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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />- 57 - <br /> <br />(3.38) <br /> <br /> <br />eithe!" \-tate!" or ice. It follows from the definition of the saturation mixing <br /> <br />ratio w that <br />s <br /> <br />w <br />s <br /> <br />= <br /> <br />€e <br />s <br />p .. e <br />s <br /> <br />€e <br />s' <br />:: - <br />p <br /> <br />where, e is the saturated vapour pressure and <br />s <br /> <br />.1 <br /> <br />e = <br /> <br />R <br />R <br />v <br /> <br />where R is the gas constant for water vapour. From eqn. (3.38) <br />v <br /> <br />VUn w) = v(1n e ) - V(ln p) <br />s s <br /> <br />Also from the Clausius-Clapeyron equation <br /> <br />d(ln e ) <br />s <br />dT <br /> <br />L <br />= R T2 <br />v <br /> <br />therefore, <br /> <br />ln e <br />s <br /> <br />L <br />= - R T + (constant) <br />v <br /> <br />From eqns. (3.39), (3.40) and (3.42) <br /> <br />. ~. <br /> <br />.Lw . 1 w <br />.".-!. VT = - Vw +..!. v(1n p) . <br />RT2 ESE <br /> <br />(3.39) <br /> <br />(3.40) <br /> <br />(3.41) <br /> <br />(3.42) <br /> <br />(3.43) <br />