README_asc [NOTE: The following description applies to the data at its original resolution (360x180). If you have asked for data on a different grid, the string "360x180" will be replaced by a different resolution (e.g., "T42" or "96x48").] The AMIP 2 boundary condition data are to be used in simulations as described in the document on the web: http://www-pcmdi.llnl.gov/projects/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 http://www-pcmdi.llnl.gov/publications/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 sst_bcs_asc_360x180_187001-189012.tar.gz). Then you should extract the individual files from the tar files (e.g., tar xvf sst_bcs_asc_360x180_187001-189012.tar). The following describes how to read the SST boundary condition files you have extracted (for the years 1870-1890); 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.asc contains boundary condition data (mid-month values) for January - December 1870. amipbc_sst_360x180_1871.asc contains boundary condition data (mid-month values) for January - December 1871. . . . amipbc_sst_360x180_1890.asc contains boundary condition data (mid-month values) for January - December 1890. Along with the 8 tarred and zipped files, you will also find a few other files similar to the following: amipbc_sst_360x180_1987-2006_clim.asc contains boundary condition data based on the observed climatology computed for the period: January 1987 - December 2006. 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 ascii files *********** The first 17 lines of each file describe what is in the file, including grid information and the months that are stored. For example, the first 19 lines of a file containing data on a 1x1 degree grid (amipbc_sst_1x1_1999.asc) includes 17 lines of header information and 2 lines of data, as listed here: tosbcs AMIP Boundary Condition Data: Mid-Month SST (K) See: http://www-pcmdi.llnl.gov/amip2/AMIP2EXPDSN/BCS/amip2bcs.html K pcmdi obs 1x1 uniform 360 = number of longitudes 180 = number of latitudes 0.5000 = first longitude 359.5000 = last longitude -89.5000 = first latitude 89.5000 = last latitude 2001 - 2001 = years written 1 = first month (jan, feb, mar, ... = 1, 2, 3, ...) 12 = last month (jan, feb, mar, ... = 1, 2, 3, ...) 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 271.360 The following FORTRAN code segment can be used to read the data in any of the 1x1 degree SST and seaice boundary condition files: real dat(360,180,12) integer i, j, m, mon1, monn c NOTE: to read a different file, replace the following with the c correct file name open(10, file='amipbc_sst_1x1_1999.asc', status='old') read(10, '(13(/))') read(10, '(i5)') mon1 read(10, '(i5)') monn read(10, '(1x)') read(10,'(10f8.3)') & (((dat(i,j,m), i=1,360), j=1,180), m=mon1,monn) close(10) Note that the data are stored with longitude as the first dimension, latitude the second, and month the last dimension. The longitudes are stored from west to east starting at longitude 0.5 degrees east. The latitudes are stored from south to north starting at 89.5 degrees south. The months are stored with time increasing, with m=1 corresponding to January, m=2 corresponding to February, ...., m=12 corresponding to December. Most files contain a full year of data (January through December). For files with data only for part of the year, the above code would not fully fill the array "dat". For sea ice percentage, the format in the last read should be changed to '(10f8.2)'. *********** end ascii files ***********