Community Ice CodE (CICE) User's Guide Version 4.0 Released
Contents
1. 19 continued from previous page f_fsalt f_fsalt_ai f_fhnet f_fhnet_ai f_fswthru f_fswthru_ai f_strairx f_strairy f_strtltx f_strtlty f_strcorx f_strcory f_strocnx f_strocny f_strintx f_strinty f_strength f_divu f_shear f_opening f_sigi f_sig2 f_daidtt f_daidtd f_dvidtt f_dvidtd f_mlt_onset f_frz_onset 10 Troubleshooting ice to ocn salt flux sent to coupler ice to ocn salt flux ice ocn net heat flux sent to coupler ice ocn net heat flux SW transmitted through ice to ocean sent to coupler SW transmitted through ice to ocean zonal atm ice stress meridional atm ice stress zonal sea surface tilt meridional sea surface tilt zonal coriolis stress meridional coriolis stress zonal ocean ice stress meridional ocean ice stress zonal internal ice stress meridional internal ice stress compressive ice strength velocity divergence strain rate lead opening rate normalized principal stress component normalized principal stress component area tendency due to thermodynamics area tendency due to dynamics ice volume tendency due to thermo ice volume tendency due to dynamics melt onset date freeze onset date 10 1 Code does not Compile or Run Check the ice log or ice bldlog files in the executable directory or the standard output and error files for information Also try the following e Delete the executable directory and rebuild the model e Make sure that there is a Macro2. 3 9 Example Namelists This section shows several examples of namelists from the coupled ice model These examples are taken directly from cice buildnml csh for the coupled model Most of the variables in the namelist are determined from environment variables set elsewhere in the scripts Since the namelists from the coupled model are resolved by the scripts meaning that the values of most of the shell script variables are put directly into the namelist examples are shown for the most commonly used configurations Variables that are commonly 10 Table 7 Namelist Variables for Domain Decomposition Information Varible Type Default Description Value processor_shape Character square pop Approximate block shapes ew_boundary_type Character cyclic Boundary conditions in E W direction ns_boundary_type Character open Boundary conditions in N S direction distribution_type Character cartesian How blocks are split onto processors cartesian spacecurve rake distribution_wght Character erfe How blocks are weighted when using space filling curves erfc or file distribution_wght_file Character q File containing space filling curve weights when not using erfc weighting Table 8 Namelist Variables for Parallel I O Varible Type Default Value Description ice _num_iotasks Integer 1 Number of I O tasks default 1 selects all processors ice_pio_stride Integer 1 Stride between I O tasks
3. mxxxx f_meltt mxxxx f_mlt_onset XXXXXx f_opening mxxxx f_shear mxxxx f_sigl mxxxx f_sig2 mxxxx f_snoice mxxxx f_sss XXXxXx f_sst XXXxXx f_strairx mxxxx f_strairy MXXXX f_strcorx mxxxx f_strcory MXXXX f_strength mxxxx f_strintx mxxxx f_strinty MXXXxX f_strocnx mxxxx f_strocny MXXXxX f_strtltx XxXxxx f_strtlty XXXXX f_uocn XXXxXx f_uvel mxxxx f_vicen mxxxx f_vocn XXXxXx f_vvel mxxxx 4 Model Input Datasets The coupled CICE model requires a minimum of three files to run e global_ ICE_GRID grid is a binary file containing grid information e global_ ICE_GRID kmt is a binary file containing land mask information e iced 0001 01 01 ICE_GRID 20lay are binary files containing initial condition information for the gxlv6 and gx3v7 grids respectively The thickness distribution in this restart file contains 5 categories each with 4 layers 13 Depending on the grid selected in the scripts the appropriate global and iced files will be used in the executable directory These files are read directory from the system input data directory and not copied to the executable directory Currently only gx3v7 gxlv6 txlvl and tx0 1v2 grids are supported for the ice and ocean models Note that these files can now be used in netCDF format 5 Run Types The run types available for th
4. stream_year_last Integer 1 Last year of prescribed ice data model_year_align Integer 1 Year in model run that aligns with stream_year _first stream_domfilename Character Prescribed ice stream data file stream_fldfilename Character Prescribed ice stream data file stream_fldvarname Character ice_cov Ice fraction field name Table 6 Namelist Variables for Grid and Mask Information Varible Type Default Value Description grid_type Character displaced_pole Determines grid type displaced pole tripole rectangular grid_format Character binary Grid file format binary or netCDF grid_file Character data domain grid Input filename containing grid informa tion kmt_file Character data domain kmt Input filename containing land mask in formation kcatbound Integer 0 How category boundaries are set 0 or 1 For coupled runs supported grids include the displaced_ pole grids gx3v7 and gxlv6 and the tripole grids 3 7 Domain Namelist The namelist parameters listed in Table 7 are for computational domain decomposition information These are generally set in the build configure scripts based on the number of processors See the CESM scripts documentation 3 8 PIO Namelist The namelist parameters listed in Table 8 are for controlling parallel input output Only a brief overview will be given here but more on parallel input output can be found at http web ncar teragrid org dennis pio_doc html
5. 1 selects defaulto stride ice pio type nameCharacter netcdf Underlying library used default is netcdf changed directly in the namelist are the timestep dt and the number of subcycles per timestep in the ice dynamics ndte 3 9 1 Example 1 CESM Fully Coupled The following example is the namelist used for CESM fully coupled or the B configuration The variables that are still set to shell script variables have been set at the top of cice buildnml csh or in other scripts A completely resolved version of the namelist will be written to ice_in in the executable directory amp setup_nml diagfreq hist_avg histfreq histfreq_n ice_ic 1cdf64 pointer_file xndt_dyn amp grid_nml grid_file 10402 grid grid_format grid_type kcatbound kmt_file 24 true 2m 3 dx 2x 5 2x 2x 1 114 1 b40 1850 track1 1deg 006 cice r 0301 01 01 00000 nc false gt rpointer ice 1 0 fis cgd cseg csm inputdata ice cice global_gx1v6_200 gt bin gt displaced_pole 0 fis cgd cseg csm inputdata ice cice global_gx1v6_200 11 90204 kmt amp ice_nml advection albedo_type albicei albicev albsnowi albsnowv evp_damping kdyn 1 kitd at krdg_partic e krdg_redist kstrength ndte 120 r_snw 1 5 shortwave amp tracer_nml tr_aero true tr_FY true tr_iage true tr_pond true amp domain_nml distribution_type ew_boundary_type ns_bounda
