Emission inventories sometimes include dynamic source types and nonlinear scale factors that have functional dependencies on local environmental variables such as wind speed or temperature, which are best calculated online during execution of the model. HEMCO includes a suite of additional modules (extensions) that perform online emission calculations for a variety of sources (see list below). Extensions are enabled in section Extension Switches of the HEMCO configuration file.
List of extensions¶
The full list of available extensions is given below. Extensions can be selected individually in the Extension Switches section of the The HEMCO configuration file, as can the species to be considered.
Species: DSTAL1, DSTAL2, DSTAL3, DSTAL4
Reference: Fairlie et al (check)
Emissions of mineral dust from the DEAD dust mobilization model.
Species: DST1, DST2, DST3, DST4
Reference: Zender et al. 
Emissions of mineral dust from the P. Ginoux dust mobilization model.
Species: DST1, DST2, DST3, DST4
Reference: Ginoux et al. 
Biomass burning emissions from the FINN model.
Species: NO, CO, ALK4, ACET, MEK, ALD2, PRPE, C2H2, C2H4, C3H8, CH2O, C2H6, SO2, NH3, BCPI, BCPO, OCPI, OCPO, GLYC, HAC, SOAP
Reference: Wiedinmyer et al. 
Emissions of radionuclide species as used in the GEOS-Chem model.
Species: Rn222, Be7, Be7Strat, Be10, Be10Strat
Biomass burning emissions from the GFED model.
Version: GFED3 and GFED4 are available.
Species: NO, CO, ALK4, ACET, MEK, ALD2, PRPE, C2H2, C2H4, C3H8, CH2O C2H6, SO2, NH3, BCPO, BCPI, OCPO, OCPI, POG1, POG2, MTPA, BENZ, TOLU, XYLE NAP, EOH, MOH, SOAP,
Reference: van der Werf et al. 
Species: HOI, I2
Biogenic VOC emissions.
Species: ISOP, ACET, PRPE, C2H4, ALD2, CO, OCPI, MONX, MTPA, MTPO, LIMO, SESQ
Reference: Guenther et al. 
Sea salt aerosol emission.
Emissions of volcanic SO2 from AEROCOM.
Size-resolved sea salt emissions for TOMAS aerosol microphysics simulations.
Species: SS1, SS2, SS3, SS4, SS5, SS6, SS7, SS8, SS9, SS10, SS11, SS12, SS13, SS14, SS15, SS16, SS17, SS18, SS19, SS20, SS21, SS22, SS23, SS24, SS25, SS26, SS27, SS28, SS29, SS30, SS31, SS32, SS33, SS34, SS35, SS36, SS37, SS38, SS39, SS40
Reference: Jaeglé et al. 
Size-resolved dust emissions for TOMAS aerosol microphysics simulations.
Species: DUST1, DUST2, DUST3, DUST4, DUST5, DUST6, DUST7, DUST8, DUST9, DUST10, DUST11, DUST12, DUST13, DUST14, DUST15, DUST16, DUST17, DUST18, DUST19, DUST20, DUST21, DUST22, DUST23, DUST24, DUST25, DUST26, DUST27, DUST28, DUST29, DUST30, DUST31, DUST32, DUST33, DUST34, DUST35, DUST36, DUST37, DUST38, DUST39, DUST40
Reference: Zender et al. 
HEMCO can host all environmentally independent data sets (e.g. source functions) used by the extensions. The environmental variables are either provided by the atmospheric model or directly read from file through the HEMCO configuration file. Entries in the HEMCO configuration file file are given priority over fields passed down from the atmospheric model, i.e. if the HEMCO configuration file contains an entry for a given environmental variable, this field will be used instead of the field provided by the atmospheric model. The field name provided in the HEMCO configuration file must exactly match the name of the HEMCO environmental parameter.
To use the NCEP reanalysis monthly surface wind fields (http:, , www.esrl.noaa.gov, psd, data, gridded, data.ncep.reanalysis.derived.surface.html) in all HEMCO extensions, add the following two lines to the Base Emissions section of the HEMCO configuration file:
* U10M /path/to/uwnd.mon.mean.nc uwnd 1948-2014/1-12/1/0 C xy m/s * - 1 1 * V10M /path/to/vwnd.mon.mean.nc vwnd 1948-2014/1-12/1/0 C xy m/s * - 1 1
This will use these wind fields for all emission calculations, even if the atmospheric model uses a different set of wind fields.
It is legal to assign scale factors (and masks) to the environmental variables read through the HEMCO configuration file. This is particularly attractive for sensitivity studies. For example, a scale factor of 1.1 can be assigned to the NCEP surface wind fields to study the sensitivity of emissions on a 10% increase in wind speed:
In the Base Emissions section:
* U10M /path/to/uwnd.mon.mean.nc uwnd 1948-2014/1-12/1/0 C xy m/s * 123 1 1 * V10M /path/to/vwnd.mon.mean.nc vwnd 1948-2014/1-12/1/0 C xy m/s * 123 1 1
In the Scale Factors section:
123 SURFWIND_SCALE 1.1 - - - xy 1 1
As for any other entry in the HEMCO configuration file, spatially uniform values can be set directly in the HEMCO configuration file. For example, a spatially uniform, but monthly varying surface albedo can be specified by adding the following entry to the Base Emissions section of the HEMCO configuration file:
* ALBD 0.7/0.65/0.6/0.5/0.5/0.4/0.45/0.5/0.55/0.6/0.6/0.7 - 2000/1-12/1/0 C xy 1 * - 1 1
Environmental fields used by HEMCO¶
The following fields can be passed from the atmospheric model to HEMCO for use by the various extensions:
Fraction of grid box within the planetary boundary layer (PBL).
Snow height (mm of H2O equivalent).
