Title: ARCMIP EASE-Grid model data Author: John Allison NCAR/EOL jja@ucar.edu +1-303-497-2633 Contact: UCAR/EOL PO Box 3000 Boulder CO 80307-3000 USA +1-303-497-8987 codiac@ucar.edu http://data.eol.ucar.edu/codiac_data/arcmip/docs/regrid/ Data set overview: Model data from participating ARCMIP modelers were re-gridded to fit the ARCMIP EASE-Grid. The ARCMIP EASE-Grid is a 50km equal area grid on a northern azimuthal projection, i.e. a 50km version of the original NL/NH grids for SSM/I described at the EASE-Grid webpage. < http://nsidc.org/data/ease/ease_grid.html > Call this "N5": a 50km grid for the entire hemisphere, which is a 361x361 grid (130321 cells). A rectangle on this grid was fit around the ARCMIP 70x55 domain.txt grid < http://cires.colorado.edu/lynch/arcmip/domain.html >, and a 5 cell (250km) border was added to define the ARCMIP EASE-Grid. The center of the new grid is 72N 153W, consisting of N5 columns 113-212 and rows 101-192 (100x92 = 9200 cells). The latlons of the corners of the ARCMIP EASE-Grid are: where col row lat lon upper left 113 101 41.89710 -139.69868 upper right 212 101 50.81162 157.94894 lower left 113 192 58.93256 -79.84573 lower right 212 191 74.54461 69.44396 ARCMIP EASE-Grid cells are calculated using up to the 4 closest model points [*] in a linear distance-weighted average to determine the value for each and every ARCMIP EASE-Grid cell. To avoid a significant edge effect where the 4 closest model points are quite far away, model points are not used if they are more than 50km away. Thus much of the EASE-Grid data is set to a missing value. [*] The model data may be created as grid cells, but during interpolation to the new grid, the data values are taken as point data located at the latlon associated with that cell. Presumably the latlon provided by the model is the center of that model grid cell. The linear distance-weighted average equation used: v0 is the ARCMIP EASE-Grid cell variable value v1,v2,v3,v4 are the model variable values at the 4 closest model points d1,d2,d3,d4 are the distances from the center of the EASE cell to the model point d4 is the furthest away num = v1 * d4/d1 + v2 * d4/d2 + v3 * d4/d3 + v4 * d4/d4 den = d4/d1 + d4/d2 + d4/d3 + d4/d4 v0 = num / den Terms drop out when dn>50km and a new furthest is determined. Data format: Data are stored in netCDF files similar in format to that described in the ARCMIP data archive document available at: < http://paos.colorado.edu/~curryja/arcmip/arcmip_data.pdf > The iew and jns indices have been changed to col and row since directional specifications are confusing on this grid. Original model domain latlons are in files named of the form "model_run_domain.nc". All original model documentation is also included, either as "model_run_*.txt" in the top-level model directory or "README*" in the appropriate subdirectory. In the "ease.tar.gz" file are all EASE-Gridded data, one for each of the model's daily "may" files, and for each of the monthly ("mon") files. Also included is the file "ease_domain.nc", containing latitudes and longitudes for the ARCMIP EASE-Grid (this is the same for every model). The file "model_run_distance.nc" contains the model indices of the 4 closest points to the EASE-Grid cell and their distances from the center of the EASE-Grid cell. These are the candidate points for interpolation (subject to the 50km maximum described above). The "may.tar.gz" and "mon.tar.gz" files contain the model's original data files for the May 1998 and each of the monthly files, respectively. The "col.tar.gz" file contains the model's column files in their original form. No processing to the EASE-Grid was performed. The data for each model are on one tape, with the two calibration datasets on another tape, one file per dataset. On the models tape: README_ease.txt, arcsym, coamps, hirham, narcm, smhirc. On the calibration tape: README_ease.txt, caspr, isccp. Each file is in the Unix tar format, containing metadata and data files in .tar.gz form as described above. The caspr and isccp files differ slightly in organization, but also contain .tar.gz files of the data. In addition, the models tape includes a 7th file (file #6), containing the HTML and associated files for the EOL ARCMIP Regridding Project website, and the EOL regridding software source code, plus other reference source code. Example, to retrieve just the HIRHAM EASE-Grid files, use the standard Unix commands to skip the first 3 files and then un-tar the "ease" tarball from the "hirham" file: % mkdir