% $Id: exercise_cbl.tex 1515 2015-01-02 11:35:51Z boeske $ \input{header_tmp.tex} %\input{header_lectures.tex} %\usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{ngerman} \usepackage{pgf} \usepackage{subfigure} \usepackage{units} \usepackage{multimedia} \usepackage{hyperref} \newcommand{\event}[1]{\newcommand{\eventname}{#1}} \usepackage{xmpmulti} \usepackage{tikz} \usetikzlibrary{shapes,arrows,positioning} \usetikzlibrary{calc} %neues paket \usetikzlibrary{decorations.markings} %neues paket \usetikzlibrary{decorations.pathreplacing} %neues paket \def\Tiny{\fontsize{4pt}{4pt}\selectfont} \usepackage{amsmath} \usepackage{amssymb} \usepackage{multicol} \usepackage{pdfcomment} \usepackage{graphicx} \usepackage{listings} \lstset{showspaces=false,language=fortran,basicstyle= \ttfamily,showstringspaces=false,captionpos=b} \institute{Institute of Meteorology and Climatology, Leibniz Universit{\"a}t Hannover} \selectlanguage{english} \date{last update: \today} \event{PALM Seminar} \setbeamertemplate{navigation symbols}{} \setbeamertemplate{footline} { \begin{beamercolorbox}[rightskip=-0.1cm]& {\includegraphics[height=0.65cm]{imuk_logo.pdf}\hfill \includegraphics[height=0.65cm]{luh_logo.pdf}} \end{beamercolorbox} \begin{beamercolorbox}[ht=2.5ex,dp=1.125ex, leftskip=.3cm,rightskip=0.3cm plus1fil]{title in head/foot} {\leavevmode{\usebeamerfont{author in head/foot}\insertshortauthor} \hfill \eventname \hfill \insertframenumber \; / \inserttotalframenumber} \end{beamercolorbox} \begin{beamercolorbox}[colsep=1.5pt]{lower separation line foot} \end{beamercolorbox} } %\logo{\includegraphics[width=0.3\textwidth]{luhimuk_logo.pdf}} \title[Exercise 10: Cumulus Cloud]{Exercise 10: \\Cumulus Cloud With Bulk Cloud Physics} \author{PALM group} \begin{document} % Folie 1 \begin{frame} \titlepage \end{frame} \section{Exercise} \subsection{Exercise} % Folie 2 \begin{frame} \frametitle{Exercise 10: Cumulus Cloud With Bulk Cloud Physics} Simulate a cumulus cloud: \begin{itemize} % \scriptsize \item<2-> Initialize the simulation with a marine, cumulus-topped, trade-wind region boundary layer. \item<3-> Trigger the cloud by a bubble of rising warm air. \item<4-> Parameterize condensation using a simple bulk cloud physics scheme. \item<5-> Learn how to carry out conditional averages. \end{itemize} \end{frame} % Folie 3 \section{Hints} \subsection{Hints} \begin{frame} \frametitle{Hints I} The setup of this exercise is based on the LES-intercomparison BOMEX (Siebesma et al., 2003, J. Atmos. Sci.): % \only<2>{\begin{center} % \includegraphics[width=0.7\textwidth]{exercise_cumulus_figures/ptq.pdf} % \end{center}} % \only<2->{ \begin{itemize} \scriptsize \item<2-> In order to prescribe vertical profiles of temperature and humidity, set:\\ \texttt{initializing\_actions = 'set\_constant\_profiles',} \item<3-> \texttt{pt\_surface = 297.9,} \texttt{pt\_vertical\_gradient = 0.0, 0.58588957,} \texttt{pt\_vertical\_gradient\_level = 0.0, 740.0,} \item<4-> \texttt{q\_surface = 0.016,} \texttt{q\_vertical\_gradient = -2.97297E-4, -4.5238095E-4, -8.108108E-5,} \texttt{q\_vertical\_gradient\_level = 0.0, 740.0, 3260.0,} \item<5-> \texttt{surface\_pressure = 1015.4,} \item<6-> Note that contrary to BOMEX, no geostrophic wind, no surface fluxes, and no subsidence is prescribed in this setup. \item<7-> domain size: about $\unit[1000 \times 3600 \times 3000]{m^3}$ ($x$/$y$/$z$) \item<8-> grid size: $\unit[50]{m}$ equidistant \item<9-> simulated time: $\unit[1800]{s}$ \end{itemize} % } \end{frame} % Folie 4 \begin{frame} \frametitle{Hints II} How to initialize a bubble of warm air? \begin{itemize} \scriptsize \item<2-> In the subroutine \texttt{user\_init}, initialize the bubble of warm air by a temperature excess at the first time step (\texttt{current\_timestep\_number == 0}) \item<3-> The temperature excess can be added directly to the three-dimensional field of liquid water potential temperature: \texttt{pt(k,j,i) = pt(k,j,i) + EXP( -0.5 * ( y / bubble\_sigma\_y )**2 ) * \&} \texttt{\hphantom{pt(k,j,i) = pt(k,j,i) + }EXP( -0.5 * ( z / bubble\_sigma\_z )**2 ) * \&} \texttt{\hphantom{pt(k,j,i) = pt(k,j,i) + }initial\_temperature\_difference} with the locations: \texttt{y = j * dy - bubble\_center\_y} \texttt{z = zu(k) - bubble\_center\_z} \item<4-> Initialize the bubble by the following parameters: \texttt{bubble\_center\_y = 1800.0, bubble\_center\_z = 170.0,} \texttt{bubble\_sigma\_y = 300.0, bubble\_sigma\_z = 150.0,} \texttt{initial\_temperature\_difference = 0.4} \item<5-> Think parallel: Mind that the domain of each PE extends only from \texttt{nxlg} to \texttt{nxrg} and \texttt{nysg} to \texttt{nyng}! (Note that the just mentioned dimensions include ghost points) \end{itemize} \end{frame} % Folie 5 \begin{frame} \frametitle{Hints III} Bulk cloud physics in PALM: \begin{itemize} \scriptsize \item<2-> PALM offers two bulk cloud physics schemes: A very simple, one-moment scheme by Kessler (1969, Meteor. Monogr.) and a state-of-the-art two-moment scheme by Seifert and Beheng (2006, Meteor. Atmos. Phys.). \item<3-> You will use the saturation adjustment scheme, as applied in the Kessler-scheme, for parameterizing condensation. (Note that this kind of scheme is used in the vast majority of today's bulk cloud physics parameterizations.) \item<4-> The liquid water is diagnosed by $q_\text{l} = \max(0, q_\text{t} - q_\text{s})$: If the total water content $q_\text{t}$ exceeds the saturation water content $q_\text{s}$, all supersaturations condensate immediately to liquid water. On the other hand, no liquid water is present in subsaturated conditions. \end{itemize} \onslide<4-> Turn on simple cloud microphysics in your parameter file (\texttt{inipar} namelist): \begin{itemize} \scriptsize \item<5-> \texttt{humidity = .TRUE., cloud\_physics = .TRUE.,} \item<6-> \texttt{cloud\_scheme = 'kessler', precipitation = .FALSE.} \end{itemize} \end{frame} % Folie 6 \begin{frame} \frametitle{Hints IV} What is conditional averaging? \begin{itemize} \scriptsize \item<2-> A horizontal average (e.\,g., for retrieving vertical profiles) might be inappropriate for the analysis of a heterogeneous phenomenon (e.\,g., cumulus clouds). \item<3-> A conditional average can restrict the analysis to the regions of interest (e.\,g., cloudy and non-cloudy regions). \end{itemize} \onslide<4->What kind of conditional average are you going to derive? \begin{itemize} \scriptsize \item<5-> You will derive vertical profiles of \textbf{cloud cover} and \textbf{cloud core cover}. These profiles are the basis for more complex profiles (e.\,g., the cloud core vertical velocity). \item<6-> Cloudy grid cells are defined as grid cells with a non-zero liquid water content ($q_\text{l}>0$, \texttt{ql(k,j,i) > 0.0}). Cloud core grid cells are defined as cloudy grid cells, which are also positively buoyant with respect to the slab average ($\theta_\text{v}>\langle \theta_\text{v} \rangle$, \texttt{vpt(k,j,i) > hom(k,1,44,sr)}). \end{itemize} \end{frame} % Folie 7 \begin{frame} \frametitle{Hints V} PALM offers a convenient way to compute and output user-profiles: \begin{itemize} \scriptsize \item<2-> In the subroutine \texttt{user\_statistics}, you can compute the cloud cover profile by counting all cloudy grid cells at a certain grid level \texttt{k}: \texttt{IF ( ql(k,j,i) > 0.0 ) THEN} \texttt{\hphantom{aaa}sums\_l(k,pr\_palm+1,tn) = sums\_l(k,pr\_palm+1,tn) + 1.0} \texttt{ENDIF} \item<3-> The computation of the cloud core cover profile is up to you! \item<4-> PALM automatically cares for the summation across the PE's boundaries and the normalization of the profiles (i.\,e., dividing it by the total amount of grid cells in horizontal directions). \item<5-> Do not forget to adapt \texttt{user\_check\_data\_output\_pr} (for defining your user-profiles) and your parameter file (\texttt{userpar} namelist) for the output (with the parameter \texttt{data\_output\_pr\_user = 'your\_profile'})! \item<6-> Check the online documentation of PALM for more detailed information on the implementation of user profiles:\\ \texttt{\hphantom{aaa}http://palm.muk.uni-hannover.de/trac/wiki/doc/app/userint/output\#part\_1}\\ Further examples are also provided within the subroutines \texttt{user\_statistics} and \texttt{user\_check\_data\_output\_pr}. \end{itemize} \end{frame} \section{Tasks} \subsection{Tasks} % Folie 8 \begin{frame} \frametitle{Tasks