This directory contains reference material and files for use by the Measures snow and ice product team. See longer sections for details on each category 1) Example NCL script and netCDF-CF file. 2) Land/Ocean/Ice-masks for EASE2_N25km and EASE2_N100km 3) lat/lon grid arrays for EASE2_N25km and EASE2_N100km 4) Link to QC summary white paper describing regridding issues encountered in 1994, during development of the Combined Snow and Ice data set at NSIDC. 5) mapx libary for OSX and idl_grids library to tie IDL to full mapx functionality. ************************************************************************ 1) Example NCL script and netCDF-CF file. The script is an NCAR Command Language script I used to produce CF-compliant data in the sample file. The tricky piece was that netCDF files usually assume that your gridded data are in a lat-lon grid, but my data were in the Northern and Southern EASE-Grid. Obviously, your situation will be similar for your gridded data sets. I followed recommendations from the NCL tech support team to create the vectors for rows and columns, and then to use those as the 2 dimensions for the latitutde and longitude arrays. I recommend that you use this for the model for your own gridded data contents, because it has been tested with NCL as a "reference" standard tool, and NCL can display the data properly. Due the overhead of imbedding the lat/lon coordinates for each grid cell in the file itself, I chose to create a 3rd "unlimited" dimension for time. Since I was including 8-day data, I considered a year of data a reasonable size to include in a single file. Finally, I deliberately broke the rule to not repeat the same information in 2 places in a file, and included the date stamp for each grid in the file as both a Gregorian (yyyymmdd) date and as a Julian (continuous, real-valued) date (days since -4713). This allows for sorting and plotting data in chronological order, without having to do date format conversions. NL.2007.nsidc0321v01.nc : example file, with "blended" snow data for 2007 (use "ncdump" utility to browse metadata) blended_product_to_netcdf.ncl : NCL script used to create one netCDF file with 2 layers of data for a given date (nccat utility is used to concatenate files for a given year into a single file, reducing geolocation overhead. ************************************************************************ 2) Land/Ocean/Ice-masks for EASE2_N25km and EASE2_N100km: EASE2_N25km_loci_land50_coast0km.720x720.bin EASE2_N25km_loci_land50_coast0km.720x720.png EASE2_N100km_loci_land50_coast0km.180x180.bin EASE2_N100km_loci_land50_coast0km.180x180.png .png files are image renderings of the .bin files. .bin files are flat, binary, with dimensions as listed in the filenames, with 8-bit (1-byte) values representing land, ocean, ice or "corners. Array storage order is row-major, with the first element in the array corresponding to the upper left location in the grid. Mask values were derived from BU-MODIS 1 km IGBP landcover classifications. The BU-MODIS classifications were regridded to the target measures grid, and then used to create the land mask as follows: 0 = land (in >= 50% of component BU-MODIS pixels) 101 = permanent ice ( in >= 50% of component BU-MODIS pixels) 255 = ocean 254 = "corner" pixels (latitudes < 0.0) The coastline width can be set to something larger than 0.0. I didn't get the idea that you wanted or needed this. If you are interested in the actual IGBP layers (there are 17), let me know. I also didn't get the impression that you were interested in that. The regridding process from BU-MODIS land cover data to the EASE2 grids has been developed based on our experience with the BU-MODIS data. There is more detail about it in section "BU-MODIS Land Cover/Processing Notes" at http://nsidc.org/data/ease/ancillary.html If you use these masks in your work, please use this acknowledgement: EASE-Grid-2.0 Land-Ocean-Ice (LOI) Mask, derived from Boston University Version of Global 1 km Land Cover from MODIS 2001, Version 4, according to method defined by K. Knowles, courtesy of M. J. Brodzik. Boulder, Colorado USA: National Snow and Ice Data Center. Digital Media. ************************************************************************ 3) lat/lon grid arrays for EASE2_N25km and EASE2_N100km: lat/lon arrays for the 25 and 100 km N EASE2 grids are: EASE2_N100km.lats.180x180x1.double EASE2_N100km.lons.180x180x1.double EASE2_N25km.lats.720x720x1.double EASE2_N25km.lons.720x720x1.double Files are flat, binary, with dimensions as listed in the filenames, with double-precision (8-byte) values representing decimal degrees. Array storage order is row-major, with the first element in the array corresponding to the upper left location in the grid. Values represent the location of the center of each grid cell. Cell locations south of the equator are considered "off-grid" and are set to -999.00. Double-precision in a lat/lon file like this allows for 1-meter precision. You may not care about that. If you prefer the single-precision version, let me know. Obviously, lat/lon grids don't need to be cited. ************************************************************************ 4) Link to QC summary white paper describing regridding issues encountered in 1994, during development of the Combined Snow and Ice data set at NSIDC. Describes method for resolving artifacts related to resolution and/or different source data land/ocean masks: http://nsidc.org/data/docs/daac/nsidc0046_nh_ease_snow_seaice/QC_summary.html ************************************************************************ 5) mapx libary for OSX and idl_grids library to tie IDL to full mapx functionality. Lastly, Tom Mote was interested in a version of the mapx (C) library that will compile on OSX, and the IDL library that wraps the mapx routines. I'll send this to him directly. I don't want to hold up the rest of this for the IDL/mapx stuff. ************************************************************************ Mary Jo Brodzik 303-492-8263 brodzik@nsidc.org Boulder CO, 5/19/2011