Background current correction (IBG) is caused by oxidants other than ozone (mainly O2). Because the concentration of ozone without any additional oxidants needs to be measured, the background current has to be deducted from the measurement current.
The amount of oxidants (mainly oxygen) decreases during sounding when ambient pressure decreases. The background current IBG is counted from the following equation recommended for the SPC ECC-6A sensor.
- I0
- Background current I0 is measured using ozone destruction filter through which air is pumped during the sounding preparation activities, just before release.
- P
- Ambient pressure in hPa
- P0
- Ambient pressure when Io is measured in hPa ~ ground pressure
- A0
- 0.00122504
- A1
- 0.0001241115
- A2
- -2.687066 × 10-8
The Model Z sensor recommended correction is constant:
IBG = Io
when Io is measured just before release during sounding setup configuration.
By setting the background current Io = 0, the background current correction is disabled.
The ASOPOS panel recommends the use of a constant, pressure independent IB2 in the basic equation to determine the ozone partial pressure throughout the entire vertical profile. Pressure-dependent background can be done by:
I0 = (P/P0) x IB2
As a Vaisala equation, this is:
IBG = (P/P0) x IO