README -- Describes contents of HEMCO/MEGAN/v2018-05
11 Mar 2019
GEOS-Chem Support Team
geos-chem-support@g.harvard.edu


Overview:
===============================================================================

This directory contains the input files for the HEMCO MEGAN2.1 extension and
corrects a bug found in the analogous files stored in v2017-07. This
update applies emission algorithm updates according to Guenther et al. (2012),
enables computation of emissions for more compounds, uses CLM4 plant functional
type distributions, facilitates computing emissions with different/dynamic land
cover schemes, and streamlines the code.

For more information, please see this wiki page:

http://wiki.seas.harvard.edu/geos-chem/index.php/MEGAN_v2.1_plus_Guenther_2012_biogenic_emissions


Email from Jenny Fisher accompanying submission:
===============================================================================

From: Jenny Fisher [mailto:jennyf@uow.edu.au] 
Sent: Thursday, May 31, 2018 12:30 AM
To: GEOS-Chem Support
Cc: Dylan Millet
Subject: Bug fix - MEGAN input files

Dear GCST,

I’ve discovered a bug in some of the high-resolution files used for MEGAN
(previously provided in the MEGAN/v2017-07/). For one species (alpha pinene)
there was a strange offset of the grid that affected the southernmid-latitudes.
With Dylan’s help, we traced this to the original very high resolution MEGAN
input files provided by Alex Guenther’s group. These were updated in Nov 2016,
removing the offset.

I’ve recreated the HEMCO-ready version of these files, and they are available
for download here:
https://www.dropbox.com/s/5ln6ew92ftjd1hm/v2018-05.zip?dl=0

This is definitely a bug fix, so should get implemented during the v11-02
provisional release period (really just a file update so it’s easy).

Note that the update will ONLY affect anyone looking at monoterpenes
(specifically MTPA) in the southern mid-latitudes  see attached difference plot.

Let me know if you have any questions!

Cheers,
Jenny


Files:
===============================================================================

NOTE: GCST rechunked and compressed the netcdf files after receiving them

MEGAN2.1_EF.geos.025x03125.nc

 -- Annual emission factor (AEF) data from the MEGAN 2.1 inventory for the 
    various biogenic hydrocarbon species:

    ALPHA_PINENE, BETA_PINENE, CARENE,  ISOPRENE, LIMONENE,      
    MBO,          MYRCENE      OCIMENE, SABINENE, ACETONE

    These files were converted to netCDF from the original bpch files
    created by Dylan Millet.
 
    Resolution  : GEOS-Chem 0.25 x 0.3125 grid (1152 x 721 boxes)
    Units       : kg carbon m-2 s-1
    Timestamps  : 1985/01
    Compression : Level 1 (e.g. nccopy -d1)
    Chunking    : nccopy -c lon/1152,lat/721,time/1


MEGAN2.1_EF.geos.1x1.ugm-2hr-1.nc

 -- Contains the same data as in MEGAN2.1_EF.geos.1x1.nc, but the units
    are ug carbon m-2 hour.  This is kept for compatibility for older code
    but is not used in the standard HEMCO distribution.

    Resolution  : GEOS-Chem 0.25 x 0.3125 grid (1152 x 721 boxes)
    Units       : ug carbon m-2 hour-1
    Timestamps  : 1985/01
    Compression : Level 1 (e.g. nccopy -d1)
    Chunking    : nccopy -c lon/1152,lat/721,time/1


References:
===============================================================================

Please see this wiki page for references pertaining to the MEGAN emissions:

http://wiki.geos-chem.org/MEGAN_v2.1_plus_Guenther_2012_biogenic_emissions#References