\begin{table}%t2
  \caption{Parameter sets for the description of maritime and continental water clouds by a log-normal distribution.}
  \label{tab2}
  %\centering
\par
  \begin{tabular}{l c c}
    \hline\hline
    \noalign{\smallskip}
    Parameter & Maritime clouds & Continental clouds\\
    \hline
    \noalign{\smallskip}
    $n \ ({\rm cm^{-3}})$ & 91.0 & 254.0 \\
    $a_{\rm m} \ ({\rm K})$ & 6.0 & 4.0 \\
    $\sigma$ & 0.4 & 0.4 \\
    \hline
    \noalign{\smallskip}
  \end{tabular}
\end{table}