part C of the table with this sum as the tabular value. The 

 corresponding argument is the condensation temperature (°C). 



Lifting condensation pressure. — The corresponding condensation pressure pe may be 

 obtained by means of Poisson's equation 



e _ /looox* (4) 



To \ P. ) 



where 6 is the potential temperature, C K. Values of p e may be computed with the aid of 



Table 77 which tabulates the function (— r— ) • A more rapid means of determining 



the lifting condensation pressure for processes occuring at potential temperatures of 

 302.16, 314.16, or 330.16 °K. is provided by part E. Introducing Poisson's equation into 

 equation (3) gives 



.og (W100) + log {<■/[»/(») *]''}=log{ ,../[»/(») ']*} (5) 



where p is the pressure at the initial level. Note that e. and e. c are the saturation vapor 

 pressures at the temperatures as given by the associated expressions inside the square 



X U — e/eiX 100. See Table 93 for definition of true relative humidity. 



{continued) 



SMITHSONIAN METEOROLOGICAL TABLES 



