# ``co2_mole_fraction``
## Properties
:dimensions: N_PROF, N_LEVELS
:dtype: float64
## Default Attributes
| Attribute | Value |
|-----|-----|
|``whp_name`` | ``XCO2`` |
|``whp_unit`` | ``PPM`` |
|``units`` | ``1e-6`` |
|``C_format`` | ``%9.1f`` |
|``C_format_source`` | ``database`` |
## Description
The mole fraction of CO2 in air, wet or dry is unknown.
:::{warning}
This parameter was added because we found several cruises with "PCO2" reported as ppm. The only notes that could we could find where questioning if the values were "wet" or "dry", which is wondering if pH2O was taken into account. XCO2 as a name was taken from the definition of CO2 expressed as PPM in CO2SYS V25.

Use caution if you are trying to compare this parameter to other (p/f/x)CO2 data
:::