Intercomparison of aerosol measurements performed with multi-wavelength Raman lidars, automatic lidars and ceilometers in the framework of INTERACT-II campaign

Abstract

Abstract. Following the previous efforts of INTERACT (INTERcomparison of Aerosol and Cloud Tracking), the INTERACT-II campaign used multi-wavelength Raman lidar measurements to assess the performance of an automatic compact micro-pulse lidar (MiniMPL) and two ceilometers (CL51 and CS135) in providing reliable information about optical and geometric atmospheric aerosol properties. The campaign took place at the CNR-IMAA Atmospheric Observatory (760 ma.s.l.; 40.60∘ N, 15.72∘ E) in the framework of ACTRIS-2 (Aerosol Clouds Trace gases Research InfraStructure) H2020 project. Co-located simultaneous measurements involving a MiniMPL, two ceilometers and two EARLINET multi-wavelength Raman lidars were performed from July to December 2016. The intercomparison highlighted that the MiniMPL range-corrected signals (RCSs) show, on average, a fractional difference with respect to those of CNR-IMAA Atmospheric Observatory (CIAO) lidars ranging from 5 to 15 % below 2.0 km a.s.l. (above sea level), largely due to the use of an inaccurate overlap correction, and smaller than 5 % in the free troposphere. For the CL51, the attenuated backscatter values have an average fractional difference with respect to CIAO lidars < 20–30 % below 3 km and larger above. The variability of the CL51 calibration constant is within ±46 %. For the CS135, the performance is similar to the CL51 below 2.0 kma.s.l., while in the region above 3 kma.s.l. the differences are about ±40 %. The variability of the CS135 normalization constant is within ±47 %. Finally, additional tests performed during the campaign using the CHM15k ceilometer operated at CIAO showed the clear need to investigate the CHM15k historical dataset (2010–2016) to evaluate potential effects of ceilometer laser fluctuations on calibration stability. The number of laser pulses shows an average variability of 10 % with respect to the nominal power which conforms to the ceilometer specifications. Nevertheless, laser pulses variability follows seasonal behavior with an increase in the number of laser pulses in summer and a decrease in winter. This contributes to explain the dependency of the ceilometer calibration constant on the environmental temperature hypothesized during INTERACT.

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

“…Madonna et al (2015) compared ceilometers by Lufft (CHM15k), Vaisala (CT25k) and Campbell (CS135s) in the framework of IN-TERACT (Potenza, Italy) but did not consider water vapor absorption quantitatively. To our knowledge, Markowicz et al (2008) were the first to apply a correction term for water vapor absorption to data from a Vaisala CT25k ceilometer before deriving aerosol optical properties. Wiegner et al (2014) discussed the problem in a general way on the basis of simulated signals and proposed an improved approach to correct for water vapor absorption.…”

Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

“…The task of observations in lidar networks is to monitor the optical and microphysical properties of aerosol, which requires restoring not only the backscattering coefficient but also the lidar ratio and attenuation. Therefore, a large number of lidars are designed as aerosol-Raman (Althausen et al, 2000;Whiteman et al, 2007;Reichardt et al, 2012;Groß et al, 2015; Haarig et al, 2017;Madonna et al, 2018) or multiwave highspectral-resolution lidars (HSRLs; Eloranta, 2005;Burton et al, 2015). Most of these lidars use dichroic beam splitters as wavelength dividers, and polarizing elements (film po-larizers) are installed after the beam splitters and deflecting mirrors (Nott et al, 2012;McCullough et al, 2018).…”

“…It can be caused by aerodynamic forces arising from the free fall of particles (Kaul and Samokhvalov, 2005). Sections with the horizontal orientation of particles manifest in occurrence of sun glare when observing cloud cover from space (Chepfer et al, 1999;Masuda and Ishimoto, 2004). Analysis of the glare width shows the correspondence to the Gaussian distribution of crystal inclination with the half-width of about 0.4 • (Breon and Dubrulle, 2004;Lavigne et al, 2008).…”

Scanning Polarization Lidar LOSA-M3: Opportunity for Research of Crystalline Particle Orientation in the Clouds of Upper Layers

“…The task of observations in lidar networks is to monitor the optical and microphysical properties of aerosol, which requires restoring not only the backscattering coefficient, but also the lidar ratio and attenuation. Therefore, a large number of lidars are designed as aerosol-Raman (Reichardt et al, 2012;Madonna et al, 2018;Whiteman et al, 2007;Groß et al, 2015) or multiwave high spectral resolution lidars (HSRL) (Burton et al, 2015; Haarig et al, 2017;Althausen et al, 2000;Eloranta, 2005). Most of these lidars use dichroic beamsplitters as wavelength dividers, and polarizing elements (film polarizers) are installed after the beamsplitters and deflecting mirrors (McCullough et al, 2018;Engelmann et al, 2016;Nott et al, 2012).…”