Instrumental effects on the vertical profiles
At RMIB ozone soundings have been performed since 1969. During more than 30 years of observations the procedures of handling the sensors have been subject to changes. Some changes had an influence on the measured ozone concentrations. Efforts have been made to reduce the errors and to construct a homogeneous time series.
One of the most striking influences on the measured ozone concentrations during the 1970s, were the high SO2 concentrations in the atmosphere. When the ambient air is bubbled through a wet chemical cell, which is filled with Potassium Iodide solutions, the ozone molecules react with the solution producing a current in the cell. Also, when SO2 is bubbled, the sensor produces an opposite current. Sometimes the SO2 pollution in the planetary boundary layer (PBL) was so abundant, that we measured negative ozone concentrations. Therefore we had to correct for SO2.
Other important influences on measuring the ozone concentrations are:
- response time
- box temperature
- altitude measurements
- background current
- pump efficiency and total ozone
- different types of sensors
The time series have been homogenised and are very valuable for further research. The full report about the homogenisation procedure is available here (pdf: 418 kb) and is also described in a more recent publication (link to paper).