The dual-field-of-view polarization lidar technique: a new concept in monitoring aerosol effects in liquid-water clouds – case studies

Abstract

Abstract. In a companion article (Jimenez et al., 2020), we introduced a new lidar method to derive microphysical properties of liquid-water clouds (cloud extinction coefficient, droplet effective radius, liquid-water content, cloud droplet number concentration Nd) at a height of 50–100 m above the cloud base together with aerosol information (aerosol extinction coefficients, cloud condensation nuclei concentration NCCN) below the cloud layer so that detailed studies of the influence of given aerosol conditions on the evolution of liquid-water cloud layers with high temporal resolution solely based on lidar observations have become possible now. The novel cloud retrieval technique makes use of lidar observations of the volume linear depolarization ratio at two different receiver field of views (FOVs). In this article, Part 2, the new dual-FOV polarization lidar technique is applied to cloud measurements in pristine marine conditions at Punta Arenas in southern Chile. A multiwavelength polarization Raman lidar, upgraded by integrating a second polarization-sensitive channel to permit depolarization ratio observations at two FOVs, was used for these measurements at the southernmost tip of South America. Two case studies are presented to demonstrate the potential of the new lidar technique. Successful aerosol–cloud-interaction (ACI) studies based on measurements with the upgraded aerosol–cloud lidar in combination with a Doppler lidar of the vertical wind component could be carried out with 1 min temporal resolution at these pristine conditions. In a stratocumulus layer at the top of the convective boundary layer, we found values of Nd and NCCN (for 0.2 % water supersaturation) ranging from 15–100 and 75–200 cm−3, respectively, during updraft periods. The studies of the aerosol impact on cloud properties yielded ACI values close to 1. The impact of aerosol water uptake on the ACI studies was analyzed with the result that the highest ACI values were obtained when considering aerosol proxies (light-extinction coefficient αpar or NCCN) measured at heights about 500 m below the cloud base (and thus for dry aerosol conditions).

Wildfire smoke, Arctic haze, and aerosol effects on mixed-phase and cirrus clouds over the North Pole region during MOSAiC: an introduction

“…Once in the UTLS height range, smoke particles become quickly distributed over large parts of the Northern Hemisphere within a few weeks, as observed and documented for the first time in 2001 (Fromm et al, 2008) and recently confirmed after the record-breaking Canadian fires in the summer of 2017 (Khaykin et al, 2018;Baars et al, 2019). In the case of the strong Siberian fires, the smoke particles probably became quickly distributed over the entire Arctic region (as suggested by the satellite observations presented by Johnson et al, 2021) and then remained in the UTLS height range for months. The decay of smoke-related stratospheric perturbations usually takes more than a half year (Baars et al, 2019).…”

“…Extreme and long-lasting wildfires in central and eastern Siberia, in closest neighborhood to the Arctic region, were most probably responsible for the UTLS smoke layer over the High Arctic in the winter half year of -2020(Johnson et al, 2021Ohneiser et al, 2021). The main burning phase lasted from 19 July to 14 August 2019.…”

CALIPSO Aerosol-Typing Scheme Misclassified Stratospheric Fire Smoke: Case Study From the 2019 Siberian Wildfire Season

“…Two telescopes (receiver sub-units) permit near-field and far-field observations. The co-polarized signal components, required to determine profiles of depolarization ratios, are obtained from the difference of the total minus the cross-polarized signal component (after careful correction of all instrumental influences on the signals) (Engelmann et al, 2016;Jimenez et al, 2020).…”

Hemispheric contrasts in ice formation in stratiform mixed-phase clouds: Disentangling the role of aerosol and dynamics with ground-based remote sensing

“…Hence, the free tropospheric aerosol is predominantly of marine origin with low concentrations overall. First results of the DACAPO-PESO campaign regarding events of significant aerosol load (Ohneiser et al, 2020;Floutsi et al, 2021), liquid cloud microphysics (Jimenez et al, 2020) and integrated water vapor observations (Bromwich et al, 2020) are already published. Observations at Leipzig were performed before October 2016 and between the deployments to Limassol and Punta Arenas.…”