6. This thickness is a parameter that can be changed in ice_shortwave F90 The snow albedos are for cold snow For the new delta Eddington shortwave radiative transfer scheme Briegleb and Light 2007 the base albedos are computed based on the inherent optical properties of snow sea ice and melt ponds These albedos are tunable through adjustments to the snow grain radius R_snw temperature to transition to melting snow and maximum snow grain radius 3 4 Tracer Namelist The namelist parameters listed in Table 4 are for adding tracers See section on tracers 3 5 Prescribed Ice Namelist The namelist parameters listed in Table 5 are for the prescribed ice option as used in AMIP and F compset standalone CAM runs 6 3 6 Grid Namelist The namelist parameters listed in Table 6 are for grid and mask information During execution the ice model reads grid and land mask information from the files grid file and kmt_file that should be located in the executable directory There are commands in the scripts that copy these files from the input data directory rename them from global_ ICE_GRID grid and global_ ICE_GRID kmt to the default filenames shown in Table 6 Table 5 Namelist Variables for Prescribed Ice Option Varible Type Default Value Description prescribed_ice Logical false Flag to turn on prescribed ice prescribed_ice_fill Logical false Flag to turn fill option stream_year_first Integer 1 First year of prescribed ice data
7. as dte dt ndte and must be sufficiently smaller than the damping timescale T which needs to be sufficiently shorter than dt dte lt T lt dt 2 This relationship is discussed in Hunke 2001 also see Hunke and Lipscomb 2008 section 4 4 The best ratio for dte T dt is 1 40 120 Typical combinations of dt and ndte are 3600 120 7200 240 10800 120 The default ndte is 120 as set in ice_init F90 kitd determines the scheme used to redistribute sea ice within the ice thickness distribution ITD as the ice grows and melts The linear remapping scheme is the default and approximates the thickness distribution in each category as a linear function Lipscomb 2001 The delta function method represents g h in each Table 3 Namelist Variables for Model Physics Varible Name Type Default Value Description ndte Integer 1 Number of sub cycles in EVP dynamics kcolumn Integer 0 Column model flag 0 off 1 column model not tested or sup ported kitd Integer 1 Determines ITD conversion 0 delta scheme 1 linear remapping kdyn Integer 1 Determines ice dynamics 0 No ice dynamics 1 Elastic viscous plastic dynamics kstrength Integer 1 Determines pressure formulation 0 Hibler 1979 parameterization 1 Rothrock 1975 parameterization evp_damping Logical false If true use damping procedure in evp dy namics not supported advection Character remap Determines horizontal advection scheme r
8. model scripts or namelists or running the uncoupled ice model Users interested in modifying the source code should see the CICE Code Reference Developer s Guide CICE4 is the latest version of the Los Alamos Sea Ice Model sometimes referred to as the Community Ice CodE It is the result of a community effort to develop a portable efficient sea ice model that can be run coupled in a global climate model or uncoupled as a stand alone ice model It has been released as the sea ice component of the Community Earth System Model CESM a fully coupled global climate model that provides simulations of the earths past present and future climate states CICE4 is supported on high and low resolution Greenland Pole and tripole grids which are identical to those used by the Parallel Ocean Program POP ocean model The high resolution version is best suited for simulating present day and future climate scenarios while the low resolution option is used for paleoclimate simulations and debugging An uncoupled version of CICE is available separately from Los Alamos National Laboratory http oceansi1 lanl gov trac CICE It provides a means of running the sea ice model independent of the other CESM components It reads in atmospheric and ocean forcing which eliminates the need for the flux coupler and the atmosphere land and ocean data models It can be run on a reduced number of processors or without MPI Message Passing Interface for researchers witho
9. 849 1867 Hunke E C and W H Lipscomb 2008 CICE The Los Alamos Sea Ice Model Documentation and Software User s Manual Version 4 0 T 3 Fluid Dynamics Group Los Alamos National Laboratory Tech Rep LA CC 06 012 Lipscomb W H 2001 Remapping the thickness distribution in sea ice models J Geophys Res 106 13 989 14 000 Lipscomb W H and E C Hunke 2004 Modeling sea ice transport using incremental remapping Mon Wea Rev 132 1341 1354 Rothrock D A 1975 The energetics of the plastic deformation of pack ice by ridging J Geophys Res 80 4514 4519 Thorndike A S D S Rothrock G A Maykut and R Colony 1975 The thickness distribution of sea ice J Geophys Res 80 4501 4513 22
10. Community Earth System Model National Center for Atmospheric Research Boulder CO http www cesm ucar edu models Community Ice CodE CICE User s Guide Version 4 0 Released with CESM1 0 David Bailey Marika Holland Elizabeth Hunke Bill Lipscomb Bruce Briegleb Cecilia Bitz Julie Schramm Contents 1 Introduction dele Whats new in CIC AY ee oe detalles ee he ee ae ga he ed Ee Eee goa a te we SE 2 es 2 The CICE Scripts 2 1 Coupled Mod l Seripts iaa oo a0 PO e GEE A SESE TRE Ee Oe ba 2 2 The Build Environment 2 2 1 CICE Preprocessor Flags ee 3 Namelist Variables 3 1 Changing the timestep a sa a a e e aw al aa 3 2 Writing Outputs fot Pe ee ok he Ee a Ed ee EI hee ee AEE ce ah 3 39 Model Physics y a sasha eG Gosh oh oe A A O We A 3 4 Tracet Namelist aye ee ek hd Bac ih ee A Ee ES BB Sle Se San ee See da 3 5 Prescribed Ice Namelist 2 a maere a aaa ee 3 6 Grd Namelist 264 nek edhe eo one a eee ORE Ele e Bee 3 Domain Namelist Vi 248 beh A Pew EM we eee ee ee a 3 81 PIO Namelist es oy eee odd A ee eo OAS a e ee Oh eh Baa a ee ia 3 9 Example Namelists 2 io s m dada be bbe a ewe eee ed 3 9 1 Example 1 CESM Fully Coupled 0 0 0 000000 00000 3 9 2 Example 2 History File Namelist e 0 0 00 o 4 Model Input Datasets 5 Run Types 6 Prescribed Ice Mode 7 Prescribed Aerosol Mode 8 Changing the Number of Ice Thickness Categories 9 Out
