The specific humidity  $q_s$ is a function of temperature $T$. Its values are : 
\begin{equation}
q_s(T) = 
\begin{cases}
0 & \text{if} \quad T < 100K \\
\dfrac{M_{air}}{M_{vapor}} \cdot 10^{2.07203 - 0.0032099T - \frac{2484.896}{T} + 3.56654\log{T}} & \text{if} \quad 100K \leq T < 273K \\
\dfrac{M_{air}}{M_{vapor}} \cdot 10^{23.819 - \frac{2948.964}{T} -
  5.028\log{T} - 29910.16\exp(-0.0699832\times T) + 25.21935\exp(-\frac{2999.924}{T}) } & \text{if} \quad 273K \leq T \leq 370K \\
\end{cases} %\]
\end{equation}
where : \\
\begin{itemize}
 \item  $\dfrac{M_{air}}{M_{vapor}} = \dfrac{18.02 \times 10^{-3}}{28.964 \times 10^{-3}} \simeq 0.622 $ is the ratio between the molecular weight of dry air and \\ 
the molecular weight of water vapor.
 \item  $\log(T) = \dfrac{\ln T}{\ln 10}$
\end{itemize}

