Updates and corrections to the GMI chemical mechanism and its input files have been used to create a new Hindcast simulation with MERRA2 meteorology. The changes compared to the previous GMI simulation are generally small and you probably won’t see any large impacts on chemical constituents. The greatest impacts are on temporal and spatial evolution of polar ozone depletion and on NOy partitioning globally due a change in stratospheric sulfate surface area. Mechanism and input changes are listed below.
The new GMI support files have ‘MR2V3’ in the file name, indicating that the output was created from a simulation using MERRA2 and that this is the 3rd version submitted to the NDACC data repository.
There is no significant change to file format or composition. Files for all lidar, sonde, and Dobson stations contain hourly vertical profiles of O3, NO2, H2O, temperature, pressure, and potential vorticity at 0.75 km resolution from the surface to 60 or 0-75 km, depending on the variable. Model files for FTIR stations have temperature, pressure, and tropopause pressures reported at both the 1-2 pm local time and 12z. The simulated species reported at 1-2 pm are O3, CO, CH2O, NO, and NO2; all other daily species are still reported at 12z. BrO profiles and columns are reported as monthly averages.
All files can be downloaded at https://www-air.larc.nasa.gov/missions/ndacc/data.html?GMI_MODEL=gmi-li….
Changes to the Chemical Mechanism and its inputs are:
- CMIP6 rather than IGAC is now the source of the stratospheric sulfate surface area density (SAD) climatology. The climatology runs from 1980-2015. The 36-yr mean is used for 2016-2020.
- Changes to the PSC parameterization settings were made that affect particle distribution
- Updated to the most recent sunspots for galactic cosmic ray inputs
- Emission inventories updated
- Convective mass flux bug was fixed that affects calculation of lightning flashrates.
- Updated boundary conditions to reflect new ground-level observations of CFCs and CH4.
- Most recent solar cycle for fastJX is now included.
- Fixed Cly family transport packing/unpacking that caused a small sink for Cl in the stratosphere; affects polar chemistry
- Corrected Henry’s Law (h*) wet & dry scavenging coefficients (they were swapped in the previous simulation)
As always, please contact Susan Strahan (susan.e.strahan@nasa.gov) for additional model support or questions.