Grid-independent emissions
These emissions were be implemented in GEOS-Chem 12.4.0.
Overview
The grid-independent emissions were identified as a priority during the development of GCHP, which uses cubed-sphere grids instead of the traditional lat-lon grids used by GEOS-Chem "Classic". As such, emissions that utilized resolution-dependent scale factors (e.g. dust and lightning) posed a challenge. The solution was to use grid-independent emissions saved out at high-resolution that would be regridded to the simulation grid at run time via HEMCO.
The grid-independent (aka offline) emissions were implemented in GEOS-Chem 12.5.0. They are available at 0.25° x 0.3125° and 0.5° x 0.625°, which correspond to the native horizontal resolution of the GEOS-FP and MERRA-2 meteorology fields used to drive GEOS-Chem. The offline emissions were generated by running the HEMCO standalone with the analogous online emissions (or HEMCO extension) turned on.
- Offline dust emissions were generated with the DustDead extension
- Offline biogenic VOC emissions were generated with the MEGAN extension
- Offline sea salt emissions were generated with SeaSalt extension
- Offline soil NOx emissions were generated with the SoilNOx extension
By default, these offline emissions are turned on. To use the online emissions instead, set the offline emissions (OFFLINE_DUST, OFFLINE_BIOGENICVOC, OFFLINE_SEASALT, and/or OFFLINE_SOILNOX) to false at the top of HEMCO_Config.rc and set the corresponding HEMCO extension (DustDead, MEGAN, SeaSalt, and/or SoilNOx) to on.
Download
The grid-independent emissions are stored on at the WashU data portal and may be accessed at the following address:
http://geoschemdata.wustl.edu
A copy of the grid-independent emissions may be found on the Harvard and Dalhousie data archives, but they are not guaranteed to be up-to-date or contain all years available.
Dust emissions
Developers: David Ridley (CARB, formerly MIT), Jun Meng (Dalhousie)
README: http://geoschemdata.wustl.edu/ExtData/HEMCO/OFFLINE_DUST/v2021-08/README
Please see this post on the Mineral Dust Aerosols wiki page for a details about the offline dust emissions.
Lightning NOx emissions
Developer: Lee Murray (Rochester)
README: http://geoschemdata.wustl.edu/ExtData/HEMCO/OFFLINE_LIGHTNING/v2020-03/GEOSFP/README
Biogenic VOC emissions
Developer: Jintai Lin (PKU) and Hongjian Weng (PKU)
README: http://geoschemdata.wustl.edu/ExtData/HEMCO/OFFLINE_BIOVOC/v2021-12/README.txt
Grid-independent offline biogenic VOC emissions are now available for GEOS-Chem at native MERRA-2 (0.5° x 0.625°) and GEOS-FP (0.25° x 0.3125°) meteorology field resolution. The emissions used in GEOS-Chem 12.5.0 and later were generated with GEOS-Chem 12.3.0 using the Yuan-processed MODIS XLAI.
Sea salt emissions
Developer: Jintai Lin (PKU) and Hongjian Weng (PKU)
README: http://geoschemdata.wustl.edu/ExtData/HEMCO/OFFLINE_SEASALT/v2019-01/README
Soil NOx emissions
Developer: Jintai Lin (PKU) and Hongjian Weng (PKU)
README: http://geoschemdata.wustl.edu/ExtData/HEMCO/OFFLINE_SOILNOX/v2021-12/README.txt