11. The variables in upper case letters are set during the CESM configure step and passed through to the CICE namelist The ice concentration variable is assumed to be ice_cov There also needs to be a reconizable time axis like days since 0001 01 01 in the netCDF file so that the time interpolation can be handled within the ice model 7 Prescribed Aerosol Mode As of CESM version 1 prescribed aerosols are now handled within CAM or DATM 8 Changing the Number of Ice Thickness Categories The number of ice thickness categories affects ice model input files in three places e NCAT in the run script 14 e The source code module ice_model_size F90 e The initial condition restart file in the input file directory The number of ice thickness categories is set in CASE Buildconf cice buildexe csh using the vari able called NCAT The default value is 5 categories NCAT is used to determine the CPP variable setting NCAT in ice_model_size F90 RES is the resolution of the grid 100x116 gx3v7 and 320x384 gx1v6 for low and medium resolution grids respectively NOTE To use one ice thickness category the following changes will need to be made in the namelist kitd 0 kstrength 0 With these settings the model will use the delta scheme instead of linear remapping and a strength parameterization based on open water area and mean ice thickness The information in the initial restart file is dependent on the number of ice thi
12. able at Los Alamos National Laboratory at http oceans11 lanl gov trac CICE 2 The CICE Scripts The setup scripts for the coupled model are located in cesm1 scripts The directory structure of CICE4 within CESM is shown below cesm1 main directory models o 25 scripts k ok ok ok k ok ok bld ES ice build scripts for coupled model Makefile KOK k OK OK ok ok ok ok OK macros cice active ice component bid dogs mai src CICE documentation drivers mpi serial source cice4 cpl_esmf cpl_mct cpl_share 2 1 Coupled Model Scripts The CESM1 scripts have been significantly upgraded from CCSM3 and are based on a completely different design philosophy The new scripts will generate a set of resolved scripts for a specific configuration deter mined by the user The configuration includes components resolution run type and machine The run and setup scripts that were previously in the scripts directory for CCSM3 are now generated automatically See the CESM1 User s Guide for information on how to use the new scripts http www cesm ucar edu models cesm1 0 cesm_doc book1 html The file that contains the ice model namelist is now located in CASE Buildconf The script containing the environment variables used for building the executable file for the ice model is also in C ASE Buildconf The contents of t
13. aging interval in the history file This will give an idea of how many zeros were included in the average The second caveat results from the coupler multiplying fluxes it receives from the ice model by the ice area Before sending fluxes to the coupler they are divided by the ice area in the ice model These are the fluxes that are written to the history files they are not what affects the ice ocean or atmosphere nor are they useful for calculating budgets The division by the ice area also creates large values of the fluxes at the ice edge The affected fields are e Flat Fsens latent and sensible heat fluxes e Flwout outgoing longwave e evap evaporative water flux e Fresh ice ocn fresh water flux Fhnet ice ocn net heat flux Fswabs snow ice ocn absorbed solar flux When applicable two of the above fields will be written to the history file the value of the field that is sent to the coupler divided by ice area and a value of the flux that has been multiplied by ice area what affects the ice Fluxes multiplied by ice area will have the suffix _aice appended to the variable names in the history files Fluxes sent to the coupler will have sent to coupler appended to the long_name Fields of rainfall and snowfall multiplied by ice area are written to the history file since the values are valid everywhere and represent the precipitation rate on the ice cover 9 3 2 Changing Frequency and Averaging The frequency at whic
14. ain script In this case a value of 4 would work and the task geometry would also have to be changed 10 6 Enabling the Debugger This section explains how to set some compiler options for debugging For the coupled model set DEBUG to TRUE in the env_run xml script Before running the model be sure to delete the object files so that the source code will be recompiled If a core file is created it will be in the executable directory Use dbx to look at the core file Useful information may also appear in the standard error and output files 21 References Bitz C M M Holland M Eby and A J Weaver 2001 Simulating the ice thickness distribution in a coupled climate model J Geophys Res 106 2441 2463 Bitz C M and W H Lipscomb 1999 An energy conserving thermodynamic model of sea ice J Geophys Res 104 15 669 15 677 Briegleb B P and B Light 2007 A Delta Eddington Multiple Scattering Parameterization for Solar Radiation in the Sea Ice Component of the Community Climate System Model NCAR Technical Note NCAR TN 472 STR National Center for Atmospheric Research Boulder Colorado Hibler W D 1979 A dynamic thermodynamic sea ice model J Phys Oceanogr 9 815 846 Hunke E C 2001 Viscous plastic sea ice dynamics with the evp model Linearization issues J Comp Phys 170 18 38 Hunke E C and J K Dukowicz 1997 An elastic viscous plastic model for sea ice dynamics J Phys Oceanogr 27 1
15. cessary if coupling to an active ocean model The frequency at which restart files are created is controlled by the namelist parameter dumpfreq The names of these files are proceeded by the namelist parameter dump_file and by default are written out yearly to the executable directory To change the directory where these files are located modify the variable RSTDIR at the top of the setup script The names of the restart files follow the CESM Output Filename Requirements The form of the restart file names are as follows CASE cice r yyyy mm dd sssss nc For example the file CASE cice r 0002 01 01 00000 nc would be written out at the end of year 1 month 12 A file containing the name of a restart file is called a restart pointer file This filename information allows the model simulation to continue from the correct point in time and hence the correct restart file Restart Pointer Files A pointer file is an ascii file named rpointer ice that contains the path and filename of the latest restart file The model uses this information to find a restart file from which initialization data is read The pointer files are written to and then read from the executable directory For startup runs a pointer is created by the ice setup script Whenever a restart file is written the existing restart pointer file is overwritten The namelist variable pointer_file contains the name of the pointer file Pointer files seldom need editing The contents are usuall
