Units for emissions passed into Hector

The “Unit Symbol” is the symbol used in the code for the unit. They are all part of the Hector:: namespace, so in actual use you would write Hector::U_TG, etc. In most cases the “per year” is left implicit, so emissions in Tg/yr are written as U_TG. The notable exception is CO₂, where the code tracks both carbon fluxes and carbon pools, and must therefore make a distinction.

Where a mass unit is given without qualification, such as Tg/yr, the mass is the total mass of the emitted compound. This is to be distinguished from, say Tg N/yr or Pg C/yr, where the mass refers only to the nitrogen or carbon in the emissions. Many compounds have units that explicitly refer to the total mass, such as Tg CO/yr for carbon monoxide. Such units are technically the same as a plain Tg/yr (and have been written that way in the table), but the code treats them separately and will not convert them automatically, so be sure to use the unit symbol given for passing in your emissions. Passing an incorrect unit, even if technically equivalent, will cause Hector to throw an exception.

Emission	Units	Unit Symbol	Notes
CO2 emissions	Pg C/yr	U_PGC_YR	same units for land use change and anthropogenic emissions
BC	Tg/yr	U_TG
OC	Tg/yr	U_TG
NOx	Tg N/yr	U_TG_N
CO	Tg/yr	U_TG_CO
NMVOC	Tg/yr	U_TG_NMVOC
CH4	Tg/yr	U_TG_CH4
N2O	Tg/yr	U_TG_N2O	Note difference with NOx, which uses Tg N
SO2	Gg S/yr	U_GG_S
halocarbons	Gg/yr	U_GG	All halocarbons use the same unit.

Units for Hector outputs

Hector outputs are returned as unitval structures, so if there is any doubt, you can always dump the return value to an output stream to see what the unit is (or test the units field against likely candidates). What follows is a non-exhaustive list of some of the commonly-used outputs.

Value	Units	Unit Symbol	Notes
Forcings	W/m2	U_W_M2	All forcings given in W/m2 relative to baseline
Temperature	degrees C	U_DEGC	Temperature anomaly
Atmospheric CO2 concentration	PPMv CO2	U_PPMV_CO2

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See also unitval notes