hirham % cd hirham % mt -f /dev/rmt/0n rewind % mt -f /dev/rmt/0n fsf 3 % tar xvf /dev/rmt/0n hirham_hi02_ease.tar.gz % gzcat hirham_hi02_ease.tar.gz | tar xvf - A complete listing of the tape contents is appended below. References: ARCMIP home page http://curry.eas.gatech.edu/ARCMIP/ EASE-Grid details http://nsidc.org/data/ease/ease_grid.html Appendix: tape contents (with file size on disk- size on tape will differ due to blocking) Each file on the tape is a Unix tar file. Tape 1: models tape file 0: README_ease.txt (this file) 11288 file 1 (arcsym): arcsym_ar05_col.tar.gz 16595425 arcsym_ar05_domain.nc 47156 arcsym_ar05_ease.tar.gz 459420227 arcsym_ar05_may.tar.gz 349007077 arcsym_ar05_metadata.txt 2121 arcsym_ar05_mon.tar.gz 22091743 md5.txt 386 md5sum.txt 344 file 2 (coamps): COAMPS_0001_col.tar.gz 22689551 COAMPS_0001_domain.nc 1016908 COAMPS_0001_ease.tar.gz 837513306 COAMPS_0001_may.tar.gz 392753301 COAMPS_0001_metadata.txt 777 COAMPS_0001_mon.tar.gz 33141463 md5.txt 386 md5sum.txt 344 file 3 (hirham): hirham_hi02_col.tar.gz 13398856 hirham_hi02_domain.nc 42932 hirham_hi02_ease.tar.gz 541033488 hirham_hi02_may.tar.gz 382373181 hirham_hi02_metadata.txt 1466 hirham_hi02_mon.tar.gz 21976887 md5.txt 386 md5sum.txt 344 file 4 (narcm): md5.txt 386 md5sum.txt 344 narcm2_ar01_col.tar.gz 258129061 narcm2_ar01_domain.nc 47156 narcm2_ar01_ease.tar.gz 185988284 narcm2_ar01_may.tar.gz 73008655 narcm2_ar01_metadata.txt 1727 narcm2_ar01_mon.tar.gz 4705497 file 5 (smhirc): md5.txt 386 md5sum.txt 344 smhirc_4223_col.tar.gz 12780357 smhirc_4223_domain.nc 75284 smhirc_4223_ease.tar.gz 604574448 smhirc_4223_may.tar.gz 331329525 smhirc_4223_metadata.txt 974 smhirc_4223_mon.tar.gz 18837945 file 6: html/ 543744 src/ 23643136 Tape 2: calibration tape file 0: README_ease.txt (this file) 11288 file 1 (caspr): CASPR.Readme 7059 caspr_199701.easegrid.tar.gz 59164781 caspr_199702.easegrid.tar.gz 56651010 caspr_199703.easegrid.tar.gz 64866164 caspr_199704.easegrid.tar.gz 64917650 caspr_199705.easegrid.tar.gz 70249219 caspr_199706.easegrid.tar.gz 69840538 caspr_199707.easegrid.tar.gz 71678697 caspr_199708.easegrid.tar.gz 68978990 caspr_199709.easegrid.tar.gz 64070065 caspr_199710.easegrid.tar.gz 64595491 caspr_199711.easegrid.tar.gz 58157249 caspr_199712.easegrid.tar.gz 57629903 caspr_199801.easegrid.tar.gz 58919143 caspr_199802.easegrid.tar.gz 56451955 caspr_199803.easegrid.tar.gz 63844112 caspr_199804.easegrid.tar.gz 64869045 caspr_199805.easegrid.tar.gz 71275337 caspr_199806.easegrid.tar.gz 71421138 caspr_199807.easegrid.tar.gz 72124805 caspr_199808.easegrid.tar.gz 70064728 caspr_199809.easegrid.tar.gz 64807045 caspr_199810.easegrid.tar.gz 64209356 caspr_199811.easegrid.tar.gz 57386154 caspr_199812.easegrid.tar.gz 56498217 caspr_easegrid_position.nc.gz 118129 map_tools_isccp.nc.gz 98909 md5.txt 1868 md5sum.txt 1679 file 2 (isccp): ISCCP.Readme 7404 isccp_9709.NOA.tar.gz 34049941 isccp_9709.NOM.tar.gz 34649477 isccp_9710.NOA.tar.gz 32532589 isccp_9710.NOM.tar.gz 31133276 isccp_9711.NOM.tar.gz 27014628 isccp_9712.NOA.tar.gz 28423221 isccp_9712.NOM.tar.gz 26860841 isccp_9801.NOA.tar.gz 28703730 isccp_9801.NOM.tar.gz 27007214 isccp_9802.NOA.tar.gz 28012687 isccp_9802.NOM.tar.gz 26073300 isccp_9803.NOA.tar.gz 34356813 isccp_9803.NOM.tar.gz 33647423 isccp_9804.NOA.tar.gz 35271717 isccp_9804.NOM.tar.gz 35933729 isccp_9805.NOA.tar.gz 37626464 isccp_9805.NOM.tar.gz 37667167 isccp_9806.NOA.tar.gz 37162713 isccp_9806.NOM.tar.gz 36922789 isccp_9807.NOA.tar.gz 37917838 isccp_9807.NOM.tar.gz 37662471 isccp_9808.NOA.tar.gz 37267473 isccp_9808.NOM.tar.gz 37328092 isccp_9809.NOA.tar.gz 34125032 isccp_9809.NOM.tar.gz 34015286 isccp_alb.NOA.nc.gz 23207272 isccp_alb.NOM.nc.gz 24242073 isccp_cbpr.NOA.nc.gz 29401910 isccp_cbpr.NOM.nc.gz 32513231 isccp_ctpr.NOA.nc.gz 33567092 isccp_ctpr.NOM.nc.gz 35084943 isccp_lwds.NOA.nc.gz 41201623 isccp_lwds.NOM.nc.gz 43300967 isccp_lwus.NOA.nc.gz 41875207 isccp_lwus.NOM.nc.gz 43921472 isccp_lwut.NOA.nc.gz 40855685 isccp_lwut.NOM.nc.gz 42912497 isccp_o3.NOA.nc.gz 18021017 isccp_o3.NOM.nc.gz 18927365 isccp_pwc.NOA.nc.gz 35877137 isccp_pwc.NOM.nc.gz 37795817 isccp_skin.NOA.nc.gz 35485312 isccp_skin.NOM.nc.gz 37192948 isccp_swds.NOA.nc.gz 17971147 isccp_swds.NOM.nc.gz 19231134 isccp_swdt.NOA.nc.gz 18186216 isccp_swdt.NOM.nc.gz 19505419 isccp_swus.NOA.nc.gz 16172019 isccp_swus.NOM.nc.gz 17201451 isccp_swut.NOA.nc.gz 17921911 isccp_swut.NOM.nc.gz 19084670 isccp_tau.NOA.nc.gz 28633341 isccp_tau.NOM.nc.gz 26891276 map_tools_isccp.nc.gz 98909 md5.txt 3418 md5sum.txt 3033