16. ckness categories and the total number of layers in the ice distribution An initial condition file exists only for the default case of 5 ice thickness categories with four layers in each category To create an initial condition file for a different number of categories or layers these steps should be followed e Set NCAT to the desired number of categories in CASE Buildconf cice buildexe csh e Set the namelist variable dumpfreq m in CASE Buildconf cice buildnml csh to print out restart files monthly e Set the namelist variable restart false in CASE Buildconf cice buildnml csh to use the initial conditions within the ice model e Run the model to equilibrium e The last restart file can be used as an initial condition file e Change the name of the last restart file to iced 0001 01 01 8GRID e Copy the file into the input data directory or directly into the the executable directory Note that the date printed inside the binary restart file will not be the same as 0001 01 01 For coupled runs BASEDATE will be the starting o date and the date inside the file will not be used 9 Output Data The ice model produces three types of output data A file containing ASCII text also known as a log file is created for each run that contains information about how the run was set up and how it progressed A series of binary restart files necessary to continue the run are created A series of netCDF history files containing gridd
17. config config_cache xml csmdata DIN_LOC_ROOT infile ccsm_namelist inputdata CASEBUILD cice input_data_list A namelist amp cice CICE_NAMELIST_OPTS exit 1 Again the typical usage of the build namelist tool is through the CESM scripts but can be called via the command line interface 2 2 1 CICE Preprocessor Flags Preprocessor flags are activated in the form Doption in the cice buildexe csh script Only advanced users should change these options See the CESM User s Guide or the CICE reference guide for more information on these The flags specific to the ice model are CPPDEFS CPPDEFS DCESMCOUPLED Dcoupled Dncdf DNCAT 5 DNXGLOB O DNYGLOB DNTR_AERO 3 DBLCKX DBLCKY DMXBLCKS The options DCESMCOUPLED and Dcoupled are set to activate the coupling interface This will include the source code in ice_comp_mct F90 for example In coupled runs the CESM coupler multiplies the fluxes by the ice area so they are divided by the ice area in CICE to get the correct fluxes The options DBLCKX CICE_BLCKX and DBLCKY CICE_BLCKY set the block sizes used in each grid direction These values are set automatically in the scripts for the coupled model Note that BLCKX and BLCKY must divide evenly into the grid and are used only for MPI grid decomposition If BLCX or BLCKY do not divide evenly into the grid which determines the number of blocks in each direction the model setup will exit from the se
18. dynamics This is usually a problem with the forcing but sometimes can be indicative of a timestep problem in the ice Thermo iteration does not converge istep1 my_task i j 10 4 Conservation Error This error is written from ice_itd F when the ice model is checking that initial and final values of a conserved field are equal to within a small value The output looks like Conservation error vice add_new_ice 11 14 185 Initial value 1362442 600400560 Final value 1362442 600400561 Difference 2 328306436538696D 10 shr_sys_abort ERROR ice Conservation error shr_sys_abort WARNING calling shr_mpi_abort and stopping shr_mpi_abort ice Conservation error 0 Non conservation can occur if the ice model is receiving very bad forcing and is not able to deal with it This has occurred after a CFL violation in the ocean The timestep in the ocean may be decreased to get around the problem 10 5 NX does not divide evenly into grid If you modify the number of tasks used by the ice model the model may stop with this error written to the log file ERROR NX must divide evenly into grid 100 8 The number of MPI processors used by the ice model must divide evenly into the grid dimensions For example running the ice model with 8 tasks on the gx3v7 grid will result in an error since 8 does not divide evenly into the 100 longitude points To fix this error change the value of NTASKS for the uncoupled ice model in the m
19. e coupled model are described in the CESM User s Guide http www cesm ucar edu models cesm1 0 cesm_doc book1 html 6 Prescribed Ice Mode The prescribed ice mode is a functionality feature that is needed for certain standalone CAM runs such as AMIP Atmospheric Model Intercomparison Project style runs In this mode the sea ice concentration is read from a file and replaces the prognostic concentrations computed in the model The sea ice dynamics is turned off in this mode and the sea ice thickness is reset to 2 m in the northern hemisphere and 1 m in the southern at every timestep The main purpose of this mode is to compute the surface fluxes snow depth albedos and surface temperature over the ice by using the 1D thermodynamics in the sea ice model This mode is not energy conserving and is mainly intended as a testbed for atmospheric sensitivity experiments The input netCDF file name required for this prescribed mode is set in the CESM scripts or via the CICE build namelist as follows CODEROOT ice cice bld build namelist config config_cache xml csmdata DIN_LOC_ROOT infile ccsm_namelist inputdata CASEBUILD cice input_data_list A namelist amp cice CICE_NAMELIST_OPTS stream_fldfilename CESMSSTFN stream_domfilename CESMSSTFN stream_year_first DOCN_SSTDATA_YEAR_START stream_year_last DOCN_SSTDATA_YEAR_END model_year_align DOCN_SSTDATA_YEAR_START stream_fldvarname ice_cov exit 1
20. e not computed and ice is not transported Since the initial ice velocities are read in from the restart file the maximum and minimum velocities written to the log file will be non zero in this case but they are not used in any calculations The value of kstrength determines which formulation is used to calculate the strength of the pack ice The Hibler 1979 calculation depends on mean ice thickness and open water fraction The calculation of Rothrock 1975 is based on energetics and should not be used if the ice that participates in ridging is not well resolved evp_damping is used to control the damping of elastic waves in the ice dynamics It is typically set to true for high resolution simulations where the elastic waves are not sufficiently damped out in a small timestep without a significant amount of subcycling This procedure works by reducing the effective ice strength that s used by the dynamics and is not a supported option advection determines the horizontal transport scheme used The default scheme is the incremental remapping method Lipscomb and Hunke 2004 This method is less diffusive and is computationally efficient for large numbers of categories or tracers The upwind scheme is also available The upwind scheme is only first order accurate The base values of the snow and ice albedos for the CESM3 shortwave option are set in the namelist The ice albedos are those for ice thicker than ahmax which is currently set at 0 5 m
