The online lidar system is located in Oberpfaffenhofen, near Munich, Bavaria. Another one in Europe is located in Reading, England
The system operates 24 hours a day, producing vertical aerosol profiles every 30 seconds.A slant scanning procedure is in principle possible, but prevented here by the plantation. The laser emits radiation with a wavelength about 900 nanometer at a peak pulse power of 30 W, but with an expanded beam of 10 cm diameter. The repetition rate of 6 kHz still fulfills class 1 eye-safety criteria, but it is nevertheless neccessary to accumulate some ten thousand shots.
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The graph at the right shows the last intensity profile of the backscattered radiation (horizontal axis, arbitrary units) vs. altitude (vertical axis, meters). In the case that a cloud exists in the measurement volume (100 - 3500 meters), a characteristic peak will appear and the numerical displays (cloud information: 1. layer, 2. layer) above the graph will indicate the cloud ceiling altitude.
The intensity plot on the left shows the time series of 24 hours total, the red vertical line indicates the current position, on the right side of the mark data from the day before are plotted whereas the left side represents the actual day.
Clear air is indicated by light colour, increasing blue from morning till evening is caused by the increasing background radiation of the daylight, even when using a very tight optical filter before the receiver photo diode. So sunrise and sundown can be easely detected by the different standard deviation of the noise contribution.
The presence of a cloud is indicated by dark coloured patches, rain will be visible as well as snow when falling out of the clouds. A strong peak close to the origin (the first 500 metres) represents high turbidity which means fog, heavy rainfall or snowfall. The real values of the number of scatterers, the extinction coefficient of the atmosphere, can be determined from the above data by inverting the lidar signal.
From the simple plot of the raw data signal one can already identify:
DLR, Institut für Physik der Atmosphäre
P.O.B. 1116 - 82230 Weßling
Contact: Jürgen Streicher
Tel.: +49 8153 28-1609
Fax: +49 8153 28-1271