to be done:} \begin{itemize} \item<1-> Output instantaneous yz-cross sections of \texttt{ql} and \texttt{w} at \texttt{section\_yz = 0}. (\texttt{pt}, \texttt{q} and \texttt{vpt} are also interesting!) An output interval of $60\,\text{s}$ is adequate. \item<2-> Output instantaneous vertical profiles of cloud cover and cloud core cover! Again, an output interval of $60\,\text{s}$ is adequate. \item<3-> Answer the following questions: \begin{itemize} \item How does the cloud develop? \item Can you identify the \textit{actively growing} and the \textit{decaying stage} of the cloud's life cycle by comparing the profiles of cloud and cloud core cover profiles? (Mind the profiles' definitions and physical implications!) \end{itemize} \item<4-> If you are really fast: What changes during the cloud's development turning on precipitation (\texttt{precipitation = .TRUE.})? \end{itemize} \end{frame} % Folie 9 \section{Results} \subsection{Results} \begin{frame} \frametitle{$yz$-cross sections at $t \approx \unit[500]{s}$} % The bubble of warm air rises, but has not reached its condensation level. \vspace{-5mm} \begin{center} \includegraphics[angle=90,width=1.0\textwidth]{exercise_cumulus_figures/500.pdf} \end{center} \end{frame} % Folie 8 \begin{frame} \frametitle{$yz$-cross sections at $t \approx \unit[800]{s}$} % Condensation starts, and the cloud appears as the the visible top of the rising bubble. \vspace{-5mm} \begin{center} \includegraphics[angle=90,width=1.0\textwidth]{exercise_cumulus_figures/800.pdf} \end{center} \end{frame} % Folie 9 \begin{frame} \frametitle{$yz$-cross sections at $t \approx \unit[1200]{s}$} % The cloud is vigorously growing. \vspace{-5mm} \begin{center} \includegraphics[angle=90,width=1.0\textwidth]{exercise_cumulus_figures/1200.pdf} \end{center} \end{frame} % Folie 9 \begin{frame} \frametitle{$yz$-cross sections at $t \approx \unit[1500]{s}$} % The cloud dilutes and dissipates due to turbulent entrainment of environmental air. \vspace{-5mm} \begin{center} \includegraphics[angle=90,width=1.0\textwidth]{exercise_cumulus_figures/1500.pdf} \end{center} \end{frame} % Folie 10 \begin{frame} \frametitle{Cloud cover (clcov) and cloud core cover (cocov) profiles} \begin{center} \includegraphics[width=1.0\textwidth]{exercise_cumulus_figures/prof.pdf} \end{center} \end{frame} %\section{Answers} \subsection*{Answers} % Folie 13 \begin{frame} \frametitle{Answers to questions I} {\footnotesize } How does the cloud develop? {\footnotesize } \begin{itemize} \item See frames 9 -- 12: The clouds develops from a rising bubble of warm air ($t \approx \unit[500]{s}$). Reaching the condensation level ($t \approx \unit[800]{s}$), the cloud appears as the bubble's visible top. Afterwards, the cloud starts to grow more vigorously by the release of latent heat ($t \approx \unit[1200]{s}$). In the end of the cloud's life-cycle, the cloud dissipates by turbulent entrainment of environmental air and the subsequent evaporation of the cloud ($t \approx \unit[1500]{s}$). \end{itemize} \end{frame} \begin{frame} \frametitle{Answers to questions II} {\footnotesize } Can you identify the (i) actively growing and (ii) decaying stage of the cloud's life cycle by comparing the profiles of cloud and cloud core cover profiles? {\footnotesize } \begin{itemize} \item See Frame 13: As long as the cloud core is present, i.\,e., a positively buoyant region producing upward motion, the cloud grows actively (until $1400\,\text{s}$). From $1500\,\text{s}$ on, no cloud core is visible. As a result, the cloud's upward motion decelerates and the rate of condensation decreases. Thus, the cloud's dilution by the entrainment of environmental air can not be counterbalanced anymore. As a consequence, the cloud decays and finally dissipates. \end{itemize} \end{frame} \begin{frame} \frametitle{Answers to questions III} {\footnotesize } What changes during the cloud's development turning on precipitation (\texttt{precipitation = .TRUE.})? {\footnotesize } \begin{itemize} \item Almost nothing. The simulated cloud is very shallow, therefore no significant masses of rain are produced that might alter the cloud. \end{itemize} \end{frame} \end{document}