21. ed instantaneous or time averaged output are also generated during a run These are described below 9 1 Stdout Output Diagnostics from the ice model are written to an ASCII file that contains information from the compilation a record of the input parameters and how hemispherically averaged maximum and minimum values are evolving with the integration Certain error conditions detected within the ice setup script or the ice model will also appear in this file Upon the completion of the simulation some timing information will appear at the bottom of the file The file name is of the form ice log LID where LID is a timestamp for the file ID It resides in the executable directory The frequency of the diagnostics is determined by the namelist parameter diagfreq Other diagnostic messages appear in the ccsm log LID or cpl log LID files in the executable directory See the CESM scripts documentation 15 9 2 Restart Files Restart files contain all of the initial condition information necessary to restart from a previous simulation These files are in a standard netCDF 64 bit binary format A restart file is not necessary for an initial run but is highly recommended The initial conditions that are internal to the ice model produce an unrealistic ice cover that an uncoupled ice model will correct in several years The initial conditions from a restart file are created from an equilibrium solution and provide more realistic information that is ne
22. emap incremental remapping upwind first order advection shortwave Character dEdd Shortwave Radiative Transfer Scheme default CESM3 Shortwave dEdd delta Eddington Shortwave albicev Double 0 73 Visible ice albedo CESM3 albicei Double 0 33 Near infrared ice albedo CESM3 albsnowv Double 0 96 Visible snow albedo CESM3 albsnowi Double 0 68 Near infrared snow albedo CESM3 R_ice Double 0 0 Base ice grain radius tuning parameter dEdd R_pnd Double 1 5 Base snow grain radius tuning parameter dEdd R_snw Double 0 0 Base pond grain radius tuning parameter dEdd dT_mlt_in Double 1 5 Snow melt onset temperature parameter dEdd rsnw_mlt_in Double 1500 0 Snow melt maximum radius dEdd Table 4 Namelist Variables for Tracers Varible Type Default Value Description tr_iage Logical true Ice age passive tracer tr_FY Logical true First year ice area passive tracer tr_lvl Logical false Level ice area passive tracer tr_pond Logical true Melt pond physics and tracer tr_aero Logical true Aerosol physics and tracer category as a delta function Bitz et al 2001 This method can leave some categories mostly empty at any given time and cause jumps in the properties of g h kdyn determines the ice dynamics used in the model The default is the elastic viscous plastic EVP dynamics Hunke and Dukowicz 1997 If kdyn is set to o 0 the ice dynamics is inactive In this case ice velocities ar
23. freq Integer histfreq Character Array histfreq_n Integer hist_avg Logical pointer file Character 1cdf64 Logical default 24 m x x x x 1 1 1 1 1 true rpointer ice false Filename for initial and branch runs default uses default initialization none initializes with no ice Times to loop through sub cycle ice dy namics Frequency of diagnostics written min max hemispheric sums to standard out put 24 gt writes once every 24 timesteps 1 gt diagnostics written each timestep 0 gt no diagnostics written Frequency of output written to history streams D or d writes daily data W or w writes weekly data M or m writes monthly data Y or y writes yearly data 1 writes every timestep x no history data is written Frequency history data is written to each stream If true averaged history information is written out at a frequency determined by histfreq If false instantaneous values rather than time averages are written Pointer file that contains the name of the restart file Use 64 bit offset in netcdf files Table 2 Maximum values for ice model timestep dt Maximum values for dt for the two standard CESM POP grids assuming max u v 0 5m s are shown in Table 2 The default timestep for CICE is 30 minutes which must be equal to the coupling interval set Grid min Az Ay ma
24. h data are written to a history file as well as the interval over which the time average is to be performed is controlled by the namelist variable histfreq Data averaging is invoked by the namelist variable hist_avg The averages are constructed by accumulating the running sums of all variables in memory at each timestep The options for both of these variables are described in Table 1 If hist_avg is true and histfreq is set to monthly for example monthly averaged data is written out on the last day of the month 17 Table 9 Time and Grid Information Written to History File Field Description Units time model time days time_bounds boundaries for time averaging interval days TLON T grid center longitude degrees TLAT T grid center latitude degrees ULON U grid center longitude degrees ULAT U grid center latitude degrees tmask ocean grid mask 0 land 1 ocean tarea T grid cell area m uarea U grid cell area m dxt T cell width through middle m dyt T cell height through middle m dxu U cell width through middle m dyu U cell height through middle m HTN T cell width North side m HTE T cell width East side m ANGLET angle grid makes with latitude line on T grid radians ANGLE angle grid makes with latitude line on U grid radians ice_present fraction of time averaging interval that any ice is present 9 3 3 Changing Content The second namelist in the setup script controls what variables are written to the history file To
25. he ice model namelist are described in section 3 2 2 The Build Environment The build and configure environment has changed significantly from previous versions of CESM The build namelist and configure utilities are based on the CAM scripts The configure utility includes setting compile time parameters such as the horizontal grid the sea ice mode prognostic or prescribed tracers etc Additional options can be set using the configure utility such as the decomposition and the number of tasks but these are typically set via CESM enviroment variables However the CAM scripts set some of these explicitly through the configure command line For example one such configure line in the CESM scripts is H A Se E m AS Invoke cice configure PE oe NE E E ea Se a a A a ee Se set hgrid hgrid ICE_GRID if ICE_GRID Tx set hgrid hgrid ICE_NX x ICE_NY set mode cice_mode CICE_MODE cd CASEBUILD ciceconf exit 1 CODEROOT ice cice bld configure hgrid mode nodecomp CICE_CONFIG_OPTS exit 1 This example sets the horizontal grid and the mode prognostic or prescribed The build namelist utility sets up the namelist which controls the run time options for the CICE model This utility sets namelist flags based on compile time settings from configure and some standard defaults based on horizontal grids and other options The typical execution during the CESM configure is CODEROOT ice cice bld build namelist
