README -- describes contents of HEMCO/UVALBEDO/v2015-03 directory 06 Jun 2019 GEOS-Chem Support Team geos-chem-support@g.harvard.edu Overview: =============================================================================== This directory contains UV albedo data, which is used as an input to the FAST-JX photolysis mechanism. It contains the same data as stored in v2015-03 but with minor modification to the time dimension unit string for compatibility with GEOS-Chem 12.5.0, specifically MAPL in GCHP. Reference: ---------- Herman, J.R. and E.A. Celarier, "Earth surface reflectivity climatology at 340-380 nm from TOMS data", J. Geophys. Res., 102(D23), 28,003-28,011. (1997) Files: =============================================================================== uvalbedo.geos.2x25.nc -- Monthly mean UV albedoes (340 nm - 380 nm, from TOMS) Source : Hermann & Celarier (1997) Resolution: : GEOS-Chem 2 x 2.5 grid (144 x 91 boxes) Units : % Timestamps : Monthly, 1985/01 thru 1985/12 Compression : Level 1 (e.g. nccopy -d1) NOTE: The HEMCO philosophy is to use the data at the highest resolution possible. In GEOS-Chem version v10-01 and later versions, we recommend reading the 2 x 2.5 UV albedo data via HEMCO. This will be regridded to the resolution of your CTM simulation. uvalbedo.geos.4x5.nc -- Monthly mean UV albedoes (340 nm - 380 nm, from TOMS) Source : Hermann & Celarier (1997) Resolution: : GEOS-Chem 4 x 5 grid (144 x 91 boxes) Units : % Timestamps : Monthly, 1985/01 thru 1985/12 Compression : Level 1 (e.g. nccopy -d1) NOTE: We provide the uvalbedo.geos.4x5.nc file for backwards compatibility. Prior to GEOS-Chem v10-01, GEOS-Chem 4 x 5 simulations read the UV albedo at 4 x 5 resolution. If you would like to compare the output of your 4 x 5 GEOS-Chem simulations with older model versions, then we recommend to read the uvalbedo.geos.4x5.nc file via HEMCO. This will prevent any differences that might be introduced by the regridding of the UV albedo data from the 2 x 2.5 grid to the 4 x 5 grid. How the netCDF files wwere created: =============================================================================== The above files were created as follows: 1) Convert orignal bpch file to netCDF with GAMAP bpch2coards.pro routine IDL> bpch2coards, 'uvalbedo.geos.2x25', 'uvalbedo.geos.2x25.%DATE%.nc' this created the following files: uvalbedo.geos.2x25.19850101.nc uvalbedo.geos.2x25.19850201.nc uvalbedo.geos.2x25.19850301.nc uvalbedo.geos.2x25.19850401.nc uvalbedo.geos.2x25.19850501.nc uvalbedo.geos.2x25.19850601.nc uvalbedo.geos.2x25.19850701.nc uvalbedo.geos.2x25.19850801.nc uvalbedo.geos.2x25.19850901.nc uvalbedo.geos.2x25.19851001.nc uvalbedo.geos.2x25.19851101.nc uvalbedo.geos.2x25.19851201.nc 2) Concatenate the monthly files into a single netCDF file: ncrcat -h -O uvalbedo.geos.2x25.1985*.nc uvalbedo.geos.2x25.nc and then discard the monthly files. 3) Make the data array compatible with GAMAP: ncrename -v UVALBEDO__UVALBD,UVALBD uvalbedo.geos.2x25.nc ncatted -a gamap_category,UVALBD,o,c,"UVALBEDO" uvalbedo.geos.2x25.nc 4) Add several global attributes for better COARDS compliance ncatted -a Title,global,o,c,"UV albedo data from Hermann & Celarier (1997)" uvalbedo.geos.2x25.nc ncatted -a History,global,o,c,"Tue Mar 3 12:18:38 EST 2015" uvalbedo.geos.2x25.nc ncatted -a ProductionDateTime,global,o,c,"Tue Mar 3 12:18:38 EST 2015" uvalbedo.geos.2x25.nc ncatted -a ModificationDateTime,global,o,c,"Tue Mar 3 12:18:38 EST 2015" uvalbedo.geos.2x25.nc ncatted -a Contact,global,o,c,"GEOS-Chem Support Team (geos-chem-support@g.harvard.edu)" uvalbedo.geos.2x25.nc ncatted -a References,global,o,c,"www.geos-chem.org; wiki.geos-chem.org" uvalbedo.geos.2x25.nc 5) Repeat steps 1-4 for to convert binary punch file uvalbedo.geos.4x5 to netCDF file uvalbedo.geos.4x5.nc. UPDATES 6/16/15: =============================================================================== Edited the attributes of uvalbedo.geos.2x25.nc and uvalbedo.geos.4x5.nc as follows: (1) Change units from "%" to "percent". This seems to avoid a formatting error in the HEMCO.log file. For some reason, Unix thinks that the HEMCO.log file is binary when it is not. Issued these commands: ncatted -a units,UVALBD,o,c,"percent" uvalbedo.geos.2x25.nc ncatted -a units,UVALBD,o,c,"percent" uvalbedo.geos.4x5.nc -- Bob Yantosca (16 Jun 2015)