README_nc

The AMIP 2 boundary condition data are to be used in simulations as
described in the document on the web: 
https://pcmdi.llnl.gov/mips/amip/AMIP2EXPDSN/BCS/amip2bcs.html.  
This document has also been published as a PCMDI report:  Taylor, K.E., 
D. Williamson and F. Zwiers, 2000: "The sea surface temperature and sea
ice concentration boundary conditions for AMIP II simulations," PCMDI
Report No. 60, Program for Climate Model Diagnosis and Intercomparison,
Lawrence Livermore National Laboratory, 25 pp (available at
https://pcmdi.llnl.gov/report/ab60.html). These boundary
condition data sets are based on, but not the same as, the monthly mean
data. 

There are a few uncompressed files and 8 compressed tar files:  half 
the compressed files contain boundary condition data (the "bcs" files --
YOU SHOULD USE THE "BCS" FILES IN DRIVING YOUR MODEL SIMULATIONS); 
the other half contain observed monthly mean data (the "obs" files,
which you can use after you run your model to see that you recover 
the observed values).  

First you should uncompress the files
(e.g., gunzip amipbcs_tos_1870-1899.tar.gz).  Then you should
extract the individual files from the tar files (e.g., tar xvf
sst_bcs_nc_360x180_187001-189012.tar).  The following describes how to read
the SST boundary condition  files you have extracted (for the years 
1870-1899); a similar procedure applies for the later time-periods and 
also for the sea ice concentration files, as well as the observed monthly
mean data.

The SST and seaice data have been extrapolated to cover the entire globe, 
but note that you shouldn't trust it over land regions or inland seas and 
lakes.

Upon completing the "gunzip" and "tar" steps, you should have
access to the following files containing sea surface temperature (SST)
data:

  amipbc_sst_360x180_1870.nc   contains boundary condition data (mid-month
                                values) for January - December 1870.
  amipbc_sst_360x180_1871.nc   contains boundary condition data (mid-month
                                values) for January - December 1871.
         .
         .
         .

  amipbc_sst_360x180_1899.nc   contains boundary condition data (mid-month
                                values) for January - December 1899.

Along with the 8 tarred and zipped files, you will also find a few other
files similar to the following:


  amipbc_sst_360x180_1988-2007_clim.nc  contains boundary condition data 
                            based on the observed climatology computed for 
                            the period: January 1988 - December 2007.

  bcinfo_sst_360x180.nc   contains some statistical information concerning
                           the boundary condition data, which will not
                           be of general interest.
  
  amipbc_sst_360x180.out       contains the text output documenting the
                           conditions under which the boundary conditions
                           were generated, which will not be of general
                           interest.

***********
begin netCDF files
***********
The ncdump utility can be used to extract the header information from
each file.  For data on a 1x1 degree grid, for example, the result of
the command, "ncdump -h amipbc_sst_360x180_2001.nc", produces the following
listing:

netcdf amipbc_sst_360x180_2001 {
dimensions:
	time = UNLIMITED ; // (12 currently)
	latitude = 180 ;
	bound = 2 ;
	longitude = 360 ;
variables:
	double time(time) ;
		time:units = "days since 1870-1-1" ;
		time:long_name = "time" ;
		time:standard_name = "time" ;
		time:calendar = "gregorian" ;
		time:axis = "T" ;
	double latitude(latitude) ;
		latitude:bounds = "bounds_latitude" ;
		latitude:units = "degrees_north" ;
		latitude:long_name = "Latitude" ;
		latitude:standard_name = "latitude" ;
		latitude:axis = "Y" ;
	double bounds_latitude(latitude, bound) ;
	double longitude(longitude) ;
		longitude:bounds = "bounds_longitude" ;
		longitude:modulo = 360. ;
		longitude:long_name = "Longitude" ;
		longitude:standard_name = "longitude" ;
		longitude:units = "degrees_east" ;
		longitude:topology = "circular" ;
		longitude:axis = "X" ;
	double bounds_longitude(longitude, bound) ;
	float tosbcs(time, latitude, longitude) ;
		tosbcs:name = "tosbcs" ;
		tosbcs:long_name = "AMIP constructed mid-month sea surface temperature" ;
		tosbcs:standard_name = "sea_surface_temperature" ;
		tosbcs:cell_methods = "time: point" ;
		tosbcs:units = "K" ;
		tosbcs:missing_value = 1.e+20f ;

// global attributes:
		:Conventions = "CF-1.6" ;
		:history = "File processed: 22-06-2015 19:58:17 PM UTC; San Francisco, CA, USA" ;
		:host = "oceanonly.llnl.gov; UVCDAT version: 2.2.0; Python version: 2.7.9 (default, May 28 2015, 13:43:07); [GCC 4.4.7 20120313 (Red Hat 4.4.7-11)]" ;
		:comment = "Based on Hurrell SST/sea ice consistency criteria applied to merged HadISST (1870-01 1981-10) & NCEP-0I2 (1981-11 to 2015-03)" ;
		:contact = "pcmdi-cmip@lists.llnl.gov" ;
		:creation_date = "2015-06-22T19:58:17Z" ;
		:data_structure = "grid" ;
		:data_usage_tips = "The mid-month data should be linearly interpolated in time and then clipped for use as boundary conditions to drive AMIP simulations as described at: http://www-pcmdi.llnl.gov/projects/amip/AMIP2EXPDSN/BCS/amip2bcs.php" ;
		:frequency = "mon" ;
		:institute_id = "PCMDI" ;
		:institution = "Program for Climate Model Diagnosis and Intercomparison (LLNL), Livermore, CA, U.S.A." ;
		:mip_specs = "AMIP CMIP5 CMIP6" ;
		:project_id = "AMIP" ;
		:realm = "ocean" ;
		:references = "Taylor, K.E., D. Williamson and F. Zwiers, 2000: The sea surface temperature and sea ice concentration boundary conditions for AMIP II simulations. PCMDI Report 60, Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, 25 pp. Available online: http://www-pcmdi.llnl.gov/publications/pdf/60.pdf" ;
		:source = "Merged SST based on UK MetOffice HadISST and NCEP OI2" ;
		:source_id = "PCMDI-AMIP-1.0.0" ;
}