26. ice option along with the history namelist variables are set in ice_prescribed F90 and ice_history F90 respectively If they are not set in the namelist in the script they will assume the default values listed in Tables 1 8 which list all available namelist parameters The default values shown here are for the coupled model which is set up for a production run Only a few of these variables are required to be set in the namelist these values are noted in the paragraphs below An example of the default namelist is shown in Section 3 9 1 The main run management namelist options are shown in Table 1 While additional namelist variables are available in the uncoupled version they are set by the driver in CESM Variables set by the driver include dt runid runtype istep0 days_per_year restart and dumpfreq These should be changed in the CESM configuration files CESM scripts http www cesm ucar edu models cesm1 0 cesm_doc book1 html 3 1 Changing the timestep dt is the timestep in seconds for the ice model thermodynamics The thermodynamics component is stable but not necessarily accurate for any value of the timestep The value chosen for dt depends on the stability of the transport and the grid resolution A conservative estimate of dt for the transport using the upwind advection scheme is Table 1 Namelist Variables for Run Management Varible Type Default Value Description ice_ic character xndt_dyn Integer diag
27. nformation are written to every file and are listed in Table 9 In addition to the history files a netCDF file containing a snapshot of the initial ice state can be created at the start of each run The file name is CASE cice i yyyy mm dd sssss nc and is written in the executable directory 16 9 3 1 Caveats Regarding Averaged Fields In computing the monthly averages for output to the history files most arrays are zeroed out before being filled with data These zeros are included in the monthly averages where there is no ice For some fileds this is not a problem for example ice thickness and ice area For other fields this will result in values that are not representative of the field when ice is present Some of the fields affected are e Flat Fsens latent and sensible heat fluxes e evap evaporative water flux e Fhnet ice ocn net heat flux e Fswabs snow ice ocn absorbed solar flux e strairx strairy zonal and meridional atm ice stress e strcorx strcory zonal and meridional coriolis stress For some fields a non zero value is set where there is no ice For example Tsfc has the freezing point averaged in and Flwout has oT averaged in At lower latitudes these values can be erroneous To aid in the interpretation of the fields a field called ce_present is written to the history file It contains information on the fraction of the time averaging interval when any ice was present in the grid cell during the time aver
28. put Data 9 1 Stdout Output id 2 Gee EE RAD RG ieee ead eee Bees Oi Restart I EE E te es at ate ME tthe Ui Ghai aol NM gute Mae seats AS e edie ie Mae gh ot 939 History Biless SAI BS ye A A AL be oh ed ed Ae Roth Me Bete Aa A 9 3 1 Caveats Regarding Averaged Fields 0 oo e eee 9 3 2 Changing Frequency and Averaging e 9 3 3 Changing Content iua oko a E AGS A oer hh e a ja 10 Troubleshooting 10 1 Code does not Compile or Run ee 10 2 Negative Ice Area in Horizontal Remapping e 10 3 Thermodynamic Iteration ErTOr 10 4 Cons rvation Error i eaea do e de A pa O A RLS A 10 5 NX does not divide evenly into grid o e e 10 6 Enabling the Debugger ee 14 14 14 1 Introduction This User s Guide accompanies the CESM1 User s Guide and is intended for those who would like to run CICE coupled on a supported platform and out of the box Users running CICE fully coupled should first look at the CESM1 User s Guide http www cesm ucar edu models cesm1 0 cesm_doc book1 html It includes a quick start guide for downloading the CESM1 source code and input datasets and informa tion on how to configure build and run the model The supported configurations and scripts for building the fully coupled model are also described in the CESM1 User s Guide The CICE User s Guide is intended for users interested in making modifications to the ice
29. remove a field from this list add the name of the character variable associated with that field to the amp icefields_nm1 namelist in cice buildnml csh and assign it a value of xxxxx For example to remove ice thickness and snow cover from the history file add gicefields_nml f_hi UXXXXXx f_hs xxxxx to the namelist Table 10 Standard Fields Available for Output to History File Logical Variable Description Units f hi grid box mean ice thickness m f hs grid box mean snow thickness m f_fs grid box mean snow fraction f_Tsfc snow ice surface temperature C f_aice ice concentration aggregate f_aicel ice concentration category 1 f_aice2 ice concentration category 2 f aice3 ice concentration category 3 f_aice4 ice concentration category 4 f_aice5 ice concentration category 5 f_aice6 ice concentration category 6 f_aice7 ice concentration category 7 continued on next page 18 continued from previous page f_aice8 f_aice9 f_aicel0 f vicel f vice2 f_vice3 f_vice4 f_viceb f_vice6 f_vice7 f_vice8 f_vice9 f_vicel0 f_uvel f vvel f_fswdn f_flwdn f_snow f_snow_ai f rain f rain ai f_sst f_sss f_uocn f_vocn f_frzmlt f_fswabs f_fswabs_ai f_aldvr f_aldvi f_flat f_flat_ai f_fsens f_fsens_ai f_flwout f_flwout_ai f_evap f_evap_ai f_Tref f_Qref f_congel f frazil f_snoice f_meltb f_meltt f_meltl f_fresh f_fresh_ai ice concentration categor
