Rotational Raman Lidar, UHOH RRL

The rotational Raman lidar of University of Hohenheim (UHOH RRL) provides high resolution data of temperature, particle backscatter coefficient, and particle extinction coefficient at 355 nm both in day and at night (Radlach et al., 2008, Radlach 2009). The UHOH RRL filters were optimized for measurements from close to the ground to the middle troposphere. This is the reason why this system is the only RRL worldwide which provides temperature profiles with a temporal resolution of 10 – 60 s with a range resolution of ~100 m and an accuracy of better 1 K also in daytime.
The UHOH RRL emits UV laser pulses at 354.7 nm (50 Hz, ~240 mJ/pulse), collects the backscatter signal with a telescope with a 40-cm primary mirror and extracts three signals out of the backscatter spectrum: the elastic-backscatter signal of molecules and aerosols at 354.7 nm and two rotational Raman backscatter signals near 353.1 nm and 354.1 nm which show opposite temperature dependency. The ratio of the latter two provides after calibration directly and without any a-priory assumption on the state of the atmosphere a profile of the atmospheric temperature (Behrendt 2005). Like for any other lidar, the temporal and range resolution of the derived lidar data products can be traded off against each other. Therefore, the UHOH RRL data are stored with a raw data resolution of 10 s and 3.75 m up to a range of 20 km and with 37.5 m resolution up to 75 km. These data are available for detailed post-processing. The UHOH RRL contains a scanner so that the profiles can be measured in any direction of interest which is highly beneficial for boundary layer studies.

Scanning measurements of potential temperature and particle backscatter coefficient at 355 nm with the UHOH RRL during COPS. 13 scans at 21 elevations with 13 s sampling for each profile were averaged. In the potential temperature field and the aerosol field clear horizontal differences can be seen towards the Rhine Valley in the west and the Murg Valley in the east.