Changeset 3342

Timestamp:

2012-04-02T15:41:34+02:00 (12 years ago)

Author:

sga

Message:

NEMO branch dev_r3337_NOCS10_ICB: add documentation for iceberg code

Location:

branches/2012/dev_r3337_NOCS10_ICB/DOC/TexFiles

Files:

• Chapters/Chap_SBC.tex (modified) (3 diffs)
• Namelist/namberg (added)

branches/2012/dev_r3337_NOCS10_ICB/DOC/TexFiles/Chapters/Chap_SBC.tex

@@ -1 +1 @@
 % ================================================================
-% Chapter Ñ Surface Boundary Condition (SBC) 
-% ================================================================
-\chapter{Surface Boundary Condition (SBC) }
+% Chapter Ñ Surface Boundary Condition (SBC, ICB) 
+% ================================================================
+\chapter{Surface Boundary Condition (SBC, ICB) }
 \label{SBC}
 \minitoc
@@ -56 +56 @@
 Next the scheme for interpolation on the fly is described.
 Finally, the different options that further modify the fluxes applied to the ocean are discussed.
+One of these is modification by icebergs (see \S\ref{ICB_icebergs}), which act as drifting sources of fresh water.
 
 
@@ -1045 +1046 @@
 the expense of having more idle CICE processors in areas where there is no sea ice.
 
+% -------------------------------------------------------------------------------------------------------------
+%        Handling of icebergs
+% -------------------------------------------------------------------------------------------------------------
+\subsection{ Handling of icebergs (ICB) }
+\label{ICB_icebergs}
+%------------------------------------------namberg----------------------------------------------------
+\namdisplay{namberg}
+%-------------------------------------------------------------------------------------------------------------
+
+Icebergs are modelled as lagrangian particles in NEMO.
+Their physical behaviour is controlled by equations as described in Martin and Adcroft (2010).
+(Note that the authors kindly provided a copy of their code to act as a basis for implementation in NEMO.)
+Icebergs are initially spawned into one of ten classes which have specific mass and thickness as described by
+\np{rn\_initial\_mass} and \np{rn\_initial\_thickness}.
+Each class has an associated scaling (\np{rn\_mass\_scaling}), which is an integer representing how many icebergs 
+of this class are being described as one lagrangian point (this reduces the numerical problem of tracking every single iceberg).
+They are enabled by setting \np{ln\_icebergs}~=~true.
+
+Two initialisation schemes are possible.
+\begin{description}
+\item[\np{nn\_test\_icebergs}~>~0]
+In this scheme, the value of \np{nn\_test\_icebergs} represents the class of iceberg to generate (so between 1 and 10), and 
+\np{nn\_test\_icebergs} provides a lon/lat box in the domain at each grid point of which an iceberg is generated at the 
+beginning of the run. (Note that this happens each time the timestep equals \np{nn\_nit000}.)
+\np{nn\_test\_icebergs} is defined by four numbers in \np{nn\_test\_box} representing the corners of the geographical
+box: lonmin,lonmax,latmin,latmax
+\item[\np{nn\_test\_icebergs}~=~-1]
+In this scheme the model reads a calving file supplied in the \np{sn\_icb} parameter.
+This should be a file with a field on the configuration grid (typically ORCA) representing ice accumulation rate at each model point. 
+These should be ocean points adjacent to land where icebergs are known to calve.
+Most points in this input grid are going to have value zero.
+When the model runs, ice is accumulated at each grid point which has a non-zero source term.
+At each time step, a test is performed to see if there is enough ice mass to calve an iceberg of each class in order (1 to 10).
+Note that this is the initial mass multiplied by the number each particle represents (i.e. the scaling).
+If there is enough ice, a new iceberg is spawned and the total available ice reduced accordingly.
+\end{description}
+
+Icebergs are influenced by wind, waves and currents, bottom melt and erosion.
+The latter act to disintegrate the iceberg.
+This is either all melted freshwater, or (if \np{rn\_bits\_erosion\_fraction}~>~0) into melt and additionally small ice bits
+which are assumed to propagate with their larger parent and thus delay fluxing into the ocean.
+Melt water (and other variables on the configuration grid) are written into the main NEMO model output files.
+
+Extensive diagnostics can be produced.
+Separate output files are maintained for human-readable iceberg information.
+A separate file is produced for each processor (independent of \np{ln\_ctl}).
+The amount of information is controlled by two integer parameters:
+\begin{description}
+\item[\np{nn\_verbose\_level}]  takes a value between one and four and represents an increasing number of points in the code
+at which variables are written, and an increasing level of obscurity.
+\item[\np{nn\_verbose\_level}] is the number of timesteps between writes
+\end{description}
+
+Iceberg trajectories can also be written out and this is enabled by setting \np{nn\_sample\_rate}~>~0.
+A non-zero value represents how many timesteps between writes of information into the output file.
+These output files are in NETCDF format.
+When \key{mpp\_mpi} is defined, each output file contains only those icebergs in the corresponding processor,
+so care is needed to recreate data for individual icebergs.
 
 % -------------------------------------------------------------------------------------------------------------