30. ry_dir are the directories where the initial condition file the restart files and the history files will be written respectively These values are set at the top of the setup script and have been modified from the default values to meet the requirements of the CESM filenaming convention This allows each type of output file to be written to a separate directory If the default values are used all of the output files will be written to the executable directory incond_file dump_file and history_file are the root filenames for the initial condition file the restart files and the history files respectively These strings have been determined by the requirements of the CESM filenaming convention so the default values are set by the CESM driver See 9 2 and 9 3 for an explanation of how the rest of the filename is created 3 3 Model Physics The namelist variables for the ice model physics are listed in Table 3 restart is almost always true since most run types begin by reading in a binary restart file See section 5 for a description of the run types and about using restart files and internally generated model data as initial conditions kcolumn is a flag that will run the model as a single column if is set to 1 This option has not been thoroughly tested and is not supported The calculation of the ice velocities is subcycled ndte times per timestep so that the elastic waves are damped before the next timestep The subcycling timestep is calculated
31. ry_type processor_shape amp ice_prescribed_nml prescribed_ice remap default 0 45 0 75 0 73 0 98 false gt dEdd cartesian yclic open square pop false 3 9 2 Example 2 History File Namelist The second namelist controls what variables are written to the history file By default all files are written to the history file Variables that are not output are set in the namelist icefields_nml Some of the following fields are not written to the history file since they can be retrieved from the ocean history files The melt and freeze onset fields are not used since the information they contain may not be correct if the model is restarted mid year The ice areas and volumes for categories six through ten are not used since the default thickness distribution consists of five ice categories f_aero mxxxx f_aicen f_aisnap f_apondn f_congel f_daidtd f_daidtt f_divu gt mxXxxx f_dvidtd f_dvidtt f_faero_atm MXXXX gt mdxxx gt mxxXxx MXXXX MXXXX MXXXX MXXXX MXXXX MXXXX 12 f_faero_ocn mxxxx f_fhocn mxxxx f_fhocn_ai mxxxx f_frazil mxxxx f_fresh mxxxx f_fresh_ai mxxxx f_frz_onset XxXxXxx f_frzmlt XXXXXx f_fsalt mxxxx f_fsalt_ai mxxxx f_fy mdxxx f_hisnap mdxxx f_icepresent MXXXX f_meltb mxxxx f_meltl
32. s lt OS gt file for your platform Modify the directory paths for the libraries e Make sure all paths and file names are set correctly in the scripts e If changes were made to the ice_model_size F90 file in the source code directory they will be over written by the file in input_templates 10 2 Negative Ice Area in Horizontal Remapping This error is written from ice_transport_remap F90 when the ice model is checking for negative ice areas If it happens well into a model integration it can be indicative of a CFL violation The output looks like 60 New area lt 0 istep 119588 60 my_task i j n 4 21 380 1 60 Old area 60 New area 0 960675000975677174E 05 0 161808948357841311E 06 20 2 N fata R Ma a R ten e iodo a a ZZZZZZZBEBZZ E BB B B BB l NX aa 2 k day day day cm day cm day 1 60 Net flux 0 976855895811461324E 05 60 shr_sys_abort ERROR remap transport negative area 60 shr_sys_abort WARNING calling shr_mpi_abort and stopping 60 shr_mpi_abort remap transport negative area 0 The dynamics timestep should be reduced to integrate past this problem Set xndt_dyn 2 in the namelist and restart the model When the job completes set the value back to 1 10 3 Thermodynamic Iteration Error This error is written from ice_therm_vertical F90 when the ice model temperature iteration is not con verging in the thermo
33. sport scheme is no longer supported in CICE4 The upwind advection scheme is the only additional option and is contained in ice_transport_driver F90 e The standalone ice model is now only available through Los Alamos National Laboratory e Several physics options have been shifted around into other or new modules For example most of ice_albedo F90 is now in ice_shortwave F90 The new module contains all of the shortwave radiative transfer plus the basic albedo calculations e The mechanical redistribution scheme has been changed significantly and is available in ice_mechred F90 e A new drivers area has been created for modules that are specific to the CESM as opposed to the standalone CICE model The new CESM drivers are contained in the cpl_mct and cpl_share subdirec tories The ESMF driver cpl_esmf is still under development The source subdirectory now contains driver independent source code for the most part e A new bld subdirectory has been introduced which contains CESM specific build and configure scripts These scripts handle the namelist generation defaults and configuration details The CICE source code is based on the Los Alamos sea ice model CICE model version 4 The main source code is very similar in both versions but the drivers are significantly different If there are some topics that are not covered in the CICE documentation users are encouraged to look at the CICE documentation Hunke and Lipscomb 2008 It is avail
34. story streams currently set to a maximum of 5 The namelist variables histfreq and histfreq_n are now arrays which allow for different frequency history file sets More detail on this is available in 9 3 The namelist variable pointer_file is set to the name of the pointer file containing the restart file name that will be read when model execution begins The pointer file resides in the scripts directory and is created initially by the ice setup script but is overwritten every time a new restart file is created It will contain the name of the latest restart file The default filename ice restart_file shown in Table 1 will not work unless some modifications are made to the ice setup script and a file is created with this name and contains the name of a valid restart file this variable must be set in the namelist More information on restart pointer files can be found in section 9 2 The variables dumpfreq and dumpfreq _n control the output frequency of the netCDF restart files writing one restart file per year is the default and is set by the CESM driver The default format for restart files is now netCDF but this can be changed to binary through the namelist variable restart _format If print_points is true diagnostic data is printed out for two grid points one near the north pole and one near the Weddell Sea The points are set via namelist variables latpnt and lonpnt This option can be helpful for debugging incond_dir restart_dir and histo
