 |
Atmospheric water vapor measuring system
Water vapor belongs to the most important trace gases of the atmosphere. In form of clouds it is by far the most effective greenhouse gas, together with ozone it is the main source of tropospheric OH radicals, and it plays an important role in transporting latent heat from low to high altitudes. For studying atmospheric chemistry and the dynamics in the upper troposphere and lower stratosphere by using aircraft, it is a basic necessity to have a hygrometer on board. The typical water mixing ratios in this area are 4 to 1000 ppmv, while the pressure changes from ~150 up to ~400 mbar.
In spite of its paramount importance, there is still a need for new fast and robust detectors for high sensitive, selective water vapor detection with wide dynamic range and capability of long-term unattended operation under varying environmental conditions.
Our photoacoustic research group has developed a DFB diode laser based photoacoustic water vapor detector for airborne operation. It was proven that the detector characteristics fulfill all the above mentioned requirements of atmospheric applications.
We have demonstrated the high sensitivity of the detector and its wide dynamic range (from 0.2 ppm up to a few thousand ppm). Furthermore, the detector measures the water vapor in interference-free mode, so the components existing in the atmosphere do not affects the detector measurement accuracy. Experiments were performed, which proved that the varying environmental conditions (e.g. temperature and gas pressure) do not disturb significantly the sensitivity of the detector.
The water vapor detector is utilized on-board a commercial aircraft (Airbus A340-600 of Lufthansa) within the project CARIBIC since May 2005.
|
|
 |
Our multi-wavelength photo- acoustic aerosol system was successfully tested in a measurement campaign at the Research Center Karlsruhe (18-28 April 2006).
|
|
|