E/W wind speed @ 10 meters above surface.
N/S wind speed @ 10 meters above surface.
Water-land-ice flags (
Used by: Almost every extension
Some extensions rely on restart variables, i.e. variables that are
highly dependent on historical information such as previous-day leaf
area index or soil NOx pulsing factor. During a simulation run, the
extensions continuously archive all necessary information and update
estart variables accordingly. The updated variables become
automatically written into the HEMCO restart file
HEMCO_restart.YYYYMMDDhhmmss.nc) at the end of a
simulation. The fields from this file can then be read through the
HEMCO configuration file to resume the simulation at this date (“warm”
restart). For example, the soil NOx restart variables can be made
available to the soil NOx extension by adding the following lines to
the Base Emissions section of the HEMCO
104 PFACTOR ./HEMCO_restart.$YYYY$MM$DD$HH00.nc PFACTOR $YYYY/$MM/$DD/$HH E xy unitless NO - 1 1 104 DRYPERIOD ./HEMCO_restart.$YYYY$MM$DD$HH00.nc DRYPERIOD $YYYY/$MM/$DD/$HH E xy unitless NO - 1 1 104 GWET_PREV ./HEMCO_restart.$YYYY$MM$DD$HH00.nc GWET_PREV $YYYY/$MM/$DD/$HH E xy unitless NO - 1 1 104 DEP_RESERVOIR ./HEMCO_restart.$YYYY$MM$DD$HH00.nc DEP_RESERVOIR $YYYY/$MM/$DD/$HH E xy unitless NO - 1 1
Many restart variables are very time and date-dependent. It is therefore recommended to set the time slice selection flag to E to ensure that only data is read that exactly matches the simulation start date (also see Base emissions. HEMCO will perform a “cold start” if no restart field can be found for a given simulation start date, e.g. default values will be used for those restart variables.
Built-in tools for scaling/masking¶
HEMCO has built-in tools to facilitate the application of both uniform and spatiotemporal scale factors to emissions calculated by the extensions. At this point, not all extensions take advantage of these tools yet. A list of extensions that support the built-in scaling tools are given below.
For extensions that support the built-in scaling tools, you can specify the uniform and/or spatiotemporal scale factors to be applied to the extension species of interest in section Extension switches the HEMCO configuration file.
For example, to uniformly scale GFED CO by a factor of 1.05 and GFED NO emissions by a factor of 1.2, add the following two lines to the HEMCO configuration file (highlighted in GREEN):
111 GFED : on CO/NO/ACET/ALK4 --> GFED3 : false --> GFED4 : true --> GFED_daily : false --> GFED_3hourly : false --> Scaling_CO : 1.05 --> Scaling_NO : 1.20
Similarly, a spatiotemporal field to be applied to the species of
interest can be defined via setting
111 GFED : on CO/NO/ACET/ALK4 --> GFED3 : false --> GFED4 : true --> GFED_daily : false --> GFED_3hourly : false --> Scaling_CO : 1.05 --> Scaling_NO : 1.20 --> ScaleField_NO : GFED_SCALEFIELD_NO
The corresponding scale field needs be defined in section Base emissions . A simple example would be a monthly varying scale factor for GFED NO emissions:
111 GFED_SCALEFIELD_NO 0.9/1.1/1.3/1.4/1.6/1.7/1.7/1.8/1.5/1.3/0.9/0.8 - 2000/1-12/1/0 C xy unitless * - 1 1
It is legal to apply scale factors and/or masks to the extension scale fields (in the same way as the ‘regular’ base emission fields). A more sophisticated example on how to scale soil NOx emissions is given in HEMCO examples.
Extensions supporting built-in scaling/masking¶
Adding new HEMCO extensions¶
All HEMCO extensions are called through the extension interface
every new extension, a corresponding subroutine call needs to be added
to those three routines. You will quickly see that these calls only
take a few arguments, most importantly the HEMCO state object
HcoState and the extensions state object
ExtState is defined in
HEMCO/src/Extensions/hcox_state_mod.F90. It contains logical
switches for each extension as well as pointers to any external data
(such as met fields). For a new extension, you’ll have to add a new
logical switch to the Ext_State object. If you need external data that
is not yet included in ExtState, you will also have to add those
(including the pointer associations in subroutine
The initialization call (
HCOX_XXX_INIT) should be used to
initialize all extension variables and to read all settings from the
HEMCO configuration file. There are a number of helper routines in
HEMCO/src/Extensions/hco_extlist_mod.F90 to do this:
GetExtNr( ExtName )returns the extension number for the given extension name. Will return –1 if extension is turned off!
GetExtOpt( ExtNr, Attribute, Value, RC )can be used to read any additional extension options (logical switches, path and names of csv-tables, etc.). Note that value can be of various types (
GetExtHcoID( HcoState, ExtNr, HcoIDs, SpcNames, nSpc, RC )matches the extension species names (as defined in the configuration file) to the species defined in HEMCO state (i.e. to all available HEMCO species). A value of –1 is returned if the given species is not defined in HEMCO.
ExtState variables used by this extension should be
updated. This includes the logical switch and all external data needed
by the extension. For example, if the extension needs temperature
data, this pointer should be activated by setting
ExtState%TK%DoUse = .TRUE.
The run call (
HCOX_XXX_RUN) calculates the 2D fluxes and
passes them to HcoState via subroutine
Flux, HcoID, RC). External data is assessed through
ExtState%TX%Arr%Val(I,J,L)), and any data automatically
read from netCDF files (through the HEMCO interface) can be obtained
EmisList_GetDataArr( am_I_Root, FieldName, Pointer,
RC ) The body of the run routine is typically just the code of the
It’s probably easiest to start from an existing extension (or the
Custom extension template) and to add any modifications as is