35. tup script and print an error message to the ice bldlog build log file The flag DMXBLCKS is essentially the threading option This controls the number of blocks per proces sor This can describe the number of OpenMP threads on an MPI task or can simply be that a single MPI task handles a number of blocks The flat DNTR_AERO n flag turns on the aerosol deposition physics in the sea ice where n is the number of tracer species and O turns off the tracers More details on this are in the section on tracers The flag D_MPI sets up the message passing interface This must be set for runs using a parallel environment To get a better idea of what code is included or excluded at compile time grep for ifdef and ifndef in the source code or look at the f90 files in the obj directory 3 Namelist Variables CICE uses the same namelists for both the coupled and uncoupled models This section describes the namelist variables in the namelist ice_nml which determine time management output frequency model physics and filenames The ice namelists for the coupled model are now located in CASE Buildconf A script reads the input namelist at runtime and writes the namelist information to the file ice_in in the directory where the model executable is located Therefore the namelist will be updated even if the ice model is not recompiled The default values of the ice setup grid tracer and physics namelists are set in ice_init F90 The prescribed
36. ut access to these computer resources The physics in the uncoupled ice model are identical to those in the ice model used in the fully coupled system CICE is a dynamic thermodynamic model that includes a subgrid scale ice thickness distribution Bitz et al 2001 Lipscomb 2001 It uses the energy conserving thermodynamics of Bitz and Lipscomb 1999 has multiple layers in each thickness category and accounts for the influences of brine pockets within the ice cover The ice dynamics utilizes the elastic viscous plastic EVP rheology of Hunke and Dukowicz 1997 Sea ice ridging follows Rothrock 1975 and Thorndike et al 1975 A slab ocean mixed layer model is included A Scientific Reference is available that contains more detailed information on the model physics An attempt has been made throughout this document to provide the following text convention Variable names used in the code are typewritten Subroutine names are given in italic and file names are in boldface 1 1 What s new in CICE4 CICE4 is an upgraded version of the Community Sea Ice Model CSIM5 which was based on CICE3 and was released in June 2004 The model physics are similar to that of CSIM5 but it was decided to move to CICE the LANL sea ice model for practical reasons The major changes are e The incremental remapping transport scheme is now the default and is available in the modules called ice_transport_driver F90 and ice_transport_remap F90 The MPDATA tran
37. xAt gx3vo 28845 9 m 4 0 hr gxlv3 8558 2 m 1 2 hr min Ax Ay At lt in the CESM configuration files Occasionally ice velocities are calculated that are larger than what is assumed when the model timestep 4max u v 1 is chosen This causes a CFL violation in the transport scheme A namelist option was added xndt_dyn to subcycle the dynamics to get through these instabilities that arise during long integrations The default value for this variable is one and is typically increased to two when the ice model reaches an instability The value in the namelist should be returned to one by the user when the model integrates past that point 3 2 Writing Output The namelist variables that control the frequency of the model diagnostics netCDF history and restart files are shown in Table 1 By default diagnostics are written out once every 48 timesteps to the ascii file ice log LID see section 9 1 LID is a time stamp that is set in the main script The namelist variable histfreq controls the output frequency of the netCDF history files writing monthly averages is the default The content of the history files is described in section 9 3 The value of hist_avg determines if instantaneous or averaged variables are written at the frequency set by histfreq If histfreq is set to 1 for instantaneous output hist_avg is set to false within the source code to avoid conflicts The latest version of CICE allows for multiple hi
38. y 8 ice concentration category 9 ice concentration category 10 ice volume category 1 ice volume category 2 ice volume category 3 ice volume category 4 ice volume category 5 ice volume category 6 ice volume category 7 ice volume category 8 ice volume category 9 ice volume category 10 zonal ice velocity meridional ice velocity downwelling solar flux downwelling longwave flux snow fall rate received from coupler snow fall rate on ice cover rain fall rate received from coupler rain fall rate on ice cover sea surface temperature sea surface salinity zonal ocean current meridional ocean current freeze melt potential absorbed solar flux sent to coupler absorbed solar flux in snow ocn ice visible direct albedo near infrared direct albedo latent heat flux sent to coupler ice atm latent heat flux sensible heat flux sent to coupler ice atm sensible heat flux outgoing longwave flux sent to coupler ice atm outgoing longwave flux evaporative water flux sent to coupler ice atm evaporative water flux 2 m reference temperature 2 m reference specific humidity basal ice growth frazil ice growth snow ice formation basal ice melt surface ice melt lateral ice melt ice ocn fresh water flux sent to coupler ice ocn fresh water flux EBBBBBBBES XXX cm day cm day g kg cm day cm day cm day cm day cm day cm day cm day cm day continued on next page
39. y maintained by the setup script and the component model 9 3 History Files History files contain gridded data values written at specified times during a model run By default the history files will be written to the directory history_dir defined in the namelist The netCDF file names are prepended by the character string given by history _file in the ice _nml namelist This character string has been set according to CESM Output Filename Requirements If history_file is not set in the namelist the default character string iceh is used The user can specify the frequency at which the data are written Options are also available to record averaged or instantaneous data The form of the history file names are as follows Yearly averaged CASE cice h yyyy nc Monthly averaged CASE cice h yyyy mm nc Daily averaged CASE cice h yyyy mm dd nc Instantaneous histfreq y m or d CASE cice h yyyy mm dd sssss nc Instantaneous written every dt histfreq 1 CASE cice h yyyy mm dd sssss nc CASE is set in the main setup script Note that the denotes the multiple stream option where the first stream is just h and subsequent streams are hi h2 etc All history files are written in the executable directory Changes to the frequency and averaging will affect all output fields The best description of the history data comes from the file itself using the netCDF command ncdump h filename nc Variables containing grid i
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