Browsing by Subject "Raman lidar"

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A scanning eye-safe rotational Raman lidar in the ultraviolet for measurements of tropospheric temperature fields
(2009) Radlach, Marcus; Wulfmeyer, Volker
Within the frame of the virtual Institute COSI-TRACKS the first scanning rotational Raman lidar has been developed and deployed successfully in two large field campaigns. This has allowed new investigations of the convective boundary layer and contributed to studies on the initiation of convection during the PRINCE campaign (PRediction, Identification and trackiNg of Convective cElls) in July 2006 and the COPS experiment (Convective and Orographically-induced Precipitation Study) from June to August 2007. The University of Hohenheim rotational Raman lidar was deployed in both these campaigns on Hornisgrinde (48.61 °N, 8.20 °E, 1161 m above sea level), the highest peak in the Northern Black Forest in southwest Germany. The lidar provides measurements of atmospheric temperature fields in the troposphere with high spatial and temporal resolution at day and night. Daytime scanning temperature measurements within a range of 3 km using a temporal resolution of 169 s and a moving average of 300 m in range show statistical temperature uncertainties of less than 1 K while pointing at 21 directions. Temperature uncertainties of less than 1 K are achieved during nighttime up to a range of 8 km using a temporal resolution of 3 minutes and a range resolution of 300 m. The lidar resolves also turbulence in the convective boundary layer, e.g., at 470 m height with a temporal resolution of 10 s and statistical uncertainties of only 0.41 K. In addition to temperature, also the particle backscatter coefficient and the particle extinction coefficient are measured independently. The instrument operates with a primary wavelength of 355 nm. This has instrumental advantages compared to 532 nm but also yields eye-safety beyond a range of 500 m which facilitates the deployment. Highly efficient spectral separation of the atmospheric backscatter signals is performed by a polychromator with narrow-band interference filters in a sequential setup. The spectral characteristics of these filters were optimized with respect to high measurement performance in the daytime planetary boundary layer and the lower free troposphere. Pioneering measurements of the 2-dimensional temperature distribution in the lower troposphere in the vicinity of a mountain ridge are presented.