README -- Describes contents of HEMCO/TIMEZONES/v2015-02 directory 04 Jan 2017 GEOS-Chem Support Team geos-chem-support@g.harvard.edu Overview: =============================================================================== Christoph Keller wrote: Local times can now be calculated based on a time zone map provided through the HEMCO configuration file. This file is expected to be named ‘TIMEZONES’ and must contain the UTC offsets (in hours) for each grid box. These offsets will then be used when calculating the local times. If no such file is provided - or an invalid value is encountered in a given grid box (e.g. -999) - local times are calculated with the previous method, e.g. as a function of longitude (assuming each time zone spans 15 degrees in longitudinal direction). The timezone functionality can be specified by adding this line to your HEMCO Configuration file: TIMEZONES $ROOT/TIMEZONES/v2015-02/timezones_edit_1x1.nc UTC_OFFSET 2000/1/1/0 C xy count * - 1 1 We plan to include this new timezone feature of HEMCO into GEOS-Chem v10-01h and higher versions. Files: =============================================================================== timezones_1x1.edit.nc %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%% THIS IS THE DEFAULT SETTING FOR GEOS-Chem v11-01 (Jan 2017) %%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Contains the offset from UTC for each of the world's 24 time zones. This is used by HEMCO for emissions that depend on local time. The original timezones mask file does not work properly in grid cells with large ocean overlap. The problem is that the ocean values are _FillValues that become zero within HEMCO. This file contains a fix to use a value of -5000 in all ocean cells, which forces HEMCO to determine the timezone based on longitude in those cells. Resolution : GENERIC 1 x 1 grid (360 x 180 boxes) Units : hours Timestamp : 2000/01 Compression : Level 1 (e.g. nccopy -d1) timezones_voronoi_1x1.nc %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%% THIS IS CURRENTLY OPTIONAL FOR GEOS-Chem v11-01 (Jan 2017) %%%% %%%% PENDING VALIDATION, THIS WILL BE MADE THE DEFAULT SETTING %%%% %%%% PROVBABLY IN GEOS-Chem v11-02. USE AT YOUR OWN RISK. %%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Contains the offset from UTC for each of the world's 24 time zones. Ocean grid boxes are given the time zone of the nearest-neighbor land cell as determined by the great circle distance (Voronoi method). Seb Eastham (seastham@fas.harvard.edu) wrote: I'd like to suggest that this replace the default HEMCO "timezones" file (aka "timezones_edit_1x1.nc"). This replacement ensures that coastal areas have the same timezones as the landmass to which they are attached. Without the update, some coastal areas will use the wrong timezone, resulting in incorrect diurnal scalings. This new approach sets the timezone in every ocean cell to match that of the closest valid cell (by great circle distance). Resolution : GENERIC 1 x 1 grid (360 x 180 boxes) Units : hours Timestamp : 2000/01 Compression : Level 1 (e.g. nccopy -d1) timezones_1x1.nc %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%% THIS WAS THE DEFAULT SETTING PRIOR TO GEOS-CHEM v11-01, %%%% %%%% BUT IS NOW OBSOLETE AND SHOULD NO LONGER BE USED. %%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Contains the offset from UTC for each of the world's 24 time zones. This is used by HEMCO for emissions that depend on local time. Resolution : GENERIC 1 x 1 grid (360 x 180 boxes) Units : hours Timestamp : 2000/01 Compression : Level 1 (e.g. nccopy -d1) How the files were created: =============================================================================== The scripts and raw data used to create the timezones_1x1.nc file are contained in the TARBALL file HEMCO/ROOT/raw_data/TIMEZONES.tar.gz.