RAMSES: German Meteorological Service autonomous Raman lidar for water vapor, temperature, aerosol, and cloud measurements

Abstract

The Raman lidar for atmospheric moisture sensing (RAMSES) for unattended, continuous multiparameter atmospheric profiling is presented. A seeded frequency-tripled Nd:YAG laser serves as the light source. A nine-channel polychromator, nonfiber coupled to the main telescope (790 mm diameter), is used for far-range measurements. Near-range observations are performed with a three-channel polychromator, fiber coupled to a secondary telescope (200 mm diameter). Measurement parameters are water-vapor mixing ratio (MR), temperature, and the optical particle parameters, which are extinction coefficient, backscatter coefficient, lidar ratio, and depolarization ratio at 355 nm. Profiles of water-vapor MR are measured from close to the surface up to 14 km at night and 5 km during the day under favorable atmospheric conditions in 20 min. Temperature profiles of the troposphere and lower stratosphere are determined with the rotational-Raman technique. For the detection of the rotational Raman signals, a new beamsplitter/interference-filter experimental setup is implemented that is compact, robust, and easy to align. Furthermore, the polychromator design allows two independent methods for calibrating measurements of depolarization ratio. RAMSES optical design concept and experimental setup are detailed, and a description of the operational near-real-time data evaluation software is given. A multiday observation is discussed to illustrate the measurement capabilities of RAMSES.

An overview of the first decade of Polly<sup>NET</sup>: an emerging network of automated Raman-polarization lidars for continuous aerosol profiling

“…Vertical profiles of aerosol properties up to 20 km height can be derived with this receiver unit. Additionally, profiles of the water-vapor mixing ratio can be determined via the measurement of the inelastic water-vapor backscatter at 407 nm wavelength (Reichardt et al, 2012;Foth et al, 2015). Below about 600-800 m a.g.l.…”

The automated multiwavelength Raman polarization and water-vapor lidar Polly<sup>XT</sup>: the neXT generation

“…Tech., 9, 1767-1784, 2016 www.atmos-meas-tech.net/9/1767/2016/ > 700 > 700 > 800 > 800 > 1000 > 800 1064 total 1.03 ± 0.02 0.80 ± 0.03 1.08 ± 0.02 0.94 ± 0.04 1.13 ± 0.03 to be measured data analysis under the assumption of pure Rayleigh depolarization in an aerosol-free height range (Behrendt and Nakamura, 2002). However, this method includes large uncertainties (e.g., Reichardt, 2003). An alternative method is the 90 • -calibration (formerly known as ±45 • -calibration, Freudenthaler et al, 2009b;Freudenthaler, 2016).…”

“…Therefore, the optical paths behind the field stop were designed in such a way that the spread of incident angles of the radiation is below 0.6 • at the interference filters so that a heightindependent transmission is assured (e.g., Reichardt et al, 2012). Also, the primary mirror is optically imaged onto the photocathodes of the PMTs to prevent height-dependent receiver efficiencies because of detector-surface inhomogeneities .…”

Water vapor observations up to the lower stratosphere through the Raman lidar during the Maïdo Lidar Calibration Campaign

“…In particular, preliminary results on the accuracy of Raman water vapor measurements in the UTLS have been obtained (Whiteman et al, 2011b(Whiteman et al, , 2012Leblanc et al, 2012), and different calibration methodologies have been developed Leblanc et al, 2011;Hoareau et al, 2009;Dionisi et al, 2010;Reichardt et al, 2012, Bock et al, 2013. The aim is to set up a lidar reference network for upper-air climate observations of water vapor such as GRUAN (GCOS Reference Upper-Air Network, Immler et al, 2010).…”