Abstract
Abstract. A unique data set derived from remote sensing, airborne, and ground-based in situ measurements is presented. This measurement report highlights the known complexity of comparing multiple aerosol optical parameters examined with different approaches considering different states of humidification and atmospheric aerosol concentrations. Mie-theory-based modeled aerosol optical properties are compared with the respective results of airborne and ground-based in situ measurements and remote sensing (lidar and photometer) performed at the rural central European observatory at Melpitz, Germany. Calculated extinction-to-backscatter ratios (lidar ratios) were in the range of previously reported values. However, the lidar ratio is a function of the aerosol type and the relative humidity. The particle lidar ratio (LR) dependence on relative humidity was quantified and followed the trend found in previous studies. We present a fit function for the lidar wavelengths of 355, 532, and 1064 nm with an underlying equation of fLR(RH, γ(λ))=fLR(RH=0,λ)×(1-RH)-γ(λ), with the derived estimates of γ(355 nm) = 0.29 (±0.01), γ(532 nm) = 0.48 (±0.01), and γ(1064 nm) = 0.31 (±0.01) for central European aerosol. This parameterization might be used in the data analysis of elastic-backscatter lidar observations or lidar-ratio-based aerosol typing efforts. Our study shows that the used aerosol model could reproduce the in situ measurements of the aerosol particle light extinction coefficients (measured at dry conditions) within 13 %. Although the model reproduced the in situ measured aerosol particle light absorption coefficients within a reasonable range, we identified many sources for significant uncertainties in the simulations, such as the unknown aerosol mixing state, brown carbon (organic material) fraction, and the unknown aerosol mixing state wavelength-dependent refractive index. The modeled ambient-state aerosol particle light extinction and backscatter coefficients were smaller than the measured ones. However, depending on the prevailing aerosol conditions, an overlap of the uncertainty ranges of both approaches was achieved.
Highlights
Aerosol particles can sensitively influence the Earth’s radiation budget by scattering and absorption of solar radiation
Between 1200 and 1800 m altitude, a layer is indicated by a constant NCPC of around 4000 cm−3 and a NOPSS of around 55 cm−3
In the layer from 700 to 0 m altitude, NCPC steadily increases towards the ground up to 5000 cm−3, while NOPSS scatters around 45 cm−3
Summary
Aerosol particles can sensitively influence the Earth’s radiation budget by scattering and absorption of solar radiation. In situ aerosol measurements with unmanned aerial vehicles (UAV; Altstädter et al, 2018), helicopter-borne payloads, e.g., with the Airborne Cloud Turbulence Observations System (ACTOS; e.g., Siebert et al, 2006; Ditas et al, 2012; Wehner et al, 2015; Düsing et al, 2018), tethered-balloon payloads (e.g., Ferrero et al, 2019; Brunamonti et al, 2021), and zeppelins (e.g., Rosati et al, 2016b) are important experimental approaches to provide vertically resolved insight into the relationship between aerosol microphysical properties, chemical composition, optical properties, and related radiative effects Remote sensing techniques such as light detection and ranging (lidar) allow the profiling of aerosol optical properties with a high vertical and temporal resolution in a complementary way (Weitkamp, 2005). They can be used for the validation of lidar-based retrievals of, e.g., the absorption
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