\chapter{Introduction}

The Climate Data Operators ({\CDO}) software is a collection of many operators
for standard processing of climate and forecast model data.
The operators include simple statistical and arithmetic functions, data selection
and subsampling tools, and spatial interpolation.
%{\CDO} is a collection of Operators to manipulate and analyse Climate model Data.
%There are a lot of operators for doing standard processing like simple statistic,
%arithmetic, selection and interpolation on datasets from climate and forecast models.
%The operators are primarily designed to aid manipulation and analysis of gridded scientific data
{\CDO} was developed to have the same set of processing functions for GRIB \cite{GRIB} and NetCDF \cite{NetCDF}
datasets in one package.

The Climate Data Interface \cite{CDI} is used for the fast and file format
independent access to GRIB and NetCDF datasets.
The local \href{http://www.mpimet.mpg.de/}{MPI-MET} data formats SERVICE, EXTRA and 
IEG are also supported.

There are some limitations for GRIB and NetCDF datasets.
A GRIB dataset has to be consistent, similar to NetCDF.
That means all time steps need to have the same variables, and
within a time step each variable may occur only once.
NetCDF datasets are only supported for the classic data model and arrays up to 4 dimensions.
These dimensions should only be used by the horizontal and vertical grid and the time.
The NetCDF attributes should follow the
\href{http://ftp.unidata.ucar.edu/software/netcdf/docs/conventions.html}
     {GDT, COARDS or CF Conventions}.

The user interface and some operators are similar to the PINGO \cite{PINGO} package.
% There are also some operators with the same name as in PINGO but with a 
% different meaning. \htmlref{Appendix A}{appendixpingo} gives an overview of 
% xsthose operators.

The main {\CDO} features are:
\begin{itemize}
\item More than 700 operators available
\item Modular design and easily extendable with new operators
\item Very simple UNIX command line interface
\item A dataset can be processed by several operators,
      without storing the interim results in files % (No disk I/O).
\item Most operators handle datasets with missing values
\item Fast processing of large datasets
\item Support of many different grid types
\item Tested on many UNIX/Linux systems, Cygwin, and MacOS-X
%item Free available and runs on all UNIX platforms.
\end{itemize}

\input{install}

\input{usage}

\input{grid}

\input{zaxis}

\input{time}

\input{partab}

\input{missval}

\input{percentile}
