
\def\V{{\bf v}}
\def\ave#1{\overline{#1}}
\def\mave#1{\tilde{#1}}
\def\q{c}

\begin{frame}
 \frametitle{Limitations of turbulent diffusion}


{\bf Assumption leading to the diffusive approach : }
\begin{itemize}
\item Turbulence as a random process
\item Small scale turbulence, i.e. of size $l << h$ with $h={\depb{\frac{1}\q\der{\q}{z}}}^{-1}$ 
\end{itemize}

{\bf In the planetary boundary layer}
\begin{itemize}
\item Long range vertical transport (from the bottom to PBL top)
\item Organized structures
\end{itemize}

{\small
\begin{columns}
\column{0.5\textwidth}
\includegraphics[bb= -10 600 530 900,clip,height=3cm]{/home/hourdin/PRESENTATIONS/IMAGES/NUAGES/RUES/PDF/20090302france.pdf}\\
Cloud streets on North of France (March 2009, MSG)
\column{0.25\textwidth}
\includegraphics[height=3cm,bb= 20 -50 500 455]{/home/hourdin/PRESENTATIONS/IMAGES/PBL/PDF/w2bb.pdf}
\column{0.25\textwidth}
Radar echoes\\
dry convective boundary layer\\
Florida, Hiop Campaign\\
{\tiny Weckwerth et al., 1997}
\end{columns}
}
\end{frame}
